CAPITULO CUARTO
Chapter Six
Water
Executive Summary Both surface water and groundwater in the border region are generally scarce. Annual precipitation in the region is 71 percent lower, on average, than in Mexico overall. While a resident of the state of Chiapas has at his or her disposal 46.6 cubic meters of water per day (17,000 cubic meters of water per year), a person living in Baja California has only 274 liters per day (100 cubic meters per year), that is to say only 0.6 percent of the water available to the Chiapas resident. In 1996, per capita water withdrawal in the country was 6.37 times higher than in the border region. This data clearly shows the poor availability of this precious liquid in the border region. In 1996, 12 percent of the population of the border zone (694,151 people) did not have access to potable water. This population lives predominantly in marginal communities of the urban centers and in rural areas. The majority of municipalities in the border zone, 56 percent, get their water exclusively from deep wells. As a consequence, there is excessive exploitation of subterranean aquifers, a fact that has repercussions for the diminishing supply of water, the increasing costs of pumping, sinking wells and desalinizing water. The total volume of water withdrawn per day depends on the concentration of population and industrial and agricultural development for each of the municipalities analyzed in this report. Priority one municipalities extract 72.6 percent of all water withdrawn on the border. Together these municipalities account for 76.8 percent of the population of the border region, 76.2 percent of the maquiladora licenses, and 65.1 percent of the maquiladora jobs nationwide. In 1996, the three most heavily populated border cities, Tijuana and Mexicali in Baja California and Juárez in Chihuahua, withdrew the greatest volumes of water in the border zone. In that year those three cities withdrew more than 50 percent of the total volume of water withdrawn by the priority one cities. Mexicali also has intense agricultural activity. The fact that 88.1 percent of homes in the priority one cities have water service connections does not necessarily mean that they all had access to potable water. There are some municipalities that only have the infrastructure to provide water two or three times a week even though they have a sanitary water supply system. Although infrastructure for metering the consumption of water has been developed in 69 percent of water systems, only 66 percent of water users in these systems are subject to some kind of charges for water. This is due to the fact that some meters don’t work and because there are administrative deficiencies in the billing system (lack of infrastructure for keeping track of consumers and billing). For the municipalities for which we were able to obtain information, we found that the agencies that administer water operate at a deficit, 135
Report on the state of the environment and natural resources on Mexico's northern border
even when we consider only the established water rates and the cost per cubic meter of water provided. When the significant delays in billing are added, the deficits are even greater. The administration of water, the lack of resources available to provide infrastructure, the costs of operation, and pricing policies are complex matters with social repercussions that directly affect the quality of services provided and prevent the agencies that operate and administer water from being self-sufficient and sustainable. These circumstances also facilitate the irresponsible use of a vital resource in a region characterized by its scarcity. In 1994, the Río Bravo/Río San Juan river basin had a discharge of BOD (biochemical oxygen demand) of 379.8 tons per day, of which 51 percent was municipal discharge (195 tons per day) and 49 percent was industrial discharge (185 tons per day) This is particularly important because the more than 1.5 million people who live in the border municipalities of the state of Tamaulipas depend on water from this river. Wastewater treatment systems in 11 of the priority one municipalities account for 27.3 percent of the wastewater treatment capacity on the northern border. At the same time, these plants treat 24.5 percent of the overall volume of water treated in the border states. Several of the plants were built by the private sector. However, we should consider that 80 percent of the volume of treated water is treated in only three cities (Tijuana, Mexicali and Nuevo Laredo). It is also worth considering that six of these 11 municipalities treat a considerable quantity of wastewater in relation to the overall amount of water used. (between 25 percent and 84 percent).
Water Water is a vital resource for the health and life of people, as well as for wildlife. It is economically and socially essential. As population has grown and industry has developed, the demand for water has also grown, but the amount of available water has not changed. This has caused the management of water to become complex and conflictive, a situation further aggravated by natural phenomena, such as drought.1 This situation is even more extreme along the northern border of Mexico, where water is generally less available than in the rest of the country. In various sub-regions of the border area, such as arid and semi-arid zones, the situation is even more extreme.
1
Fig. 6.1. Availability of water (1997)
1200 800 172.6 400 0 Surface water
Source: CNA, 1997.
National Commission on Water. Hydraulics Program 1995-2000.
136
1473.7
1301.1
1600 Millions of m3 /day
The northern border reflects the distribution of population in the country overall. Ninety-two percent of the overall population of the 79 border municipalities is concentrated in 25 urban centers, 16 of which are located directly on the border with the United States. The rest of the population, 8 percent, resides in 15,127 localities. The fact that people are dispersed in rural areas creates water storage problems. As of December 31, 1996, 694,151
Groundwater
All water
Water
people in the municipalities studied by this report lived without access to potable water (see annex 5).2 That statistic corresponds to 12 percent of the overall population for that year. Most people without potable water lived in marginal areas of the largest cities or in rural areas. Fresh water comes from surface bodies (lakes, ponds, rivers and dams) and subsurface aquifers. The latter are created by natural, renewable recharges or infiltration of irrigation water. The temporary nature and scarcity of rain, along with run-off on the northern border do not generally allow the supply of water to meet the demand, and for that reason water from the subsoil must be withdrawn. According to estimates by the National Water Commission, the volume of surface water available in 1997 was 1,301.1 million cubic meters per day. For 1994, the annual recharge of groundwater was on the order of 172.6 million cubic meters per day.
Average Recharge per Day of Subterranean Aquifers
Millions of m3 per day
Figure 6.2 shows the volume of Fig. 6.2. Average daily recharge of aquifers (1994) recharge of groundwater (daily 172.6 average for 1994) as estimated 200 by the National Water Commission. As we can see, 61.9 160 106.85 percent of the total recharge is 120 65.75 available water and of that 61.5 80 percent is withdrawn. Of the 65.8 million cubic meters of ground40 water withdrawn daily nationwide, 0 1.6 percent is used by the border Annual recharge Annual extraction Available water municipalities. However, if we consider only the 269 aquifers of Source: CNA, 1996. the three hydrologic regions of the northern part of the country (northeast, north and northwest) which are distributed over 14 states, then 9.6 percent of water used from these aquifers is used by the border municipalities. In 1994, the 269 aforementioned aquifers represented3 only 18.5 percent of the annual recharge of the country. Almost of all this available water, 98.6 percent, was withdrawn. Regarding the use of groundwater, it is important to mention that in many cases aquifers are overexploited, with resulting increases in the costs of pumping, and other problems such as sinkholes and the need to desalinate water. As of 1995, 80 of the 459 known aquifers had problems of overexploitation, that is to say more than 20 percent were overexploited and of those, 57 (71.3 percent) were in the northern part of the country. In this sense, almost half the average volume per day of water withdrawn by these cities comes from the ground. Of the 79 municipalities included in this report, 44 (55.7 percent) rely exclusively on deep wells. On the other hand, 65.2 percent of the total recharge of all the aquifers in the country is found in the southeastern part of the country (42.0 million cubic meters per day). The average rainfall for the country is 777 mm per year, or 4,169.9 cubic meters per day. Although the average precipitation for the border area is estimated at 225 mm/year, we 2 3
“Access to water” refers to piped-in water at the home-site. . National Commission on Water, 1996, in “Federal Executive Power, Hydrologic Program, 1995-2000, Mexico.”
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Report on the state of the environment and natural resources on Mexico's northern border
should emphasize that in a large part of the area the annual rate fluctuates between 50 and 150 mm/ year. That number is equivalent to 193.76 cubic meters per day. It is worth mentioning that in spite of the fact that the border zone occupies 16 percent of the national territory, only 4.6 percent of the overall precipitation falls within the region. It is important to consider not only the total quantity of water that the country receives annually in the form of rain, but also how the rainfall is distributed over the year and over consecutive years, as well as terrain conditions and characteristics by latitude. For example, a person living in Chiapas has at his or her disposal 46.6 cubic meters of water per day (17,000 cubic meters per year) while a resident of Baja California has only 274 liters per day (100 cubic meters per year) or only 0.6 percent of water available to the resident of Chiapas.
Withdrawal and Uses of Water
Percentage
Figure 6.3 presents the Fig. 6.3. Consumptive uses of water in Mexico (1995) 4 withdrawal and uses of water in Mexico during 1995. In it we 83.3 100 present only data referring to 80 consumptive use5 since these statistics are the ones that directly 60 impact the availability of water. 40 The total volume of water 11.6 3.4 1.7 withdrawn in Mexico in 1995 for 20 consumptive and non0 consumptive uses was 5.61 cubic Aquaculture Agriculture Domestic Industrial meters per resident per day. If we consider only the consumptive Source: CNA, 1996. uses (agriculture, domestic use, industry and aqua-culture) the total volume for the same year was 2.21 cubic meters per resident, per day. Of the total volume of water withdrawn for consumptive use, 83.3 percent (167.67 million cubic meters per day) was used for agriculture; 11.6 percent (23.3 million cubic meters per day) was for domestic use; 3.4 percent was used by industry and 1.7 percent for intensive aquaculture. It’s important to point out that the amount of water for agriculture was 7.2 times that used for domestic purposes. Of the total volume of water withdrawn, 249.2 liters/person/day were available for domestic use, versus an average of 1.84 cubic meters per day for agriculture. Water coming from subterranean aquifers has diverse consumptive uses: agricultural, domestic, commercial and industrial. It is often the case that water used by urban centers (domestic, commercial and industrial) is secondarily used for irrigating agriculture, even though it has not been sufficiently treated. The major use of surface water is agriculture and, in the cities that depend on surface water, urban uses. It is important to mention that surface water, after having been used by cities, is often reused to irrigate fields and even as potable water in other locations in the basin below the Río Bravo (Rio Grande). For example, all of the cities bordering this river, from Ojinaga, Chihuahua to Matamoros, Tamaulipas receive 4 5
Total withdrawal: includes the withdrawal of surface and groundwater Consumptive use: impacts the availability of water because of the water used, only part of it is returned. Non-consumptive use: The total amount of water used is returned (generation of electric energy).
138
Water
all or part of their supply of water from this river. In the state of Baja California there is a great dependence on water from the Colorado River. In order to reach Tijuana, that water has to be pumped over the La Rumorosa mountain range at an altitude of 1,100 meters above sea level. After conquering this obstacle, the waters of the Colorado are stored in the El Carrizo reservoir and are pumped across the 125.47 kilometer-long Rio Colorado-Tijuana aqueduct. Moving the water requires six pumping stations. The aqueduct has a capacity of 4 cubic meters per second. Fig. 6.4. Total volume of water withdrawn in the northern border states of Mexico (1996) 1068.5
1200 1000
Thousands of m3
Figure 6.4 shows the total volume of water withdrawn for consumptive uses in the northern border of Mexico during 1996. A total of 5,608,857 cubic meters per day were withdrawn, which is the equivalent of 347 liters per resident per day. The total withdrawal of water per resident in the northern border was less than one-sixth the national average. This clearly shows the poor availability of this precious liquid in the border states.
1070.4
998.7 844.1
802.8
824.2
800 600 400 200 0 B.C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Source: INEGI, 1997.
The states that withdraw the most water per year are Sonora and Chihuahua. The volume of water withdrawn by these two states accounts for 38.2 percent of the total water withdrawn in 1996 in the northern border of the country. Baja California consumes the least amount, accounting for 14.3 percent of the total volume of water withdrawn. However, as we shall see in the next graph (6.5), the panorama appears different when we consider the average amount of water used per resident per day. Fig. 6.5. Average per capita daily withdrawal of water. Northern border states of Mexico (1996)
0.2
0.311
0.266
0.373
0.3
0.342
0.4
0.362
0.484
0.5 Cubic meters
Sonora is the border state with the highest volume of water withdrawn per resident per day, with 484 liters. Next is Coahuila with 373 liters per day, and following that, Chihuahua, with 362 liters per day. Nuevo Leon has the lowest water usage per resident with only 266 liters per day. While the amount of water withdrawn for consumptive uses in Sonora is less than one-fourth the national average, in Nuevo Leon it is less than one-eighth the national average.
0.1 0
B.C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Projected population in 1996, based on the average annual growth rate from 1990 to 1995. Source: INEGI, 1995; INEGI, 1997.
The water supply in the northern border region comes from 2,318 deep wells, 122 springs and 805 other sources, including direct taps into the hydraulic network, dams, aqueducts and surface water infiltration galleries in Baja California. In Sonora sources include surface water infiltration galleries, seeps and hand-dug wells; in Chihuahua they include rivers, dams, surface water infiltration 139
Report on the state of the environment and natural resources on Mexico's northern border
galleries and mines; in Coahuila, rivers and surface water infiltration galleries; in Nuevo Leon, rivers, dams, surface water infiltration galleries and taps into the aqueduct; and in Tamaulipas, river, dams and surface water infiltration galleries. Of the total volume of water withdrawn by the border states, 58.6 percent comes from deep wells, 1.5 percent comes from springs, and 41.7 percent comes from other surface sources. Fig. 6.6. Sources of water in the northern border states (1996) Springs
Others 88.8
Deep wells
Coahuila
Nuevo León
8.8 2.4
1.3
19.6 1.3
Chihuahua
30
79.1
Sonora
1.1
Baja California
2.9
0.7
0
0.1
40 20
68.7
96.0 23.7
60
75.6
61.1
80 38.8
Percentage
100
Tamaulipas
Source: INEGI, 1997.
Figure 6.6 shows the different sources of water in each of the border states. As can be seen, Baja California predominantly obtains water from sources other than deep wells or springs, the states of Sonora, Chihuahua and Coahuila rely predominantly on groundwater (deep wells), and Nuevo Leon and Tamaulipas rely predominantly on rivers and dams. While more than 96 percent of the water used by Chihuahua comes from deep wells, this source only represents 8 percent of the water supply for Tamaulipas.
