Water shortages threaten society. - ClassZone
KEY CONCEPT
Water shortages threaten society. Sunshine State STANDARDS SC.D.1.3.1: The student knows how conditions that exist in one system influence the conditions that exist in other systems. SC.D.2.3.1: The student understands that quality of life is relevant to personal experience.
BEFORE, you learned
NOW, you will learn
• Water is treated for drinking • Wastewater is treated and released • Pollutants contaminate the water supply
• How overuse causes water shortages • How water can be conserved • How governments and organizations manage water use
EXPLORE The Value of Fresh Water
Does water cost more than gasoline? PROCEDURE
VOCABULARY drought p. 101 desalination p. 106
1
Find out the current price of a liter of bottled water.
MATERIALS calculator
2 Find out the current price of a gallon
of gasoline. 3 To calculate the price of gasoline in
liters, multiply the price per gallon by 0.26.
WHAT DO YOU THINK? • How do the prices of bottled water and gasoline compare? • What do your results tell you about the value of drinking water?
Water shortages are a global problem. SUPPORTING MAIN IDEAS Support the main idea of global water shortages with details and examples.
Most nations in the deserts of northern Africa and in the Middle East have severe water shortages. These are some of the driest regions on Earth, but their populations require more and more water as cities grow. Water that could be used to grow food is piped instead to the growing cities, where it is needed in homes and factories. So how do people in these regions grow enough food? For the most part, they cannot. There is simply not enough water. Jordan imports, or brings in from other countries, about 91 percent of its grain. Israel imports about 87 percent, and Egypt, once a center of agriculture, imports 40 percent.
100 Unit 1: Earth’s Waters
All over the world, the water supply is dwindling. Populations are growing everywhere, and people must be fed. Farmers draw water from underground aquifers faster than the water can be replaced. Even places that normally get regular rainfall can face water shortages. Drought (drowt) is a long period of abnormally low rainfall. Drought can destroy crops and dry up water supplies. Usually, trees can survive a dry period because their roots reach into the ground for water. However, severe drought can dry out entire forests. Dry trees are more vulnerable to disease, and wildfires are harder to control.
Overuse can cause water shortages. As the world’s population grows, usable fresh water is becoming scarcer in many places. Agriculture uses two-thirds of the world’s available fresh water. Unfortunately, only half of that water reaches the roots of the plants. The other half is lost to evaporation and runoff.
MARYLAND
Overuse of underground water can cause an aquifer to be depleted, or consumed faster than its water is replaced. In most places where crops require irrigation, farmers water their fields with groundwater. India is using twice as much water from its aquifers as can be replaced. In the United States, farmers are taking so much water that they are draining the huge Ogallala Aquifer. The problem is that underground stores of water can take thousands of years to refill. Draining an aquifer can also destroy it. When water is removed, the ground may settle and close up the storage space.
A bridge stands over a dried-out part of a reservoir during a drought in Maryland.
River water is also being overused in many places. So much water is being taken out that many major rivers now run dry for a large part of the year. These rivers include the Ganges River in South Asia, the Indus River in Pakistan, and the Colorado River in the southwestern United States. People in seven western states use water from the Colorado. As cities in these states have grown, the demand for the river water has increased. How has overuse of water affected some rivers?
Chapter 3: Freshwater Resources 101
Fresh water can be conserved. SUPPORTING MAIN IDEAS Record in your notes the important details about water conservation.
Although water shortages are a serious problem, the situation is not entirely hopeless. Conserving can solve a big part of the problem. Conservation is action taken to protect and preserve the natural world. To conserve water means to use less of it. U.S. Household Water Usage Americans use an average of 168 liters per person each day.
toilet flushes 29%
toilet leaks 5% dishwashing 3% bath 9%
washing machine 21%
tap 12% shower 21%
SOURCE: U.S. Environmental Protection Agency
The chart above shows how Americans use water each day. The amount that each American uses on average—168 liters—is higher than in most parts of the world. Note that 5 percent of the amount—more than 8 liters—is wasted by leaking toilets.
These water-catching devices are used to collect and store rainwater in Hawaii.
The Need for Conservation Think about what you already know about the water cycle. When aquifers, lakes, and rivers are depleted—or used up faster than the water in them can be replaced naturally—available fresh water from those water supplies decreases. Because water supplies in many regions are being depleted, conservation is an urgent issue. Much of the western United States is mostly desert, and yet the population in dry parts of the West is growing each year. What will happen if the aquifers and rivers that supply this region with water dry up? The less water that people use today, the more water there will be to use in the future. Water shortages are an increasing problem around the world as the population grows in many regions. About half a billion people in 31 countries—mostly in the Middle East and Africa—currently face water shortages. By 2025, the number of people without enough water will increase five times, to about 2.8 billion people.