The Río Bravo (Rio Grande) Basin The Río Bravo basin is very important to the border zone. Given that the basin covers an area of 226,275 square kilometers in five states (Chihuahua, Coahuila, Nuevo Leon, Tamaulipas and Durango), an area which is home to approximately 9 million people, what happens to the river basin has a direct impact on the communities that live in the lower part, principally in the border cities in state of Tamaulipas, where more than 1.5 million people depend on water from this river. Furthermore, 80 percent of the surface water used for agriculture comes from the river. Until 1996, three urban centers in Tamaulipas (Gustavo Ordaz, Reynosa and Matamoros) were supplied with water from the irrigation canals, which were in turn supplied with water from the Río Bravo. From 1996 on, these cities began to get water directly from the river, eliminating the use of canals during the seasons when water wasn’t needed for irrigation, and avoiding the consequent loss of water caused by that practice. Field investigations indicate that total volume of water withdrawn in 1998 was around 371,500 cubic meters per day, which represents a withdrawal per resident on the order of 0.33 cubic meters per day.
140
Water
Figure 6.7 shows the total volume of water withdrawn by the border cities, organized by the four categories defined in this report.
Table 6.1. Cities supplied entirely or partially by Rio Grande water (1996) City
Population
Volume withdrawn, 3 m /day
m /capita/día
88,821
26,000
0.293
120,398
87,000
0.723
Cd. Acuña Piedras Negras
3
116.16
Reynosa
N. Laredo
166.68 34.00
88.00
Matamoros
P. Negras
Acuña
Ojinaga
Juárez
Ascensión
4.26
23.74
74.67
S.L. Col.
1.11
Nogales
25.16
A. Prieta
Tijuana
0
Naco
100
80.19
200
128.74
343.82
239.55
300
Mexicali
Thousands of cubic meters
400
As we see here, Ciudad Juárez, Chihuahua, extracts the greatest volume of water (343,820 cubic meters per day). Juárez accounts for 23.9 percent of the population of the priority one cities, and has the highest concentration of maquiladora industry jobs on the national level (see Appendix 3). Mexicali also stands out because its population is only 69.7 percent the size of the Tijuana’s, yet in
306.36
Thousands of cubic meters
The total volume of water Nuevo Laredo 288,995 128,727 0.445 withdrawn per day in each of Nva. Cd. Guerrero 3,918 1,260 0.322 the categories reflects the Cd. Mier 6,275 1,841 0.274 population, industrial develCd. Miguel Alemán 22,581 6,876 0.304 opment and agricultural development of each of the G. Díaz. Ordaz 15,327 2,950 0.192 categories. For example, Río Bravo 101,736 25,583 0.251 72.6 percent of the daily Reynosa 350,023 114,747 0.328 volume of water withdrawn in Matamoros 377,915 166,072 0.439 the border zone is withdrawn by the 14 priority one Total 1,375,989 561,056 0.408 municipalities, which togeSource: Chávez, O.,1997. ther account for 76.8 percent of the population of the Fig. 6.7. Total water withdrawal in border municipalities (1996) region. When analyzing the 2000 140 average total of water withdrawn Volume extracted per municipality per day per municipality, what 120 1600 stands out that while the priority Average volume extracted per day 100 one municipalities withdrawn 1200 80 116,602.2 cubic meters per day, each of the priority four cities 60 800 withdrew, on average, only 40 3,151.4 cubic meters per day, 400 20 that is, only 2.7 percent of the 0 0 average withdrawn by the priority Priority 1 Priority 2 Priority 3 Priority 4 one cities. The 39 priority four municipalities account for only Source: INEGI, 1997. 8.4 percent of the total population of the border zone. Figure 6.8 shows the total amount of water withdrawn per day in the priority one municipalities. The information refers to water used Fig. 6.8. Total water withdrawn, priority one municipalities (1996) by residents of the municipal seat.
Source: INEGI, 1997.
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Report on the state of the environment and natural resources on Mexico's northern border
1996 it withdrew 27.9 percent more water than Tijuana. There are two fundamental reasons why: there is less water available in Tijuana, and there is a greater level of agricultural activity in Mexicali. Naco and Ascención extract the least amount of water among the priority one municipalities, due to the lack of water, low population, and high proportions of people living in a rural environment. Figure 6.9 shows the total average withdrawal of water per resident per day of people living in the municipal seat. The data does not necessarily show the amount consumed per resident.
0.42
0.32
Reynosa
N. Laredo
0.42
0.71
Matamoros
P. Negras
Acuña
0.30
Ojinaga
Juárez
0.20
Ascensión
S.L.R. Col.
Nogales
0.35
0.52
0.55
0.22
Naco
0.21
0.35
A. Prieta
0.41
Tijuana
Mexicali
Cubic meters per day
1.01
The average amount of water Fig. 6.9. Per capita withdrawal, priority one municipalities (1996) withdrawn per resident in the 1.2 priority one municipalities in 1996 1.0 was 349 liters per day. In this 0.8 graph we see that Ojinaga withdrawn 2.9 times more than 0.6 the median for the municipalities 0.4 of this priority and 5.1 times more 0.2 water than Ascensión. Even so, Ojinaga used on average less 0 than half (45.8 percent) of the water per resident used on the national level. After Ojinaga, Piedras Negras withdrew the Projected population in 1996, based on the average annual growth rate most water per resident – 705 from 1990 to 1995. liters per resident per day. The Source: INEGI, 1995; INEGI, 1997. large border cities that used the least amount of water were, from least to most, Tijuana, Baja California with 213 liters per resident per day; Juárez, Chihuahua, with 306 liters per resident per day; and Matamoros, Tamaulipas, with 320 liters per resident per day. Tijuana’s usage was less than one-tenth the national average; that of Juárez was one-seventh, as was that of Matamoros. Figure 6.10 shows the total daily volume of water utilized by each of the priority two municipalities. We see here that, in 1996, the municipality of Tecate, Baja California used 48.1 percent of the total volume of the 24 municipalities in this category. Although Tecate has about the same population as Caborca, Sonora, the latter used only 18.1 percent of the volume of water used by Tecate. Furthermore, the municipality of Río Bravo,Tamaulipas, which has a population 55.8 the size of the population of Tecate, used 18.9 percent of the water used by Tecate. At the same time, Río Bravo, Tamaulipas, used about the same amount of water as Caborca, even though its population is 23.3 percent of the population of Caborca. Camargo, Tamaulipas, also used about the same amount of water as Caborca, but its population is 54.7 percent greater than Caborca’s.
142
Water
Fig. 6.10. Volume of water withdrawn, priority two municipalities (1996)
148.4
120
28.0 7.1 Río Bravo
1.8
M.Alemán
Mier
Guerrero T.
G.D. Ordaz
1.3
3.7
27.8 4.1 Anáhuac
Camargo
11.0
Ocampo
5.0
3.0
Nava
2.0 Hidalgo
Jiménez
2.0
1.7
Guerrero C.
0.1
P.G. Guerrero
0.7
M. Benavides
Janos
1.1
0.6 Saric
Sta. Cruz
Guadalupe
0.4
14.5
3.1
P. Peñasco
Cananea
Altar
Coborca
Tecate
0
P.E. Calles
40
12.3
26.8
80
2.0
Cubic meters per day
160
Source: INEGI, 1997.
Among the priority two cities, Manuel Benavides, Chihuahua, used the least amount of water at 120 cubic meters per day. Figure 6.11 shows the average volume of water per resident per day used by the priority two cities. Fig. 6.11. Per capita daily water withdrawal by priority two municipalities (1996)
1.80 1.54
2.0
2.18
0.24
0.29
0.31
0.27
G.D. Ordaz
Mier
M. Alemán
Río Bravo
0.33
Guerrero T.
Camargo
0.22
0.46
Ocampo
Anáhuac
0.49
Jiménez
Hidalgo
Guerrero C.
0.18
P.G. Guerrero
0.06
M. Benavides
Janos
0.36
0.66 0.12
Guadalupe
0.26
Saric
0.25
Sta. Cruz
0.37
P. Peñasco
0.30
P.E. Calles
0.4.0
0.41
Cananea
0
Tecate
0.5
Coborca
0.28
1.0
Nava
0.95
1.5
Altar
Cubic meters
2.5
Projected population in 1996, based on the average annual growth rate from 1990 to 1995. Source:
INEGI, 1995; INEGI, 1997.
What stands out here is that Tecate, Baja California, besides using the greatest amount of water among the 79 municipalities studied by this report, has an average water usage per resident very similar to the national median (2.17 cubic meters per resident per day). Among priority two municipalities analyzed by this report, Manuel Benavides, Chihuahua used the least amount of water per resident in 1996, 55 liters per resident per day, an amount which is 36.3 times less than the amount of water used by Tecate and 36.8 times lower than the national average. Janos, Chihuahua, followed with 65 liters per resident. Hidalgo and Guerrero, Coahuila and Camargo, Tamaulipas, with 1.54, 0.95 and 1.80 cubic meters per resident per day respectively, stand out with their high water usage levels, as exceptions to the norm for the other cities in this category, which fluctuated between 115 and 494 liters per resident per day. Undoubtedly these large variations, independent of the
143
Report on the state of the environment and natural resources on Mexico's northern border
consumptive uses in each region, reflect the poor availability of water in the various regions of the border and the occasional excessive use of water in some areas. In the priority three and four municipalities (see Appendix 5), the average water usage per resident was 371 liters per day. While Coyame, Chihuahua used 88 liters per resident per day, Sabinas, Coahuila used 1.23 cubic meters per resident per day and Zaragoza, Coahuila, used 1.08 cubic meters per resident per day. To summarize, of the 79 municipalities analyzed for this report, the three which used the most water per resident were from most to least: Tecate, Baja California, Camargo, Tamaulipas and Guererro, Coahuila. All three are priority two cities. On the other hand, the three cities which used the least amount of water are, from least to most, Manuel Benavides, Janos and Coyame. All three are in Chihuahua. Just over one-third of the deep wells located in the northern border states are within municipalities and 45.1 percent of these are located in the 14 priority one municipalities (352 of the 781). Just over one-fifth of the wells within municipalities are in priority two municipalities, and the remaining 34 percent are in category three and four municipalities.
143
92.31
163
352
Number of wells
Thousands of m3 per day
Figure 6.12 shows the amount of Fig. 6.12. Groundwater withdrawal in border municipalities (1996) groundwater withdrawn by the 500 600 561.53 border municipalities in 1996. 500 Wells 400 Over half (52.2 percent) of the m3 per day 400 300 groundwater was withdrawn by 300 priority one municipalities. This 253.60 200 168.79 200 statistic coincides with the 123 100 concentration of population in 100 these cities. We should remem0 0 ber that the priority one cities Priority 1 Priority 2 Priority 3 Priority 4 have 76.8 percent of the Projected population in 1996, based on the average annual population of the municipal areas growth rate from 1990 to 1995. studied. Priority two municipal Fuente: INEGI, 1995; INEGI, 1997. areas accounted for 23.6 percent of the groundwater withdrawn; priority three municipalities accounted for 8.6 percent, and priority four municipalities accounted for 15.6 percent. In the priority one municipalities, deep wells withdrew on average 1,595.3 cubic meters per day. In the priority two municipal areas, the average was 1.555.8 cubic meters per day; the figures were 1,180.3 cubic meters per day for priority four and 750.5 cubic meters per day for priority three. Those figures correspond to 47 percent of the water withdrawn by priority two cities, 48.2 percent of the water withdrawn by the priority four cities and 63.6 percent of the water withdrawn by the priority three cities. These figures were presented by the National Institute of Statistics, Geography and Information (INEGI) in its annual report on the border states for 1997; however the numbers presumably refer to urban uses of water, since field work shows they significantly underestimate the total volume of water withdrawn.
Water for Domestic Use As we have already mentioned, 11.6 percent of the total water withdrawn in Mexico in 1996 was dedicated to domestic use. This percentage represents an average of 23.288 million cubic meters per day or 249.38 liters per resident per day. According to the National Water
144
Water
Commission,6 15 million Mexicans did not have access to potable water. Of that number, 694,151 lived in the municipalities of the northern border region. In addition, 33.2 percent of the total population lacks sewage systems. The available infrastructure has the capacity to disinfect 95 percent of the water administered to the population for domestic use, and 25.9 percent of this water passes through some processing to make it potable in one of the 356 water processing plants across the country. However, practically all of the bodies of water in the country are contaminated.7 In addition, the safety of water used for domestic purposes is affected by the social, demographic, educational and economic factors detailed in chapter three of this report, such as poverty, the low level of education, social atomization, inadequate hygiene and nutrition, rapid growth of metropolitan areas (population and industry), lack of infrastructure, lack of access to sewer systems, the contamination of aquifers and surface sources of water, as well as problems of access to availability of water. All of these are factors together explain why intestinal infections and their complications are the primary cause of illness in the border area and the fourth cause of death in children under four. Eight percent (2,256) of all deaths in the border area municipalities are due to infectious disease. Of these, 78.6 percent occur in the category one municipalities (see Appendix 4). With respect to infrastructure, as was described above, 12 percent of the total population living along the border zone does not have access to piped-in water, 46.3 percent does not have sewer lines connected to the public system, and almost 50 percent of the population lives in overcrowded conditions. In absolute numbers, approximately 60 percent of this population lives in marginal urban conditions in the 11 large cities located in the northern border region (cities with populations greater than 100,000). The great majority of these cities – 10 of the 11 – are priority one municipalities (see Appendix 1). Inventory of Potable Water Treatment Plants in the Northern Border States of Mexico Fig. 6.13. Water treatment plants in the northern border states (1995) 848.02
30
259.20
10 0
Sonora
3
3
46.657 B.C.
1000 800 600 400
22
20
512.76
450.14
86.40
Chihuahua Coahuila
11
40
42
Number of plants Installed capacity
19
Number of plants
50
N. León
Thousands of m3
In 1995, 287 (76.3 percent) of the 356 water treatment plants located in Mexico were operating. These operating plants had the capacity to treat 6,619,752 cubic meters of water per day, a figure that corresponds to 28.4 percent of all the water destined for domestic use. Figure 6.13 shows the location of water treatment plants by border state and their capacity in cubic meters per day.
200 0 Tamaulipas
Source: CNA, 1996.
Of the 287 plants that were operating in 1996, 100 were located in border states (34.8 percent). During 1995, these 100 plants processed 2.2 million cubic meters of water per day – one-third of all water treated on the national level. Tamaulipas processed 38.5 percent; Nuevo León, 23.3 percent; Baja California, 20.4 percent; and Sonora 11.8 percent, while the states of Coahuila and Chihuahua together processed only 6 percent. It is important to point out that only surface water destined for human consumption was treated; processing is not needed for groundwater. The large dependency on surface water, above all in the border zone, is 6 7
National Water Commission, 1996 Hydraulic Program, 1995-2000. Mexico. INEGI and SEMARNAP, 1997. Estadísticas del Medio Ambiente. México.
145
Report on the state of the environment and natural resources on Mexico's northern border
reflected in the high volume of water treated in the state of Tamaulipas. Another fact that may be related to this is that during 1996, the states of Nuevo León and Tamaulipas had lower general mortality and infant mortality rates from gastrointestinal illnesses than the rest of the border states (see Appendix 4).
Liters per resident
Figure 6.14 shows the volume of Fig. 6.14. Volumen de agua desinfectada, litros por día por habitante en estados de la frontera norte de México (1996) water disinfected per resident during 1996 in each of the 500 403 376 northern border states. In that 400 308 year in the country overall, 92.7 274 243 238 300 percent of water destined for domestic use (21.6 million cubic 200 meters per day) was disinfected, 100 most often by chlorination. Over one-fifth (21.6 percent) of the 0 B.C. Sonora Chihuahua Coahuila N. León Tamaulipas total volume was disinfected in the border states. Chihuahua Fuente: CNA, 1996. disinfected the largest volume of water destined for domestic use among the border states: 1.13 million cubic meters per day, or 403 liters per resident per day. Potable Water Service Connections As of Dec. 31, 1996, the northern border states had introduced a total of 3.4 million water service connections, of which 95 percent (3.2 million) were domestic. In this same year, 4.8 percent of the service connections were commercial and 0.3 percent were industrial. Figure 6.15 shows the distribution of domestic service connections in the border states. Nuevo León has the highest number, with 22.7 percent of the total. According to the figures, in Baja California, 93 percent of the households have service connections, making it the state with the greatest number of houses connected to this important public network. On the other hand, Tamaulipas had the lowest coverage in 1996, with 86 percent of households connected. Figure 6.16 shows the number of household service connections in each of the priority one municipalities and the coverage that represents in each.
800 0.93
0.92
593.01
600 493.22
No. of domestic connections Connections per household
448.27
400
0.94
730.29
0.92 0.90
523.30
0.9
432.03 0.88
0.87
0.86
0.87
0.86
200 0.84 0
0.82 B.C.
Source: INEGI, 1997.
146
Sonora
Chihuahua
Coahuila
N. León
Tamaulipas
No. connections per household
Thousands of domestic connections
Fig. 6.15. Domestic connections to public potable water systems in the northern border states (1996)
Water
Fig. 6.16. Domestic water connections in priority one municipalities (1996) 500
0.82
0.88
0.8 0.6
72.88
0.77
55.20
0.85
24.24
16.80
5.94
206.35 4.80
0.4 0.2
Reynosa
N. Laredo
Matamoros
P. Negras
0 Ojinaga
Ascensión
33.83 S.L.R. Col.
22.90 Nogales
11.98 A. Prieta
Tijuana
0 Mexicali
0.84
0.71
249.03
170.61
200
1
1.00
Acuña
0.64
0.82
Juárez
300
100
1.00 1.00
0.81
No. connections per household
69.17
No. domestic connections
0.99
Naco 1.40
400
1.2 0.98
Fuente: INEGI, 1997.
As of Dec. 31, 1996, 76.7 percent of the potable water domestic service connections in the 79 municipalites included in this report were located in the 14 priority two cities. San Luis Río Colorado, Sonora; Ascensión and Ojinaga, Chihuahua; Tijuana and Mexicali, Baja California, had practically all of their housing units hooked up to the potable water system, according to the annual statistics from the respective states. However, a field investigation showed that San Luis Río Colorado had the best coverage, with 99 percent of its housing units in the municipal seat hooked up in 1997. It is important to clarify that this information comes from the various agencies which provide water service, which, in the majority of cases, only consider housing units in the municipal seat, and possibly some semi-rural areas. In the following municipalities, 15 percent or more of housing units were not connected to potable water as of 1996: Naco (64 percent), Nogales (71 percent), and Agua Prieta (81 percent), Sonora; Matamoros (77 percent) and Nuevo Laredo (82 percent), Tamaulipas; Ciudad Juárez, Chihuahua (82 percent); and Acuña, Coahuila (84 percent). Table 6.2 Growth in the number of domestic connections (1996-1997) Municipality
Tijuana Tecate S.L.R. Colorado Nogales Cd. Juárez Cd. Acuña Piedras Negras Reynosa Matamoros Total
Domestic connections 1996 * 249,026 13,204 33,877 22,892 206,349 16,790 24,238 72,875 69,169 708,420
Domestic connections 1997 ** 267,612 14,484 40,500 23,500 228,275 18,612 24,910 98,420 69,650 785,963
Growth in number of domestic connections 7.46% 9.69% 19.55% 2.65% 10.63% 10.85% 2.77% 35.05% 0.70% 10.94%
Average annual population growth 6.54% 4.29% 4.09% 4.74% 5.34% 8.97% 3.66% 3.85% 3.97% 4.1%
Source: * INEGI, 1997. ** Field investigation.
These municipalities account for 57.5 percent of the all the domestic water service connections in the 79 municipalities included in this report. In Table 6.2, we see an average increase of 10.9 percent in the available water infrastructure between 1996 and 1997 in the selected municipalities. The most important improvement was in Reynosa, Tamaulipas 147
Report on the state of the environment and natural resources on Mexico's northern border
which, in only one year, saw an increase of 35 percent. Tecate, Baja California, considered within priority two, had an increase of 9.7 percent, which indicates a significant setback in the existing infrastructure. Since there is migration to urban centers, deficits in service continue, despite improvements in infrastructure.
0.81 0.87
0.95
1.00 0.87
1.00 1.00 0.98
1.00 0.85
5.92
4.02
0.4 0.2
2.07
1.22
3.64
1.02
2.10
4.73
5.30 0.15
1.90
0.28
0.40
1.64
2.09
Mier
G.D. Ordaz
Guerrero T.
Camargo
Anáhuac
Ocampo
Jiménez
Hidalgo
Guerrero C
P.G. Guerrero
M. Benavides
Jano
0.39
0.8
0 Guadalupe
0.32
0.45
0.27
1
0.6
0.47 0.46
Saric
P. Peñasco
P.E. Calles
Coborca
Cananea
Altar
0 Tecate
0.63
7.88
5.89
1.05
1.86
5
0.74
Nava
0.68 10.96
13.20
0.74
19.8
0.95
0.89
1.00
0.82
15 10
1.00
1.2
No. connections per household
Río Bravo
0.87
Sta. Cruz
20
No. domestic connections
M. Alemán
25
Connections per household
Thousands of connections
Fig. 6.17. Domestic water connections in priority two municipalities (1996)
Source: INEGI, 1997.
Figure 6.17 shows the distribution of domestic water service connections in the priority two municipalities. Here we see that in 1996, 25 percent of the priority two municipalities had all of their private housing units connected to the potable water system. The municipalities with complete covererage were Puerto Peñasco, Sonora; Hidalgo, Coahuila; Camargo, Guerrero, Mier and Miguel Alemán, Tamaulipas. Field work shows that Guerrero and Mier, Tamaulipas report 85 percent and 95 percent coverage in their municipal seats, respectively. Four municipalities in the state of Coahuila had less than 50 percent of their housing units connected to water: Guerrero, Jimenez, Nava and Ocampo. Of all the category two municipalities, Jiménez, Coahuila had the lowest percentage of housing units connected to potable water, with only 15 percent. Of the priority three and four municipalities, 56.4 percent had all of their housing units connected to domestic water service connections (see Appendix 5). In fact, the municipalities in this category had better coverage than those in the other two categories (94 percent on average). Figure 6.18 shows the percentage of domestic water service connections in the municipal seats that have meters in relation to the percentage of water that is billed in 13 border cities. While the infrastructure for metering water consumption is underdeveloped, the infrastructure for billing water service is even less developed, due to some percentage of meters not working, administrative deficiencies in the billing system, or both. This means that the presence of water meters does not necessarily assure that water usage is being billed to the consumer.
148
Water
Fig. 6.18. Percentage of domestic connections with meters and percentage of service that is billed (1998)
78
80
68
100
93
92
80
75
76 60
75 62
54
60
60 38
40
50
47
46
53
51
48
32
20
5 Camargo
Jiménez,
P. Negras
Acuña
Ojinaga
Juárez
S.L.R. Col.
Tecate
Ensenada
Tijuana
Mexicali
0 0
97
10 Río Bravo
Percentage
100
Percentage billed
Percentage of connections with meters 93
Matamoros
120
Fuente: Chávez O., 1998
For example, in the 13 municipalities for which we were able to obtain information, there are a total of 923,979 service connections (domestic, commercial and industrial). This statistic represents 71.6 percent of the total number of connections in the 79 border municipalities. Of that number, 68.6 percent (633,525) are metered, and 65.6 percent are subject to some type of billing for water service; they are either billed according to the water usage recorded by the meter, according to pre-established rates that don’t take into account actual usage, or in some cases, a rate established by annual average use. In the chart we see that in various municipalities the percentage of connections billed to the user surpasses the percentage of connections with meters. These municipalities include San Luis Río Colorado, Sonora; Ojinaga, Chihuahua; Acuña, Piedras Negras y Jiménez, Coahuila; Camargo, Matamoros; and Río Bravo in Tamaulipas. Table 6.3 shows the rate per cubic meter of water, the cost per cubic meter, the volume of water withdrawn per day, and the percentage of water that is billed. (The prices and costs are in Mexican pesos.) Although the data in the table is not exact, because the volumes of water withdrawn are for 1996, not 1998, and because the percentage of bills refers to the number of accounts and not to the volume of water provided per day, the table does show us the deficits in the water systems, with the exception of San Luis Rio Colorado. The agencies that administer water operate in a limited manner and in some cases at a deficit. Although in some cases there are operating surpluses, they are not enough to cover the costs of maintaining and improving the water system and therefore the systems rely on state and federal subsidies. The administration of water as a resource, the lack of resources to solve infrastructure problems, operating costs, pricing policies, the definition and setting of water rates, besides being complex issues which have social and economic repercussions, Tabla 6.3. Tarifas, costo y porcentaje de cobranza del servicio de agua 3
Municipalities SLR Colorado Juárez, Chih. Acuña, Coah. Piedras Negras Camargo, Tamps. Reynosa, Tamps. Río Bravo, Tamps.
Rate per m 1998 20.00 23.00 20.00 20.00 10.00 20.00 20.00
3
Cost per m servido 1998 15.00 28.00 26.00 40.00 19.00 26.00 22.00
Volume withdrawn, 3 m /day 1996 74,673 343,820 34,000 88,000 27,809 116,158 28,010
Percentage collected 1996 80 62 50 51 97 58 48
Surplus or deficit in peos per day 74,673.00 -4,724,086.80 -544,000.00 -2,622,400.00 -258,623.70 -1,672,675.20 -347,324.00
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Report on the state of the environment and natural resources on Mexico's northern border
directly affect the quality of services provided and limit the institutions the operate and administer water, keeping them from being self-sufficient and sustainable.
Biochemical Demand of Oxygen (BOD) According to the Hydraulic Program for 1995-2000, municipalities generate 20 million cubic meters of wastewater daily, but the sewage systems collect only 75.3 percent of that, that is to say 15.07 million cubic meters per day. The Biochemical Oxygen Demand (BOD) is an indicator of organic contamination (organic material and bacteria) in water. It is estimated that in 1998, the country’s population generated 1.8 million tons of BOD, of which 67.8 percent (1.22 million tons) were collected by sewage systems. Of the amount collected, only 12.3 percent (0.15 tons of BOD) were adequately treated. A study of BOD in contaminated discharges in selected river basins8 determined that in 1994, the Río Bravo/Río San Juan basin had a discharge of BOD of 379.8 tons per day, with 51.3 percent (194.8 tons per day) coming from municipalities and 48.7 percent (185 tons per day) coming from industry. It is important to point out that a percentage of the discharges into this basin are municipal discharges for the metropolitan area of Monterrey. In that same year, 3.8 percent of the total amount of discharges of industrial wastewater into selected river basins was into the Río Bravo/Río San Juan. It is estimated that for the year 2000, the total demand for potable water for domestic use will be 25.7 million cubic meters per day and 1.95 million tons of BOD will be generated. Of that total amount of BOD, 76.4 percent will be captured by sewers. Compared to 1997, there will be a 21.5 percent increase in demand for potable water and the increase in generation of BOD will be 8.3 percent, from 1.8 million tons in 1997 to 1.95 million tons in 2000. Sewage Systems in the Border Municipalities and States As of December 31, 1996, there were 324 sewage systems in the northern border states which serviced 326 of the 41,271 settlements in the region. These figures do not include information from the state of Nuevo León (due to lack of data). Baja California, Sonora, Chihuahua, Coahuila, and Tamaulipas covered 79 percent of their settlements. However, we should consider that 97.6 percent of the 41,271 towns are too small to have a sewage system (less than 500 inhabitants). Taking into consideration the fact that only settled areas with 500 or more residents have sewage systems (991 locations), then only 32.9 percent of settlements have these services. The 14 priority one municipalities have 25 systems. They serviced 24 of the 5,399 settlements that are within the priority one municipalities. Deducting the number of settlements with less than 500 inhabitants (5,270) from the total, we conclude that sewage systems covered 18.6 percent of the 129 settlements with 500 or more residents. The 23 priority two municipalities (not including Anahuac, Nuevo León) have 37 sewage systems that cover 37 of the 3,959 settlements. The systems cover 52.9 percent of settled areas with 500 or more people. We should point out that all medium and large urban centers have sewage systems.