102 Unit 1: Earth’s Waters
Conservation Practices People conserve water in three ways. The first way is to use less water. Some cities conserve their supply of water simply by repairing leaks in underground pipes. The second way is to reuse water. Many cities reuse treated wastewater for landscaping. The third method is to recycle water, or use water again for the same purpose.
RESOURCE CENTER CLASSZONE.COM
Learn more about water conservation.
Farmers can conserve water by using drip irrigation instead of spraying water. They can change the grooves in their fields so the water stays in the soil longer. Most industries can use water at least twice before returning it to a river or lake. For example, water used to cool machines can be recycled back through the same system. At home, people can change their plumbing and their habits. Low-flow toilets and showerheads can cut water use in half. People conserve water by turning off the faucet while brushing their teeth, taking shorter showers, and running the dishwasher only when it is full. Leaking pipes and dripping faucets in homes cause huge amounts of water to be wasted. Repair and maintenance of plumbing systems would reduce water use greatly. Check Your Reading
What are the three main ways in which people conserve water?
Water Conservation How much water does a dripping faucet use? 1
Adjust a faucet so that water drips slowly.
2
Set a container under the faucet and collect the dripping water for five minutes.
3
Turn off the faucet. Use the graduated cylinder to measure how much water dripped. Record your results in milliliters.
4
Multiply the amount by 12 to determine how much water would drip in an hour. Then divide that number by 1000 to convert your result to liters.
SKILL FOCUS Measuring
MATERIALS • • • •
water faucet container funnel 100 mL graduated cylinder
TIME 20 minutes
WHAT DO YOU THINK? • How much water would one leaky faucet waste in a day? • In a town with 2000 houses with one leaky faucet in each, how much water would be wasted each day?
CHALLENGE How could you combine your results with those of your classmates to make the results more reliable?
Chapter 3: Freshwater Resources 103
People can balance water needs and uses. People around the world have different views about how water should be used. Americans in the hot Southwest might want water for swimming pools and lawns. Developing countries need water to prevent disease and grow food. In some places, farmers use river water before it can reach others downstream. Some industries want water to make products. As water becomes scarcer, the arguments become more serious. Public officials and experts can help manage water use and enforce fair laws. For example, what happens when a river flows from one state into another or across a national border? In such a situation, people must agree to share the water rights. The Rio Grande flows through two states and then between Texas and Mexico. The water in this river is an international issue. In 1939 a legal agreement was made between the states of Colorado, New Mexico, and Texas, and between the United States and Mexico. It listed how much water each region could take. In the past, water from the Rio Grande was used for farming. However, cities along the river are growing rapidly. All the cities need more water from the Rio Grande, and every year they will need more. The international agreement no longer solves this urgent problem. American and Mexican officials are looking for new solutions.
Much Demand for the Rio Grande Three states and Mexico share the water of the Rio Grande. The Rio Grande begins its flow in Colorado. The agreement states that Colorado must allow a certain amount of water to flow into New Mexico.
By 2050 the population of Ciudad Juárez, Mexico, could be larger than all of New Mexico’s population.
104 Unit 1: Earth’s Waters
New Mexico’s largest city, Albuquerque, continues to expand, increasing demand for Rio Grande water.
New Mexico has dams and reservoirs to store reserves of water.
So much water is used upstream that the riverbed between El Paso and Presidio, Texas, is sometimes dry.
Shortages When there is not enough water, crops will not grow. And when the crops fail to grow, there is not enough food to eat. The Middle East countries that import most of their grain are, in a way, importing water. Billions of tons of water are used to grow the imported grain. International organizations help out countries where drought and floods have destroyed the crops. For example, in 2002 the World Food Programme alerted the world to a serious lack of food in southeast Africa. The United Nations agencies arranged for food aid. The shrinking of Lake Chad has also caused hardship for many Africans. In the future, people may solve some of the problems by sharing water around the world. The governor of Alaska has suggested an undersea pipeline. This line would be between 2200 kilometers (1360 mi) and 3400 kilometers (2100 mi) long. Through this pipe, thousands of liters of fresh water would flow from Alaska to California. Some people have also suggested selling Great Lakes water to Japan. Many people in states and Canadian provinces around the lakes have strongly objected, because they think removing water could damage the lakes. check your reading
Lake Chad
This satellite photograph of Lake Chad in Africa was taken in 1973.
How can Alaska help solve a water shortage in California?
Pollution A recent photograph shows how Where water flows across the boundaries of nations, much the lake has shrunk. pollution can flow across as well. One example of this problem is the Danube River in Europe. This river begins in the Black Forest in Germany. It empties into the Black Sea on the coast of Romania. As it flows through the cities of Vienna, Budapest, and Belgrade, more and more pollution is added to the water. Seventeen countries border either the Danube River or the Black Sea. To protect the river and the sea, as well as to manage use of the river water, 11 nations made an agreement among themselves and the European Union. They agreed to cooperate to prevent pollution of the water and to conserve and use water from the Danube sensibly. They also agreed to conserve and protect groundwater. Some national and international water pollution problems are hard to solve. States in the northeastern United States are concerned about acid rain. Particle pollution from factories to the west is collected in clouds. Then the wind blows the clouds across the Eastern states, and acid rain falls in lakes and rivers that are far from the source. The acid rain can kill plants, as well as fish and other animals. Chapter 3: Freshwater Resources 105
Desalination by Evaporation collection trough
1
Sunlight heats up seawater.