8
National Water Commission, 1996. Diagnosis of Environmental Health Actions on the National Level, Mexico, 1996.
150
Water
Municipal Wastewater Treatment Plants On the national level, the capacity of wastewater treatment plants increased by 3,369,600 cubic meters per day from 1988 to 1996. In 1996, there were 787 municipal wastewater treatment plants in the country, which treated 4,561,920 cubic meters of water per day with an expected load of 1,140 tons of BOD per day. The volume of treated water represents 2.26 percent of the water withdrawn for consumptive use and 41.1 percent of the total water destined for domestic use. The volume of municipal wastewater treated in 1996 represents a total of 48.9 liters per resident per day. It is of fundamental importance that wastewater treatment plants be developed in the northern border municipalities, where water availability is very limited and there is a growing demand for water. The need to deal with muncipal wastewater is a reality that cannot be put off. Figure 6.19 shows the distribution of treatment plants in the northern border states. Fig. 6.19. Distribution of wastewater treatment plants in the northern border states (1996) 54
60 Number of plants
Of the 787 treatment plants that existed in 1996, 28.8 percent (227) were located in the northern border states. According to this figure, Baja California (9) and Coahuila (17) had the fewest treatment plants among the border states. It is important to note that 93 of the 227 plants located along the border in that year used facultative lagoons – settling ponds that receive wastewater and rely on natural processes to treat it.
52
51
44
50 40 30 17
20
9
10 0
B.C.
Sonora
Chihuahua
Coahuila
N.León
Tamaulipas
Source:CNA, 1996.
Considering that 41 percent of the wastewater treatment plants along the border are facultative lagoons, we should point out that quality of treatment is very deficient for two reasons: a) in the majority of cases, the lagoons’ treatment capacity has been surpassed by population growth; and b) these are passive lagoons that don’t have mechanisms to promote treatment of wastewater. In addition, this method has another disadvantage – the potential for contaminating aquifers in the areas surrounding the receiving ponds. Thirty-nine (17 percent) of all the treatment plants use different processes to treat wastewater: in Baja California, trickling filters; in Chihuahua and Coahuila, enzymatic reactors; and in Nuevo León, activated sludge. Forty-one percent of the plants (93) use a diverse range of treatment technologies: in Baja California, bio-filters and plastic modules; in Sonora, septic tanks and infiltration ponds; in Chihuahua, bio-discs, flotation with air, chemical treatment, metal precipitation, sedimentation, precipitation with solutions in suspension, filtration with activated carbon, aerated ponds, neutralization and trickling filters; in Coahuila, activated soil and chemical treatment; in Nuevo León, Imhoff tanks, septic tanks, aerated ponds, anaerobic reactors, physio-chemical treatments, physical-chemical-biological treatment; extended aeration, oxidation and clarification of floculants; and in Tamaulipas, activated sludge, Imhoff tanks, and physio-chemical treatments. It is worth pointing out that the majority of the audited plants are run by private industry, especially the ones that use advanced technologies.
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Report on the state of the environment and natural resources on Mexico's northern border
Fig. 6.20. Installed capacity vs. volume treated in the northern border states (1996) Daily volume treated
96.2
73.5
68.9
57.6
111.8
213.4
157.6
300
123.1
271.8
600
1016.8
900
707.7
Installed capacity
1200
274.4
Thousands of m3
Figure 6.20 shows the capacity of treatment plants on the border versus the volume of waste treated in cubic meters per day. In 1996, the capacity of the plants in the border states represented 43.9 percent of the treatment capacity on the national level. While plants on the national level treated 86.6 of their operating capacity, the plants in the border states treat 73.6 percent of their operating capacity.
0 B. C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Source:CNA, 1996.
The operating capacity of treatment plants in Nuevo León represents 55.6 percent of the operating capacity in the border states and treats 52.6 percent of the total amount of waste treated in the border states. The treatment plants in the state of Baja California are the most highly utilized, given that they operate at 99.1 percent of their capacity. Those in Sonora are the most underutilized, operating at 52.4 percent of their capacity. While at the national level, plants treat an average of 37.7 liters of wastewater per resident per day, plants in Nuevo León treat 188.2 liters per resident, and plants in Baja California treat 115.8 liters per resident, that is to say, three to five times the national daily average. Coahuila treats the lowest volume of wastewater per resident, at 25.4 liters per day. Chihuahua treats a volume of water equal to the national average. (See Appendix 5.) Fig. 6.21. Treated wastewater as a percentage of total water withdrawn in the northern border states (1996) 70.9
80
Percentage
During 1996, the entities on the border treated 24 percent of the total volume of water they used. Progress in this area is very significant. Even more significantly, Nuevo León has treated 70.9 percent of the volume of water used during that year. This figure should have an important positive environmental impact on the region. Progress by Baja California is also very important. As of Dec. 31, 1996, Baja California treated 33.9 percent of the water withdrawn for diverse uses.
60 40
33.9
11.5
20 0
B.C.
Sonora
10.4
8.9
6.8
Chihuahua Coahuila
N.León
Tamaulipas
Source: CNA, 1996.
However, considering that a significant percent of wastewater is treated by settling ponds, we should emphasize that the waste treated by industrial plants is only 15 percent of the total volume of water withdrawn. This percentage of treated wastewater would be even more relevant had we considered only domestic and industrial uses of water, but necessary data was unavailable. The four other states, which have infrastructure development underway in this area, treated between 6.8 percent and 11.5 percent of the total volume of water withdrawn.
152
Water
There are 62 wastewater treatment plants in the border municipalities, a figure that represents 27.3 percent of the total number of plants in the border states. Their operating capacity represents 33.5 percent of the total operating capacity of the border states’ plants. The volume of waste that they treat, in cubic meters, represents 30.2 percent of the total volume of treated wastes in the northern border states of Mexico. Fig. 6.22. Municipal wastewater treatment plants in priority one municipalities (1996) 140
64.3
65.7 21.6
0.5
Reynosa
N. Laredo
Matamoros
13.0
P. Negras
1.8 1.8
12.8 13.0
4.3
Acuña
Naco
A. Prieta
Tijuana
Mexicali
0
1.3 0.9
20
Ojinaga
40
51.8
53.6 21.0 16.3
60
5.9
80
117.6
Treated volume
Juárez
100
Installed capacity
65.2 67.6
120
96.3 131.8
Thousands of m3
Figure 6.22 shows the operating capacity of the wastewater treatment plants and the volume of wastewater treated per day in cubic meters in the priority one municipalities. The municipalities of Nogales and San Luis Río Colorado, both in Sonora, and Asensción, Chihuahua did not have treatment plants as of Dec. 31, 1996. Wastewater collected by the sewage system in Nogales, Sonora is treated in Nogales, Arizona, by international agreement.
Source:CNA, 1996.
The operating capacity of the treatment plants in the priority one municipalities represents 27.3 percent of the overall operating capacity in the northern border states. The volume of wastewater treated per day by the priority one municipal plants corresponds to 24.5 percent of the total volume of wastewater treated in the border states. However, we should take into consideration that a great number of these municipal plants are facultative lagoons, that is to say, they have the same problems that we referred to in discussing state-run plants. Three of the 14 priority one municipalities do not have treatment plants. Ciudad Juárez has various private plants that treat very small volumes of waste in relation to the volume of water utilized by the city. Half of these private plants use facultative lagoons. Plants in Mexicali, Tijuana, Acuna, Piedras Negras, and Matamoros are working above their operating capacity.
Water Quality Water quality can be based on levels or concentrations of chemical substances, organic material and/or micro-organisms, all of which should be kept below the maximum levels allowed (quality standards) in order for water to be usable for various purposes. The water quality index (ICA) used in Mexico groups together various indicators that together determine the level of quality of the water. The National Water Commission’s Division of Health and Quality of Water has established 783 points that cover the country’s principal bodies of water and permanently maintain information about the quality of water: 383 monitoring sites in 196 rivers; 224 sites for the monitoring of subterranean aquifers; 74 monitoring sites in 24 reservoirs; 25 in sewers; 24 sites in 13 canals; 20 for the monitoring of coastal zones and others. Figure 6.24 shows water quality in 1994. On the national level, only 7.1 percent of the water samples analyzed were acceptable. 5.1 percent were contaminated, 8.7 were heavily contaminated, and 18 percent were extremely contaminated.
153
Report on the state of the environment and natural resources on Mexico's northern border Table 6.4. Scale of water quality by purpose of use ICA range
State
Use: Potable water
State
Use: Agriculture
Excelent
Excelent
No purification required
No treatment required for irrigation
Acceptable
Acceptable
Requires some purification
Minor treatment required for crops that need high-quality water
Slightly contaminated
Slightly contaminated
Consumption questionable without purification
May be used for most crops
50
Contaminated
Contaminated
Purification is essential
Treatment required for most crops
40
Heavily contaminated
Heavily contaminated
Of doubtful utility for consumption
Only for very hardy crops (grasses)
Extremely contaminated
Extremely contaminated
Unacceptable for consumption
Unacceptable for irrigation
Fig. 6.24. Water quality index by CNA region (1994)
39.5
39.5 7.4 7.4
16.3
17.2 0
20
8.7
Water Quality Indicators for the Border XXI Program
7.1 7.1
40
9.8
60
67.5
77.6
80
6.5
100
Slightly contaminated Heavily contaminated
6.2
Acceptable Contaminated Excessively contaminated
1.7
In Figure 6.24 we can see that the northeast region, where 39.5 percent of water samples were acceptable, has the best water quality. The northwest was the region with the most contaminated water.
0 3.5
30 20
18.0
70
59.1
80
Percentage
90
0 Mexico
Northwest
North
Northeast
The Border XXI water working Source: CNA, 1994 group focuses its efforts on binational priorities such as the development of environmental infrastructure, prevention of contamination, watershed planning, water quality monitoring, capacity-building, environmental education and public participation. Water quality indicators measure progress toward abating contamination by the development of required infrastructure for the storage of potable water, sewage, and the improvement of surface and subterranean water quality. It also provides information about the sustainability of water resources in the border zone. The availability of information determines, in great measure, the selection of indicators.
Development of environmental infrastructure projects: Status Indicators •
Percentage of the population with access to potable water.
Indicators of government response • • •
154
Percentage of the population connected to a sewage system. Percentage of wastewater collected for treatment Percentage of total volume of potable water disinfected before distribution.
Water
Quality of Surface and Groundwater Status indicators: • •
Quality of cross border surface water (chlorides, specific conductivity, hardness, phosphates, fats and oil, nitrates, NH3 and NH4, turbidity, fecal coliform, dissolved oxygen, total dissolved solids, and active substances of methylene blue trihydrate. (detergents). Quality of trans-border subterranean water. (same indicators as for surface water).
We present, for the consideration of readers of this document, a list of indicators that could be used to evaluate in a more holistic manner the availability, the status, the usage and the quality of water on the border. Of course, for these indicators to be used, they would have to be accepted and put in practice in a systematic way by the border municipal governments. •
Total availability of water per year: Surface water: Dams (thousands of cubic meters per year) Rivers (thousands of cubic meters per year) Lakes and ponds (thousands of cubic meters per year) Springs (thousands of cubic meters per year) Groundwater (thousands of cubic meters per year)
• • •
Total withdrawal of water in cubic meters per day Total availability of water per resident, in cubic meters per day. Quantity of water withdrawn according to storage sources (surface and deep water) in cubic meters per day Cubic meters per day of water withdrawn per resident. Total percentage of water withdrawn in relation to total amount of water available
• • •
Cubic meters of water distributed to different consumptive uses: Agricultural (cubic meters per hectare per day) Domestic (cubic meters per resident per day) Industrial (cubic meters per business per day) Commercial (cubic meter per day and per established business)
•
Percentage distribution of different uses of consumptive water
•
Number of water service connections Number of household connections Number of industrial connections Number of commercial connections
155
Report on the state of the environment and natural resources on Mexico's northern border
• • • • • • •
Percentage of potable water in relation to the total amount of water destined for consumptive use. Available quantity of potable water (liters per resident per day) Volume of disinfected potable water in relation to the total amount of water destined for domestic use (liters per resident per day). Percentage of potable water in relation to the total amount Average number of household service connections installed on a property per household. Percentage of the population with piped-in water on their property. Average number of industrial water service connections per industry Average number of commercial service connections per business
•
Percentage of metered water service connections. Percentage of domestic connections with meters Percentage of industrial connections with meters Percentage of commercial connections with meters
•
Water rates per cubic meter Domestic water Industrial water Commercial water Agricultural water
•
Cost per cubic meter Domestic water Industrial water Commercial water Agricultural water
•
Percentage of water billed Domestic water Industrial water Commercial water Agricultural water
•
Percentage of water accounts with two or months of bills past due Household water Industrial water Commercial water Agricultural water
• • • • • •
Percentage of households connected to the public sewer system. Number of wastewater treatment plants. Percentage of rudimentary wastewater treatment plants Operating capacity of wastewater treatment plants per day. Volume of wastewater treated per day Percentage of volume of wastewater treated in relation to the total amount of water withdrawn for domestic, industrial and commercial use. Biological Demand of Oxygen (BOD) in tons per day.
•
Index of Water Surface and Groundwater Quality.
156
Water
Executive Summary Both surface water and groundwater in the border region are generally scarce. Annual precipitation in the region is 71 percent lower, on average, than in Mexico overall. While a resident of the state of Chiapas has at his or her disposal 46.6 cubic meters of water per day (17,000 cubic meters of water per year), a person living in Baja California has only 274 liters per day (100 cubic meters per year), that is to say only 0.6 percent of the water available to the Chiapas resident. In 1996, per capita water withdrawal in the country was 6.37 times higher than in the border region. This data clearly shows the poor availability of this precious liquid in the border region. In 1996, 12 percent of the population of the border zone (694,151 people) did not have access to potable water. This population lives predominantly in marginal communities of the urban centers and in rural areas. The majority of municipalities in the border zone, 56 percent, get their water exclusively from deep wells. As a consequence, there is excessive exploitation of subterranean aquifers, a fact that has repercussions for the diminishing supply of water, the increasing costs of pumping, sinking wells and desalinizing water. The total volume of water withdrawn per day depends on the concentration of population and industrial and agricultural development for each of the municipalities analyzed in this report. Priority one municipalities extract 72.6 percent of all water withdrawn on the border. Together these municipalities account for 76.8 percent of the population of the border region, 76.2 percent of the maquiladora licenses, and 65.1 percent of the maquiladora jobs nationwide. In 1996, the three most heavily populated border cities, Tijuana and Mexicali in Baja California and Juárez in Chihuahua, withdrew the greatest volumes of water in the border zone. In that year those three cities withdrew more than 50 percent of the total volume of water withdrawn by the priority one cities. Mexicali also has intense agricultural activity. The fact that 88.1 percent of homes in the priority one cities have water service connections does not necessarily mean that they all had access to potable water. There are some municipalities that only have the infrastructure to provide water two or three times a week even though they have a sanitary water supply system. Although infrastructure for metering the consumption of water has been developed in 69 percent of water systems, only 66 percent of water users in these systems are subject to some kind of charges for water. This is due to the fact that some meters don’t work and because there are administrative deficiencies in the billing system (lack of infrastructure for keeping track of consumers and billing). For the municipalities for which we were able to obtain information, we found that the agencies that administer water operate at a deficit, 135
Report on the state of the environment and natural resources on Mexico's northern border
even when we consider only the established water rates and the cost per cubic meter of water provided. When the significant delays in billing are added, the deficits are even greater. The administration of water, the lack of resources available to provide infrastructure, the costs of operation, and pricing policies are complex matters with social repercussions that directly affect the quality of services provided and prevent the agencies that operate and administer water from being self-sufficient and sustainable. These circumstances also facilitate the irresponsible use of a vital resource in a region characterized by its scarcity. In 1994, the Río Bravo/Río San Juan river basin had a discharge of BOD (biochemical oxygen demand) of 379.8 tons per day, of which 51 percent was municipal discharge (195 tons per day) and 49 percent was industrial discharge (185 tons per day) This is particularly important because the more than 1.5 million people who live in the border municipalities of the state of Tamaulipas depend on water from this river. Wastewater treatment systems in 11 of the priority one municipalities account for 27.3 percent of the wastewater treatment capacity on the northern border. At the same time, these plants treat 24.5 percent of the overall volume of water treated in the border states. Several of the plants were built by the private sector. However, we should consider that 80 percent of the volume of treated water is treated in only three cities (Tijuana, Mexicali and Nuevo Laredo). It is also worth considering that six of these 11 municipalities treat a considerable quantity of wastewater in relation to the overall amount of water used. (between 25 percent and 84 percent).
Water Water is a vital resource for the health and life of people, as well as for wildlife. It is economically and socially essential. As population has grown and industry has developed, the demand for water has also grown, but the amount of available water has not changed. This has caused the management of water to become complex and conflictive, a situation further aggravated by natural phenomena, such as drought.1 This situation is even more extreme along the northern border of Mexico, where water is generally less available than in the rest of the country. In various sub-regions of the border area, such as arid and semi-arid zones, the situation is even more extreme.
1
Fig. 6.1. Availability of water (1997)
1200 800 172.6 400 0 Surface water
Source: CNA, 1997.
National Commission on Water. Hydraulics Program 1995-2000.
136
1473.7
1301.1
1600 Millions of m3 /day
The northern border reflects the distribution of population in the country overall. Ninety-two percent of the overall population of the 79 border municipalities is concentrated in 25 urban centers, 16 of which are located directly on the border with the United States. The rest of the population, 8 percent, resides in 15,127 localities. The fact that people are dispersed in rural areas creates water storage problems. As of December 31, 1996, 694,151
Groundwater
All water
Water
people in the municipalities studied by this report lived without access to potable water (see annex 5).2 That statistic corresponds to 12 percent of the overall population for that year. Most people without potable water lived in marginal areas of the largest cities or in rural areas. Fresh water comes from surface bodies (lakes, ponds, rivers and dams) and subsurface aquifers. The latter are created by natural, renewable recharges or infiltration of irrigation water. The temporary nature and scarcity of rain, along with run-off on the northern border do not generally allow the supply of water to meet the demand, and for that reason water from the subsoil must be withdrawn. According to estimates by the National Water Commission, the volume of surface water available in 1997 was 1,301.1 million cubic meters per day. For 1994, the annual recharge of groundwater was on the order of 172.6 million cubic meters per day.
Average Recharge per Day of Subterranean Aquifers
Millions of m3 per day
Figure 6.2 shows the volume of Fig. 6.2. Average daily recharge of aquifers (1994) recharge of groundwater (daily 172.6 average for 1994) as estimated 200 by the National Water Commission. As we can see, 61.9 160 106.85 percent of the total recharge is 120 65.75 available water and of that 61.5 80 percent is withdrawn. Of the 65.8 million cubic meters of ground40 water withdrawn daily nationwide, 0 1.6 percent is used by the border Annual recharge Annual extraction Available water municipalities. However, if we consider only the 269 aquifers of Source: CNA, 1996. the three hydrologic regions of the northern part of the country (northeast, north and northwest) which are distributed over 14 states, then 9.6 percent of water used from these aquifers is used by the border municipalities. In 1994, the 269 aforementioned aquifers represented3 only 18.5 percent of the annual recharge of the country. Almost of all this available water, 98.6 percent, was withdrawn. Regarding the use of groundwater, it is important to mention that in many cases aquifers are overexploited, with resulting increases in the costs of pumping, and other problems such as sinkholes and the need to desalinate water. As of 1995, 80 of the 459 known aquifers had problems of overexploitation, that is to say more than 20 percent were overexploited and of those, 57 (71.3 percent) were in the northern part of the country. In this sense, almost half the average volume per day of water withdrawn by these cities comes from the ground. Of the 79 municipalities included in this report, 44 (55.7 percent) rely exclusively on deep wells. On the other hand, 65.2 percent of the total recharge of all the aquifers in the country is found in the southeastern part of the country (42.0 million cubic meters per day). The average rainfall for the country is 777 mm per year, or 4,169.9 cubic meters per day. Although the average precipitation for the border area is estimated at 225 mm/year, we 2 3
“Access to water” refers to piped-in water at the home-site. . National Commission on Water, 1996, in “Federal Executive Power, Hydrologic Program, 1995-2000, Mexico.”
137
Report on the state of the environment and natural resources on Mexico's northern border
should emphasize that in a large part of the area the annual rate fluctuates between 50 and 150 mm/ year. That number is equivalent to 193.76 cubic meters per day. It is worth mentioning that in spite of the fact that the border zone occupies 16 percent of the national territory, only 4.6 percent of the overall precipitation falls within the region. It is important to consider not only the total quantity of water that the country receives annually in the form of rain, but also how the rainfall is distributed over the year and over consecutive years, as well as terrain conditions and characteristics by latitude. For example, a person living in Chiapas has at his or her disposal 46.6 cubic meters of water per day (17,000 cubic meters per year) while a resident of Baja California has only 274 liters per day (100 cubic meters per year) or only 0.6 percent of water available to the resident of Chiapas.
Withdrawal and Uses of Water
Percentage
Figure 6.3 presents the Fig. 6.3. Consumptive uses of water in Mexico (1995) 4 withdrawal and uses of water in Mexico during 1995. In it we 83.3 100 present only data referring to 80 consumptive use5 since these statistics are the ones that directly 60 impact the availability of water. 40 The total volume of water 11.6 3.4 1.7 withdrawn in Mexico in 1995 for 20 consumptive and non0 consumptive uses was 5.61 cubic Aquaculture Agriculture Domestic Industrial meters per resident per day. If we consider only the consumptive Source: CNA, 1996. uses (agriculture, domestic use, industry and aqua-culture) the total volume for the same year was 2.21 cubic meters per resident, per day. Of the total volume of water withdrawn for consumptive use, 83.3 percent (167.67 million cubic meters per day) was used for agriculture; 11.6 percent (23.3 million cubic meters per day) was for domestic use; 3.4 percent was used by industry and 1.7 percent for intensive aquaculture. It’s important to point out that the amount of water for agriculture was 7.2 times that used for domestic purposes. Of the total volume of water withdrawn, 249.2 liters/person/day were available for domestic use, versus an average of 1.84 cubic meters per day for agriculture. Water coming from subterranean aquifers has diverse consumptive uses: agricultural, domestic, commercial and industrial. It is often the case that water used by urban centers (domestic, commercial and industrial) is secondarily used for irrigating agriculture, even though it has not been sufficiently treated. The major use of surface water is agriculture and, in the cities that depend on surface water, urban uses. It is important to mention that surface water, after having been used by cities, is often reused to irrigate fields and even as potable water in other locations in the basin below the Río Bravo (Rio Grande). For example, all of the cities bordering this river, from Ojinaga, Chihuahua to Matamoros, Tamaulipas receive 4 5
Total withdrawal: includes the withdrawal of surface and groundwater Consumptive use: impacts the availability of water because of the water used, only part of it is returned. Non-consumptive use: The total amount of water used is returned (generation of electric energy).
138
Water
all or part of their supply of water from this river. In the state of Baja California there is a great dependence on water from the Colorado River. In order to reach Tijuana, that water has to be pumped over the La Rumorosa mountain range at an altitude of 1,100 meters above sea level. After conquering this obstacle, the waters of the Colorado are stored in the El Carrizo reservoir and are pumped across the 125.47 kilometer-long Rio Colorado-Tijuana aqueduct. Moving the water requires six pumping stations. The aqueduct has a capacity of 4 cubic meters per second. Fig. 6.4. Total volume of water withdrawn in the northern border states of Mexico (1996) 1068.5
1200 1000
Thousands of m3
Figure 6.4 shows the total volume of water withdrawn for consumptive uses in the northern border of Mexico during 1996. A total of 5,608,857 cubic meters per day were withdrawn, which is the equivalent of 347 liters per resident per day. The total withdrawal of water per resident in the northern border was less than one-sixth the national average. This clearly shows the poor availability of this precious liquid in the border states.
1070.4
998.7 844.1
802.8
824.2
800 600 400 200 0 B.C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Source: INEGI, 1997.
The states that withdraw the most water per year are Sonora and Chihuahua. The volume of water withdrawn by these two states accounts for 38.2 percent of the total water withdrawn in 1996 in the northern border of the country. Baja California consumes the least amount, accounting for 14.3 percent of the total volume of water withdrawn. However, as we shall see in the next graph (6.5), the panorama appears different when we consider the average amount of water used per resident per day. Fig. 6.5. Average per capita daily withdrawal of water. Northern border states of Mexico (1996)
0.2
0.311
0.266
0.373
0.3
0.342
0.4
0.362
0.484
0.5 Cubic meters
Sonora is the border state with the highest volume of water withdrawn per resident per day, with 484 liters. Next is Coahuila with 373 liters per day, and following that, Chihuahua, with 362 liters per day. Nuevo Leon has the lowest water usage per resident with only 266 liters per day. While the amount of water withdrawn for consumptive uses in Sonora is less than one-fourth the national average, in Nuevo Leon it is less than one-eighth the national average.
0.1 0
B.C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Projected population in 1996, based on the average annual growth rate from 1990 to 1995. Source: INEGI, 1995; INEGI, 1997.
The water supply in the northern border region comes from 2,318 deep wells, 122 springs and 805 other sources, including direct taps into the hydraulic network, dams, aqueducts and surface water infiltration galleries in Baja California. In Sonora sources include surface water infiltration galleries, seeps and hand-dug wells; in Chihuahua they include rivers, dams, surface water infiltration 139
Report on the state of the environment and natural resources on Mexico's northern border
galleries and mines; in Coahuila, rivers and surface water infiltration galleries; in Nuevo Leon, rivers, dams, surface water infiltration galleries and taps into the aqueduct; and in Tamaulipas, river, dams and surface water infiltration galleries. Of the total volume of water withdrawn by the border states, 58.6 percent comes from deep wells, 1.5 percent comes from springs, and 41.7 percent comes from other surface sources. Fig. 6.6. Sources of water in the northern border states (1996) Springs
Others 88.8
Deep wells
Coahuila
Nuevo León
8.8 2.4
1.3
19.6 1.3
Chihuahua
30
79.1
Sonora
1.1
Baja California
2.9
0.7
0
0.1
40 20
68.7
96.0 23.7
60
75.6
61.1
80 38.8
Percentage
100
Tamaulipas
Source: INEGI, 1997.
Figure 6.6 shows the different sources of water in each of the border states. As can be seen, Baja California predominantly obtains water from sources other than deep wells or springs, the states of Sonora, Chihuahua and Coahuila rely predominantly on groundwater (deep wells), and Nuevo Leon and Tamaulipas rely predominantly on rivers and dams. While more than 96 percent of the water used by Chihuahua comes from deep wells, this source only represents 8 percent of the water supply for Tamaulipas.
The Río Bravo (Rio Grande) Basin The Río Bravo basin is very important to the border zone. Given that the basin covers an area of 226,275 square kilometers in five states (Chihuahua, Coahuila, Nuevo Leon, Tamaulipas and Durango), an area which is home to approximately 9 million people, what happens to the river basin has a direct impact on the communities that live in the lower part, principally in the border cities in state of Tamaulipas, where more than 1.5 million people depend on water from this river. Furthermore, 80 percent of the surface water used for agriculture comes from the river. Until 1996, three urban centers in Tamaulipas (Gustavo Ordaz, Reynosa and Matamoros) were supplied with water from the irrigation canals, which were in turn supplied with water from the Río Bravo. From 1996 on, these cities began to get water directly from the river, eliminating the use of canals during the seasons when water wasn’t needed for irrigation, and avoiding the consequent loss of water caused by that practice. Field investigations indicate that total volume of water withdrawn in 1998 was around 371,500 cubic meters per day, which represents a withdrawal per resident on the order of 0.33 cubic meters per day.
140
Water
Figure 6.7 shows the total volume of water withdrawn by the border cities, organized by the four categories defined in this report.
Table 6.1. Cities supplied entirely or partially by Rio Grande water (1996) City
Population
Volume withdrawn, 3 m /day
m /capita/día
88,821
26,000
0.293
120,398
87,000
0.723
Cd. Acuña Piedras Negras
3
116.16
Reynosa
N. Laredo
166.68 34.00
88.00
Matamoros
P. Negras
Acuña
Ojinaga
Juárez
Ascensión
4.26
23.74
74.67
S.L. Col.
1.11
Nogales
25.16
A. Prieta
Tijuana
0
Naco
100
80.19
200
128.74
343.82
239.55
300
Mexicali
Thousands of cubic meters
400
As we see here, Ciudad Juárez, Chihuahua, extracts the greatest volume of water (343,820 cubic meters per day). Juárez accounts for 23.9 percent of the population of the priority one cities, and has the highest concentration of maquiladora industry jobs on the national level (see Appendix 3). Mexicali also stands out because its population is only 69.7 percent the size of the Tijuana’s, yet in
306.36
Thousands of cubic meters
The total volume of water Nuevo Laredo 288,995 128,727 0.445 withdrawn per day in each of Nva. Cd. Guerrero 3,918 1,260 0.322 the categories reflects the Cd. Mier 6,275 1,841 0.274 population, industrial develCd. Miguel Alemán 22,581 6,876 0.304 opment and agricultural development of each of the G. Díaz. Ordaz 15,327 2,950 0.192 categories. For example, Río Bravo 101,736 25,583 0.251 72.6 percent of the daily Reynosa 350,023 114,747 0.328 volume of water withdrawn in Matamoros 377,915 166,072 0.439 the border zone is withdrawn by the 14 priority one Total 1,375,989 561,056 0.408 municipalities, which togeSource: Chávez, O.,1997. ther account for 76.8 percent of the population of the Fig. 6.7. Total water withdrawal in border municipalities (1996) region. When analyzing the 2000 140 average total of water withdrawn Volume extracted per municipality per day per municipality, what 120 1600 stands out that while the priority Average volume extracted per day 100 one municipalities withdrawn 1200 80 116,602.2 cubic meters per day, each of the priority four cities 60 800 withdrew, on average, only 40 3,151.4 cubic meters per day, 400 20 that is, only 2.7 percent of the 0 0 average withdrawn by the priority Priority 1 Priority 2 Priority 3 Priority 4 one cities. The 39 priority four municipalities account for only Source: INEGI, 1997. 8.4 percent of the total population of the border zone. Figure 6.8 shows the total amount of water withdrawn per day in the priority one municipalities. The information refers to water used Fig. 6.8. Total water withdrawn, priority one municipalities (1996) by residents of the municipal seat.
Source: INEGI, 1997.
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Report on the state of the environment and natural resources on Mexico's northern border
1996 it withdrew 27.9 percent more water than Tijuana. There are two fundamental reasons why: there is less water available in Tijuana, and there is a greater level of agricultural activity in Mexicali. Naco and Ascención extract the least amount of water among the priority one municipalities, due to the lack of water, low population, and high proportions of people living in a rural environment. Figure 6.9 shows the total average withdrawal of water per resident per day of people living in the municipal seat. The data does not necessarily show the amount consumed per resident.
0.42
0.32
Reynosa
N. Laredo
0.42
0.71
Matamoros
P. Negras
Acuña
0.30
Ojinaga
Juárez
0.20
Ascensión
S.L.R. Col.
Nogales
0.35
0.52
0.55
0.22
Naco
0.21
0.35
A. Prieta
0.41
Tijuana
Mexicali
Cubic meters per day
1.01
The average amount of water Fig. 6.9. Per capita withdrawal, priority one municipalities (1996) withdrawn per resident in the 1.2 priority one municipalities in 1996 1.0 was 349 liters per day. In this 0.8 graph we see that Ojinaga withdrawn 2.9 times more than 0.6 the median for the municipalities 0.4 of this priority and 5.1 times more 0.2 water than Ascensión. Even so, Ojinaga used on average less 0 than half (45.8 percent) of the water per resident used on the national level. After Ojinaga, Piedras Negras withdrew the Projected population in 1996, based on the average annual growth rate most water per resident – 705 from 1990 to 1995. liters per resident per day. The Source: INEGI, 1995; INEGI, 1997. large border cities that used the least amount of water were, from least to most, Tijuana, Baja California with 213 liters per resident per day; Juárez, Chihuahua, with 306 liters per resident per day; and Matamoros, Tamaulipas, with 320 liters per resident per day. Tijuana’s usage was less than one-tenth the national average; that of Juárez was one-seventh, as was that of Matamoros. Figure 6.10 shows the total daily volume of water utilized by each of the priority two municipalities. We see here that, in 1996, the municipality of Tecate, Baja California used 48.1 percent of the total volume of the 24 municipalities in this category. Although Tecate has about the same population as Caborca, Sonora, the latter used only 18.1 percent of the volume of water used by Tecate. Furthermore, the municipality of Río Bravo,Tamaulipas, which has a population 55.8 the size of the population of Tecate, used 18.9 percent of the water used by Tecate. At the same time, Río Bravo, Tamaulipas, used about the same amount of water as Caborca, even though its population is 23.3 percent of the population of Caborca. Camargo, Tamaulipas, also used about the same amount of water as Caborca, but its population is 54.7 percent greater than Caborca’s.
142
Water
Fig. 6.10. Volume of water withdrawn, priority two municipalities (1996)
148.4
120
28.0 7.1 Río Bravo
1.8
M.Alemán
Mier
Guerrero T.
G.D. Ordaz
1.3
3.7
27.8 4.1 Anáhuac
Camargo
11.0
Ocampo
5.0
3.0
Nava
2.0 Hidalgo
Jiménez
2.0
1.7
Guerrero C.
0.1
P.G. Guerrero
0.7
M. Benavides
Janos
1.1
0.6 Saric
Sta. Cruz
Guadalupe
0.4
14.5
3.1
P. Peñasco
Cananea
Altar
Coborca
Tecate
0
P.E. Calles
40
12.3
26.8
80
2.0
Cubic meters per day
160
Source: INEGI, 1997.
Among the priority two cities, Manuel Benavides, Chihuahua, used the least amount of water at 120 cubic meters per day. Figure 6.11 shows the average volume of water per resident per day used by the priority two cities. Fig. 6.11. Per capita daily water withdrawal by priority two municipalities (1996)
1.80 1.54
2.0
2.18
0.24
0.29
0.31
0.27
G.D. Ordaz
Mier
M. Alemán
Río Bravo
0.33
Guerrero T.
Camargo
0.22
0.46
Ocampo
Anáhuac
0.49
Jiménez
Hidalgo
Guerrero C.
0.18
P.G. Guerrero
0.06
M. Benavides
Janos
0.36
0.66 0.12
Guadalupe
0.26
Saric
0.25
Sta. Cruz
0.37
P. Peñasco
0.30
P.E. Calles
0.4.0
0.41
Cananea
0
Tecate
0.5
Coborca
0.28
1.0
Nava
0.95
1.5
Altar
Cubic meters
2.5
Projected population in 1996, based on the average annual growth rate from 1990 to 1995. Source:
INEGI, 1995; INEGI, 1997.
What stands out here is that Tecate, Baja California, besides using the greatest amount of water among the 79 municipalities studied by this report, has an average water usage per resident very similar to the national median (2.17 cubic meters per resident per day). Among priority two municipalities analyzed by this report, Manuel Benavides, Chihuahua used the least amount of water per resident in 1996, 55 liters per resident per day, an amount which is 36.3 times less than the amount of water used by Tecate and 36.8 times lower than the national average. Janos, Chihuahua, followed with 65 liters per resident. Hidalgo and Guerrero, Coahuila and Camargo, Tamaulipas, with 1.54, 0.95 and 1.80 cubic meters per resident per day respectively, stand out with their high water usage levels, as exceptions to the norm for the other cities in this category, which fluctuated between 115 and 494 liters per resident per day. Undoubtedly these large variations, independent of the
143
Report on the state of the environment and natural resources on Mexico's northern border
consumptive uses in each region, reflect the poor availability of water in the various regions of the border and the occasional excessive use of water in some areas. In the priority three and four municipalities (see Appendix 5), the average water usage per resident was 371 liters per day. While Coyame, Chihuahua used 88 liters per resident per day, Sabinas, Coahuila used 1.23 cubic meters per resident per day and Zaragoza, Coahuila, used 1.08 cubic meters per resident per day. To summarize, of the 79 municipalities analyzed for this report, the three which used the most water per resident were from most to least: Tecate, Baja California, Camargo, Tamaulipas and Guererro, Coahuila. All three are priority two cities. On the other hand, the three cities which used the least amount of water are, from least to most, Manuel Benavides, Janos and Coyame. All three are in Chihuahua. Just over one-third of the deep wells located in the northern border states are within municipalities and 45.1 percent of these are located in the 14 priority one municipalities (352 of the 781). Just over one-fifth of the wells within municipalities are in priority two municipalities, and the remaining 34 percent are in category three and four municipalities.
143
92.31
163
352
Number of wells
Thousands of m3 per day
Figure 6.12 shows the amount of Fig. 6.12. Groundwater withdrawal in border municipalities (1996) groundwater withdrawn by the 500 600 561.53 border municipalities in 1996. 500 Wells 400 Over half (52.2 percent) of the m3 per day 400 300 groundwater was withdrawn by 300 priority one municipalities. This 253.60 200 168.79 200 statistic coincides with the 123 100 concentration of population in 100 these cities. We should remem0 0 ber that the priority one cities Priority 1 Priority 2 Priority 3 Priority 4 have 76.8 percent of the Projected population in 1996, based on the average annual population of the municipal areas growth rate from 1990 to 1995. studied. Priority two municipal Fuente: INEGI, 1995; INEGI, 1997. areas accounted for 23.6 percent of the groundwater withdrawn; priority three municipalities accounted for 8.6 percent, and priority four municipalities accounted for 15.6 percent. In the priority one municipalities, deep wells withdrew on average 1,595.3 cubic meters per day. In the priority two municipal areas, the average was 1.555.8 cubic meters per day; the figures were 1,180.3 cubic meters per day for priority four and 750.5 cubic meters per day for priority three. Those figures correspond to 47 percent of the water withdrawn by priority two cities, 48.2 percent of the water withdrawn by the priority four cities and 63.6 percent of the water withdrawn by the priority three cities. These figures were presented by the National Institute of Statistics, Geography and Information (INEGI) in its annual report on the border states for 1997; however the numbers presumably refer to urban uses of water, since field work shows they significantly underestimate the total volume of water withdrawn.
Water for Domestic Use As we have already mentioned, 11.6 percent of the total water withdrawn in Mexico in 1996 was dedicated to domestic use. This percentage represents an average of 23.288 million cubic meters per day or 249.38 liters per resident per day. According to the National Water
144
Water
Commission,6 15 million Mexicans did not have access to potable water. Of that number, 694,151 lived in the municipalities of the northern border region. In addition, 33.2 percent of the total population lacks sewage systems. The available infrastructure has the capacity to disinfect 95 percent of the water administered to the population for domestic use, and 25.9 percent of this water passes through some processing to make it potable in one of the 356 water processing plants across the country. However, practically all of the bodies of water in the country are contaminated.7 In addition, the safety of water used for domestic purposes is affected by the social, demographic, educational and economic factors detailed in chapter three of this report, such as poverty, the low level of education, social atomization, inadequate hygiene and nutrition, rapid growth of metropolitan areas (population and industry), lack of infrastructure, lack of access to sewer systems, the contamination of aquifers and surface sources of water, as well as problems of access to availability of water. All of these are factors together explain why intestinal infections and their complications are the primary cause of illness in the border area and the fourth cause of death in children under four. Eight percent (2,256) of all deaths in the border area municipalities are due to infectious disease. Of these, 78.6 percent occur in the category one municipalities (see Appendix 4). With respect to infrastructure, as was described above, 12 percent of the total population living along the border zone does not have access to piped-in water, 46.3 percent does not have sewer lines connected to the public system, and almost 50 percent of the population lives in overcrowded conditions. In absolute numbers, approximately 60 percent of this population lives in marginal urban conditions in the 11 large cities located in the northern border region (cities with populations greater than 100,000). The great majority of these cities – 10 of the 11 – are priority one municipalities (see Appendix 1). Inventory of Potable Water Treatment Plants in the Northern Border States of Mexico Fig. 6.13. Water treatment plants in the northern border states (1995) 848.02
30
259.20
10 0
Sonora
3
3
46.657 B.C.
1000 800 600 400
22
20
512.76
450.14
86.40
Chihuahua Coahuila
11
40
42
Number of plants Installed capacity
19
Number of plants
50
N. León
Thousands of m3
In 1995, 287 (76.3 percent) of the 356 water treatment plants located in Mexico were operating. These operating plants had the capacity to treat 6,619,752 cubic meters of water per day, a figure that corresponds to 28.4 percent of all the water destined for domestic use. Figure 6.13 shows the location of water treatment plants by border state and their capacity in cubic meters per day.
200 0 Tamaulipas
Source: CNA, 1996.
Of the 287 plants that were operating in 1996, 100 were located in border states (34.8 percent). During 1995, these 100 plants processed 2.2 million cubic meters of water per day – one-third of all water treated on the national level. Tamaulipas processed 38.5 percent; Nuevo León, 23.3 percent; Baja California, 20.4 percent; and Sonora 11.8 percent, while the states of Coahuila and Chihuahua together processed only 6 percent. It is important to point out that only surface water destined for human consumption was treated; processing is not needed for groundwater. The large dependency on surface water, above all in the border zone, is 6 7
National Water Commission, 1996 Hydraulic Program, 1995-2000. Mexico. INEGI and SEMARNAP, 1997. Estadísticas del Medio Ambiente. México.
145
Report on the state of the environment and natural resources on Mexico's northern border
reflected in the high volume of water treated in the state of Tamaulipas. Another fact that may be related to this is that during 1996, the states of Nuevo León and Tamaulipas had lower general mortality and infant mortality rates from gastrointestinal illnesses than the rest of the border states (see Appendix 4).
Liters per resident
Figure 6.14 shows the volume of Fig. 6.14. Volumen de agua desinfectada, litros por día por habitante en estados de la frontera norte de México (1996) water disinfected per resident during 1996 in each of the 500 403 376 northern border states. In that 400 308 year in the country overall, 92.7 274 243 238 300 percent of water destined for domestic use (21.6 million cubic 200 meters per day) was disinfected, 100 most often by chlorination. Over one-fifth (21.6 percent) of the 0 B.C. Sonora Chihuahua Coahuila N. León Tamaulipas total volume was disinfected in the border states. Chihuahua Fuente: CNA, 1996. disinfected the largest volume of water destined for domestic use among the border states: 1.13 million cubic meters per day, or 403 liters per resident per day. Potable Water Service Connections As of Dec. 31, 1996, the northern border states had introduced a total of 3.4 million water service connections, of which 95 percent (3.2 million) were domestic. In this same year, 4.8 percent of the service connections were commercial and 0.3 percent were industrial. Figure 6.15 shows the distribution of domestic service connections in the border states. Nuevo León has the highest number, with 22.7 percent of the total. According to the figures, in Baja California, 93 percent of the households have service connections, making it the state with the greatest number of houses connected to this important public network. On the other hand, Tamaulipas had the lowest coverage in 1996, with 86 percent of households connected. Figure 6.16 shows the number of household service connections in each of the priority one municipalities and the coverage that represents in each.
800 0.93
0.92
593.01
600 493.22
No. of domestic connections Connections per household
448.27
400
0.94
730.29
0.92 0.90
523.30
0.9
432.03 0.88
0.87
0.86
0.87
0.86
200 0.84 0
0.82 B.C.
Source: INEGI, 1997.
146
Sonora
Chihuahua
Coahuila
N. León
Tamaulipas
No. connections per household
Thousands of domestic connections
Fig. 6.15. Domestic connections to public potable water systems in the northern border states (1996)
Water
Fig. 6.16. Domestic water connections in priority one municipalities (1996) 500
0.82
0.88
0.8 0.6
72.88
0.77
55.20
0.85
24.24
16.80
5.94
206.35 4.80
0.4 0.2
Reynosa
N. Laredo
Matamoros
P. Negras
0 Ojinaga
Ascensión
33.83 S.L.R. Col.
22.90 Nogales
11.98 A. Prieta
Tijuana
0 Mexicali
0.84
0.71
249.03
170.61
200
1
1.00
Acuña
0.64
0.82
Juárez
300
100
1.00 1.00
0.81
No. connections per household
69.17
No. domestic connections
0.99
Naco 1.40
400
1.2 0.98
Fuente: INEGI, 1997.
As of Dec. 31, 1996, 76.7 percent of the potable water domestic service connections in the 79 municipalites included in this report were located in the 14 priority two cities. San Luis Río Colorado, Sonora; Ascensión and Ojinaga, Chihuahua; Tijuana and Mexicali, Baja California, had practically all of their housing units hooked up to the potable water system, according to the annual statistics from the respective states. However, a field investigation showed that San Luis Río Colorado had the best coverage, with 99 percent of its housing units in the municipal seat hooked up in 1997. It is important to clarify that this information comes from the various agencies which provide water service, which, in the majority of cases, only consider housing units in the municipal seat, and possibly some semi-rural areas. In the following municipalities, 15 percent or more of housing units were not connected to potable water as of 1996: Naco (64 percent), Nogales (71 percent), and Agua Prieta (81 percent), Sonora; Matamoros (77 percent) and Nuevo Laredo (82 percent), Tamaulipas; Ciudad Juárez, Chihuahua (82 percent); and Acuña, Coahuila (84 percent). Table 6.2 Growth in the number of domestic connections (1996-1997) Municipality
Tijuana Tecate S.L.R. Colorado Nogales Cd. Juárez Cd. Acuña Piedras Negras Reynosa Matamoros Total
Domestic connections 1996 * 249,026 13,204 33,877 22,892 206,349 16,790 24,238 72,875 69,169 708,420
Domestic connections 1997 ** 267,612 14,484 40,500 23,500 228,275 18,612 24,910 98,420 69,650 785,963
Growth in number of domestic connections 7.46% 9.69% 19.55% 2.65% 10.63% 10.85% 2.77% 35.05% 0.70% 10.94%
Average annual population growth 6.54% 4.29% 4.09% 4.74% 5.34% 8.97% 3.66% 3.85% 3.97% 4.1%
Source: * INEGI, 1997. ** Field investigation.
These municipalities account for 57.5 percent of the all the domestic water service connections in the 79 municipalities included in this report. In Table 6.2, we see an average increase of 10.9 percent in the available water infrastructure between 1996 and 1997 in the selected municipalities. The most important improvement was in Reynosa, Tamaulipas 147
Report on the state of the environment and natural resources on Mexico's northern border
which, in only one year, saw an increase of 35 percent. Tecate, Baja California, considered within priority two, had an increase of 9.7 percent, which indicates a significant setback in the existing infrastructure. Since there is migration to urban centers, deficits in service continue, despite improvements in infrastructure.
0.81 0.87
0.95
1.00 0.87
1.00 1.00 0.98
1.00 0.85
5.92
4.02
0.4 0.2
2.07
1.22
3.64
1.02
2.10
4.73
5.30 0.15
1.90
0.28
0.40
1.64
2.09
Mier
G.D. Ordaz
Guerrero T.
Camargo
Anáhuac
Ocampo
Jiménez
Hidalgo
Guerrero C
P.G. Guerrero
M. Benavides
Jano
0.39
0.8
0 Guadalupe
0.32
0.45
0.27
1
0.6
0.47 0.46
Saric
P. Peñasco
P.E. Calles
Coborca
Cananea
Altar
0 Tecate
0.63
7.88
5.89
1.05
1.86
5
0.74
Nava
0.68 10.96
13.20
0.74
19.8
0.95
0.89
1.00
0.82
15 10
1.00
1.2
No. connections per household
Río Bravo
0.87
Sta. Cruz
20
No. domestic connections
M. Alemán
25
Connections per household
Thousands of connections
Fig. 6.17. Domestic water connections in priority two municipalities (1996)
Source: INEGI, 1997.
Figure 6.17 shows the distribution of domestic water service connections in the priority two municipalities. Here we see that in 1996, 25 percent of the priority two municipalities had all of their private housing units connected to the potable water system. The municipalities with complete covererage were Puerto Peñasco, Sonora; Hidalgo, Coahuila; Camargo, Guerrero, Mier and Miguel Alemán, Tamaulipas. Field work shows that Guerrero and Mier, Tamaulipas report 85 percent and 95 percent coverage in their municipal seats, respectively. Four municipalities in the state of Coahuila had less than 50 percent of their housing units connected to water: Guerrero, Jimenez, Nava and Ocampo. Of all the category two municipalities, Jiménez, Coahuila had the lowest percentage of housing units connected to potable water, with only 15 percent. Of the priority three and four municipalities, 56.4 percent had all of their housing units connected to domestic water service connections (see Appendix 5). In fact, the municipalities in this category had better coverage than those in the other two categories (94 percent on average). Figure 6.18 shows the percentage of domestic water service connections in the municipal seats that have meters in relation to the percentage of water that is billed in 13 border cities. While the infrastructure for metering water consumption is underdeveloped, the infrastructure for billing water service is even less developed, due to some percentage of meters not working, administrative deficiencies in the billing system, or both. This means that the presence of water meters does not necessarily assure that water usage is being billed to the consumer.
148
Water
Fig. 6.18. Percentage of domestic connections with meters and percentage of service that is billed (1998)
78
80
68
100
93
92
80
75
76 60
75 62
54
60
60 38
40
50
47
46
53
51
48
32
20
5 Camargo
Jiménez,
P. Negras
Acuña
Ojinaga
Juárez
S.L.R. Col.
Tecate
Ensenada
Tijuana
Mexicali
0 0
97
10 Río Bravo
Percentage
100
Percentage billed
Percentage of connections with meters 93
Matamoros
120
Fuente: Chávez O., 1998
For example, in the 13 municipalities for which we were able to obtain information, there are a total of 923,979 service connections (domestic, commercial and industrial). This statistic represents 71.6 percent of the total number of connections in the 79 border municipalities. Of that number, 68.6 percent (633,525) are metered, and 65.6 percent are subject to some type of billing for water service; they are either billed according to the water usage recorded by the meter, according to pre-established rates that don’t take into account actual usage, or in some cases, a rate established by annual average use. In the chart we see that in various municipalities the percentage of connections billed to the user surpasses the percentage of connections with meters. These municipalities include San Luis Río Colorado, Sonora; Ojinaga, Chihuahua; Acuña, Piedras Negras y Jiménez, Coahuila; Camargo, Matamoros; and Río Bravo in Tamaulipas. Table 6.3 shows the rate per cubic meter of water, the cost per cubic meter, the volume of water withdrawn per day, and the percentage of water that is billed. (The prices and costs are in Mexican pesos.) Although the data in the table is not exact, because the volumes of water withdrawn are for 1996, not 1998, and because the percentage of bills refers to the number of accounts and not to the volume of water provided per day, the table does show us the deficits in the water systems, with the exception of San Luis Rio Colorado. The agencies that administer water operate in a limited manner and in some cases at a deficit. Although in some cases there are operating surpluses, they are not enough to cover the costs of maintaining and improving the water system and therefore the systems rely on state and federal subsidies. The administration of water as a resource, the lack of resources to solve infrastructure problems, operating costs, pricing policies, the definition and setting of water rates, besides being complex issues which have social and economic repercussions, Tabla 6.3. Tarifas, costo y porcentaje de cobranza del servicio de agua 3
Municipalities SLR Colorado Juárez, Chih. Acuña, Coah. Piedras Negras Camargo, Tamps. Reynosa, Tamps. Río Bravo, Tamps.
Rate per m 1998 20.00 23.00 20.00 20.00 10.00 20.00 20.00
3
Cost per m servido 1998 15.00 28.00 26.00 40.00 19.00 26.00 22.00
Volume withdrawn, 3 m /day 1996 74,673 343,820 34,000 88,000 27,809 116,158 28,010
Percentage collected 1996 80 62 50 51 97 58 48
Surplus or deficit in peos per day 74,673.00 -4,724,086.80 -544,000.00 -2,622,400.00 -258,623.70 -1,672,675.20 -347,324.00
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Report on the state of the environment and natural resources on Mexico's northern border
directly affect the quality of services provided and limit the institutions the operate and administer water, keeping them from being self-sufficient and sustainable.
Biochemical Demand of Oxygen (BOD) According to the Hydraulic Program for 1995-2000, municipalities generate 20 million cubic meters of wastewater daily, but the sewage systems collect only 75.3 percent of that, that is to say 15.07 million cubic meters per day. The Biochemical Oxygen Demand (BOD) is an indicator of organic contamination (organic material and bacteria) in water. It is estimated that in 1998, the country’s population generated 1.8 million tons of BOD, of which 67.8 percent (1.22 million tons) were collected by sewage systems. Of the amount collected, only 12.3 percent (0.15 tons of BOD) were adequately treated. A study of BOD in contaminated discharges in selected river basins8 determined that in 1994, the Río Bravo/Río San Juan basin had a discharge of BOD of 379.8 tons per day, with 51.3 percent (194.8 tons per day) coming from municipalities and 48.7 percent (185 tons per day) coming from industry. It is important to point out that a percentage of the discharges into this basin are municipal discharges for the metropolitan area of Monterrey. In that same year, 3.8 percent of the total amount of discharges of industrial wastewater into selected river basins was into the Río Bravo/Río San Juan. It is estimated that for the year 2000, the total demand for potable water for domestic use will be 25.7 million cubic meters per day and 1.95 million tons of BOD will be generated. Of that total amount of BOD, 76.4 percent will be captured by sewers. Compared to 1997, there will be a 21.5 percent increase in demand for potable water and the increase in generation of BOD will be 8.3 percent, from 1.8 million tons in 1997 to 1.95 million tons in 2000. Sewage Systems in the Border Municipalities and States As of December 31, 1996, there were 324 sewage systems in the northern border states which serviced 326 of the 41,271 settlements in the region. These figures do not include information from the state of Nuevo León (due to lack of data). Baja California, Sonora, Chihuahua, Coahuila, and Tamaulipas covered 79 percent of their settlements. However, we should consider that 97.6 percent of the 41,271 towns are too small to have a sewage system (less than 500 inhabitants). Taking into consideration the fact that only settled areas with 500 or more residents have sewage systems (991 locations), then only 32.9 percent of settlements have these services. The 14 priority one municipalities have 25 systems. They serviced 24 of the 5,399 settlements that are within the priority one municipalities. Deducting the number of settlements with less than 500 inhabitants (5,270) from the total, we conclude that sewage systems covered 18.6 percent of the 129 settlements with 500 or more residents. The 23 priority two municipalities (not including Anahuac, Nuevo León) have 37 sewage systems that cover 37 of the 3,959 settlements. The systems cover 52.9 percent of settled areas with 500 or more people. We should point out that all medium and large urban centers have sewage systems.
8
National Water Commission, 1996. Diagnosis of Environmental Health Actions on the National Level, Mexico, 1996.
150
Water
Municipal Wastewater Treatment Plants On the national level, the capacity of wastewater treatment plants increased by 3,369,600 cubic meters per day from 1988 to 1996. In 1996, there were 787 municipal wastewater treatment plants in the country, which treated 4,561,920 cubic meters of water per day with an expected load of 1,140 tons of BOD per day. The volume of treated water represents 2.26 percent of the water withdrawn for consumptive use and 41.1 percent of the total water destined for domestic use. The volume of municipal wastewater treated in 1996 represents a total of 48.9 liters per resident per day. It is of fundamental importance that wastewater treatment plants be developed in the northern border municipalities, where water availability is very limited and there is a growing demand for water. The need to deal with muncipal wastewater is a reality that cannot be put off. Figure 6.19 shows the distribution of treatment plants in the northern border states. Fig. 6.19. Distribution of wastewater treatment plants in the northern border states (1996) 54
60 Number of plants
Of the 787 treatment plants that existed in 1996, 28.8 percent (227) were located in the northern border states. According to this figure, Baja California (9) and Coahuila (17) had the fewest treatment plants among the border states. It is important to note that 93 of the 227 plants located along the border in that year used facultative lagoons – settling ponds that receive wastewater and rely on natural processes to treat it.
52
51
44
50 40 30 17
20
9
10 0
B.C.
Sonora
Chihuahua
Coahuila
N.León
Tamaulipas
Source:CNA, 1996.
Considering that 41 percent of the wastewater treatment plants along the border are facultative lagoons, we should point out that quality of treatment is very deficient for two reasons: a) in the majority of cases, the lagoons’ treatment capacity has been surpassed by population growth; and b) these are passive lagoons that don’t have mechanisms to promote treatment of wastewater. In addition, this method has another disadvantage – the potential for contaminating aquifers in the areas surrounding the receiving ponds. Thirty-nine (17 percent) of all the treatment plants use different processes to treat wastewater: in Baja California, trickling filters; in Chihuahua and Coahuila, enzymatic reactors; and in Nuevo León, activated sludge. Forty-one percent of the plants (93) use a diverse range of treatment technologies: in Baja California, bio-filters and plastic modules; in Sonora, septic tanks and infiltration ponds; in Chihuahua, bio-discs, flotation with air, chemical treatment, metal precipitation, sedimentation, precipitation with solutions in suspension, filtration with activated carbon, aerated ponds, neutralization and trickling filters; in Coahuila, activated soil and chemical treatment; in Nuevo León, Imhoff tanks, septic tanks, aerated ponds, anaerobic reactors, physio-chemical treatments, physical-chemical-biological treatment; extended aeration, oxidation and clarification of floculants; and in Tamaulipas, activated sludge, Imhoff tanks, and physio-chemical treatments. It is worth pointing out that the majority of the audited plants are run by private industry, especially the ones that use advanced technologies.
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Report on the state of the environment and natural resources on Mexico's northern border
Fig. 6.20. Installed capacity vs. volume treated in the northern border states (1996) Daily volume treated
96.2
73.5
68.9
57.6
111.8
213.4
157.6
300
123.1
271.8
600
1016.8
900
707.7
Installed capacity
1200
274.4
Thousands of m3
Figure 6.20 shows the capacity of treatment plants on the border versus the volume of waste treated in cubic meters per day. In 1996, the capacity of the plants in the border states represented 43.9 percent of the treatment capacity on the national level. While plants on the national level treated 86.6 of their operating capacity, the plants in the border states treat 73.6 percent of their operating capacity.
0 B. C.
Sonora
Chihuahua Coahuila
N.León
Tamaulipas
Source:CNA, 1996.
The operating capacity of treatment plants in Nuevo León represents 55.6 percent of the operating capacity in the border states and treats 52.6 percent of the total amount of waste treated in the border states. The treatment plants in the state of Baja California are the most highly utilized, given that they operate at 99.1 percent of their capacity. Those in Sonora are the most underutilized, operating at 52.4 percent of their capacity. While at the national level, plants treat an average of 37.7 liters of wastewater per resident per day, plants in Nuevo León treat 188.2 liters per resident, and plants in Baja California treat 115.8 liters per resident, that is to say, three to five times the national daily average. Coahuila treats the lowest volume of wastewater per resident, at 25.4 liters per day. Chihuahua treats a volume of water equal to the national average. (See Appendix 5.) Fig. 6.21. Treated wastewater as a percentage of total water withdrawn in the northern border states (1996) 70.9
80
Percentage
During 1996, the entities on the border treated 24 percent of the total volume of water they used. Progress in this area is very significant. Even more significantly, Nuevo León has treated 70.9 percent of the volume of water used during that year. This figure should have an important positive environmental impact on the region. Progress by Baja California is also very important. As of Dec. 31, 1996, Baja California treated 33.9 percent of the water withdrawn for diverse uses.
60 40
33.9
11.5
20 0
B.C.
Sonora
10.4
8.9
6.8
Chihuahua Coahuila
N.León
Tamaulipas
Source: CNA, 1996.
However, considering that a significant percent of wastewater is treated by settling ponds, we should emphasize that the waste treated by industrial plants is only 15 percent of the total volume of water withdrawn. This percentage of treated wastewater would be even more relevant had we considered only domestic and industrial uses of water, but necessary data was unavailable. The four other states, which have infrastructure development underway in this area, treated between 6.8 percent and 11.5 percent of the total volume of water withdrawn.
152
Water
There are 62 wastewater treatment plants in the border municipalities, a figure that represents 27.3 percent of the total number of plants in the border states. Their operating capacity represents 33.5 percent of the total operating capacity of the border states’ plants. The volume of waste that they treat, in cubic meters, represents 30.2 percent of the total volume of treated wastes in the northern border states of Mexico. Fig. 6.22. Municipal wastewater treatment plants in priority one municipalities (1996) 140
64.3
65.7 21.6
0.5
Reynosa
N. Laredo
Matamoros
13.0
P. Negras
1.8 1.8
12.8 13.0
4.3
Acuña
Naco
A. Prieta
Tijuana
Mexicali
0
1.3 0.9
20
Ojinaga
40
51.8
53.6 21.0 16.3
60
5.9
80
117.6
Treated volume
Juárez
100
Installed capacity
65.2 67.6
120
96.3 131.8
Thousands of m3
Figure 6.22 shows the operating capacity of the wastewater treatment plants and the volume of wastewater treated per day in cubic meters in the priority one municipalities. The municipalities of Nogales and San Luis Río Colorado, both in Sonora, and Asensción, Chihuahua did not have treatment plants as of Dec. 31, 1996. Wastewater collected by the sewage system in Nogales, Sonora is treated in Nogales, Arizona, by international agreement.
Source:CNA, 1996.
The operating capacity of the treatment plants in the priority one municipalities represents 27.3 percent of the overall operating capacity in the northern border states. The volume of wastewater treated per day by the priority one municipal plants corresponds to 24.5 percent of the total volume of wastewater treated in the border states. However, we should take into consideration that a great number of these municipal plants are facultative lagoons, that is to say, they have the same problems that we referred to in discussing state-run plants. Three of the 14 priority one municipalities do not have treatment plants. Ciudad Juárez has various private plants that treat very small volumes of waste in relation to the volume of water utilized by the city. Half of these private plants use facultative lagoons. Plants in Mexicali, Tijuana, Acuna, Piedras Negras, and Matamoros are working above their operating capacity.
Water Quality Water quality can be based on levels or concentrations of chemical substances, organic material and/or micro-organisms, all of which should be kept below the maximum levels allowed (quality standards) in order for water to be usable for various purposes. The water quality index (ICA) used in Mexico groups together various indicators that together determine the level of quality of the water. The National Water Commission’s Division of Health and Quality of Water has established 783 points that cover the country’s principal bodies of water and permanently maintain information about the quality of water: 383 monitoring sites in 196 rivers; 224 sites for the monitoring of subterranean aquifers; 74 monitoring sites in 24 reservoirs; 25 in sewers; 24 sites in 13 canals; 20 for the monitoring of coastal zones and others. Figure 6.24 shows water quality in 1994. On the national level, only 7.1 percent of the water samples analyzed were acceptable. 5.1 percent were contaminated, 8.7 were heavily contaminated, and 18 percent were extremely contaminated.
153
Report on the state of the environment and natural resources on Mexico's northern border Table 6.4. Scale of water quality by purpose of use ICA range
State
Use: Potable water
State
Use: Agriculture
Excelent
Excelent
No purification required
No treatment required for irrigation
Acceptable
Acceptable
Requires some purification
Minor treatment required for crops that need high-quality water
Slightly contaminated
Slightly contaminated
Consumption questionable without purification
May be used for most crops
50
Contaminated
Contaminated
Purification is essential
Treatment required for most crops
40
Heavily contaminated
Heavily contaminated
Of doubtful utility for consumption
Only for very hardy crops (grasses)
Extremely contaminated
Extremely contaminated
Unacceptable for consumption
Unacceptable for irrigation
Fig. 6.24. Water quality index by CNA region (1994)
39.5
39.5 7.4 7.4
16.3
17.2 0
20
8.7
Water Quality Indicators for the Border XXI Program
7.1 7.1
40
9.8
60
67.5
77.6
80
6.5
100
Slightly contaminated Heavily contaminated
6.2
Acceptable Contaminated Excessively contaminated
1.7
In Figure 6.24 we can see that the northeast region, where 39.5 percent of water samples were acceptable, has the best water quality. The northwest was the region with the most contaminated water.
0 3.5
30 20
18.0
70
59.1
80
Percentage
90
0 Mexico
Northwest
North
Northeast
The Border XXI water working Source: CNA, 1994 group focuses its efforts on binational priorities such as the development of environmental infrastructure, prevention of contamination, watershed planning, water quality monitoring, capacity-building, environmental education and public participation. Water quality indicators measure progress toward abating contamination by the development of required infrastructure for the storage of potable water, sewage, and the improvement of surface and subterranean water quality. It also provides information about the sustainability of water resources in the border zone. The availability of information determines, in great measure, the selection of indicators.
Development of environmental infrastructure projects: Status Indicators •
Percentage of the population with access to potable water.
Indicators of government response • • •
154
Percentage of the population connected to a sewage system. Percentage of wastewater collected for treatment Percentage of total volume of potable water disinfected before distribution.
Water
Quality of Surface and Groundwater Status indicators: • •
Quality of cross border surface water (chlorides, specific conductivity, hardness, phosphates, fats and oil, nitrates, NH3 and NH4, turbidity, fecal coliform, dissolved oxygen, total dissolved solids, and active substances of methylene blue trihydrate. (detergents). Quality of trans-border subterranean water. (same indicators as for surface water).
We present, for the consideration of readers of this document, a list of indicators that could be used to evaluate in a more holistic manner the availability, the status, the usage and the quality of water on the border. Of course, for these indicators to be used, they would have to be accepted and put in practice in a systematic way by the border municipal governments. •
Total availability of water per year: Surface water: Dams (thousands of cubic meters per year) Rivers (thousands of cubic meters per year) Lakes and ponds (thousands of cubic meters per year) Springs (thousands of cubic meters per year) Groundwater (thousands of cubic meters per year)
• • •
Total withdrawal of water in cubic meters per day Total availability of water per resident, in cubic meters per day. Quantity of water withdrawn according to storage sources (surface and deep water) in cubic meters per day Cubic meters per day of water withdrawn per resident. Total percentage of water withdrawn in relation to total amount of water available
• • •
Cubic meters of water distributed to different consumptive uses: Agricultural (cubic meters per hectare per day) Domestic (cubic meters per resident per day) Industrial (cubic meters per business per day) Commercial (cubic meter per day and per established business)
•
Percentage distribution of different uses of consumptive water
•
Number of water service connections Number of household connections Number of industrial connections Number of commercial connections
155
Report on the state of the environment and natural resources on Mexico's northern border
• • • • • • •
Percentage of potable water in relation to the total amount of water destined for consumptive use. Available quantity of potable water (liters per resident per day) Volume of disinfected potable water in relation to the total amount of water destined for domestic use (liters per resident per day). Percentage of potable water in relation to the total amount Average number of household service connections installed on a property per household. Percentage of the population with piped-in water on their property. Average number of industrial water service connections per industry Average number of commercial service connections per business
•
Percentage of metered water service connections. Percentage of domestic connections with meters Percentage of industrial connections with meters Percentage of commercial connections with meters
•
Water rates per cubic meter Domestic water Industrial water Commercial water Agricultural water
•
Cost per cubic meter Domestic water Industrial water Commercial water Agricultural water
•
Percentage of water billed Domestic water Industrial water Commercial water Agricultural water
•
Percentage of water accounts with two or months of bills past due Household water Industrial water Commercial water Agricultural water
• • • • • •
Percentage of households connected to the public sewer system. Number of wastewater treatment plants. Percentage of rudimentary wastewater treatment plants Operating capacity of wastewater treatment plants per day. Volume of wastewater treated per day Percentage of volume of wastewater treated in relation to the total amount of water withdrawn for domestic, industrial and commercial use. Biological Demand of Oxygen (BOD) in tons per day.
•
Index of Water Surface and Groundwater Quality.
156