3
2 2
Heated water evaporates, and salt is left behind.
fresh water
1
seawater
seawater fresh water
3
Water vapor saturates air and condenses. Fresh water falls into collection troughs. Salt is removed periodically.
VOCABULARY Add a description wheel for desalination in your notebook.
New Sources Can people find new sources of fresh water? The answer, at first, seems obvious. Just remove the salt from seawater. In dry regions, such as Israel, Lebanon, and some coastal towns in California and Florida, people are trying to obtain fresh water this way. The process of removing salt from ocean water is called desalination (dee-SAL-ih-NAY-shun). Some treatment plants use a method similar to the natural water cycle. Salt water is evaporated, and salt is left behind. Then water vapor is condensed, or returned to liquid form, as fresh water. If this process were easy and inexpensive, water shortages might never happen. However, desalination can cost five times as much as normal water treatment. Therefore, it is not a solution that will work for most countries. As technology improves, the cost may go down. Another possible source of fresh water is icebergs. Icebergs contain millions of liters of fresh water. However, the process of towing an iceberg to a city before it melts is too expensive to be practical.
KEY CONCEPTS
CRITICAL THINKING
1. What is drought and what problems does it cause?
4. Connect Draw up a plan that suggests three ways to conserve water at your school. Be sure your ideas are practical, and explain how you might convince people to make the changes.
2. How are aquifers and rivers being depleted? 3. Name two ways to help prevent water shortages.
106 Unit 1: Earth’s Waters
5. Infer Why do you think some people object to building a water pipeline from Alaska to California?
CHALLENGE 6. Synthesize Think about what you have learned about national and international water issues. Then think about what you know about aquifers. What usage problems might occur when one aquifer lies under two countries? How might people solve any problems that arise?
Water shortages threaten society. Sunshine State STANDARDS SC.D.1.3.1: The student knows how conditions that exist in one system influence the conditions that exist in other systems. SC.D.2.3.1: The student understands that quality of life is relevant to personal experience.
BEFORE, you learned
NOW, you will learn
• Water is treated for drinking • Wastewater is treated and released • Pollutants contaminate the water supply
• How overuse causes water shortages • How water can be conserved • How governments and organizations manage water use
EXPLORE The Value of Fresh Water
Does water cost more than gasoline? PROCEDURE
VOCABULARY drought p. 101 desalination p. 106
1
Find out the current price of a liter of bottled water.
MATERIALS calculator
2 Find out the current price of a gallon
of gasoline. 3 To calculate the price of gasoline in
liters, multiply the price per gallon by 0.26.
WHAT DO YOU THINK? • How do the prices of bottled water and gasoline compare? • What do your results tell you about the value of drinking water?
Water shortages are a global problem. SUPPORTING MAIN IDEAS Support the main idea of global water shortages with details and examples.
Most nations in the deserts of northern Africa and in the Middle East have severe water shortages. These are some of the driest regions on Earth, but their populations require more and more water as cities grow. Water that could be used to grow food is piped instead to the growing cities, where it is needed in homes and factories. So how do people in these regions grow enough food? For the most part, they cannot. There is simply not enough water. Jordan imports, or brings in from other countries, about 91 percent of its grain. Israel imports about 87 percent, and Egypt, once a center of agriculture, imports 40 percent.
100 Unit 1: Earth’s Waters
All over the world, the water supply is dwindling. Populations are growing everywhere, and people must be fed. Farmers draw water from underground aquifers faster than the water can be replaced. Even places that normally get regular rainfall can face water shortages. Drought (drowt) is a long period of abnormally low rainfall. Drought can destroy crops and dry up water supplies. Usually, trees can survive a dry period because their roots reach into the ground for water. However, severe drought can dry out entire forests. Dry trees are more vulnerable to disease, and wildfires are harder to control.
Overuse can cause water shortages. As the world’s population grows, usable fresh water is becoming scarcer in many places. Agriculture uses two-thirds of the world’s available fresh water. Unfortunately, only half of that water reaches the roots of the plants. The other half is lost to evaporation and runoff.
MARYLAND
Overuse of underground water can cause an aquifer to be depleted, or consumed faster than its water is replaced. In most places where crops require irrigation, farmers water their fields with groundwater. India is using twice as much water from its aquifers as can be replaced. In the United States, farmers are taking so much water that they are draining the huge Ogallala Aquifer. The problem is that underground stores of water can take thousands of years to refill. Draining an aquifer can also destroy it. When water is removed, the ground may settle and close up the storage space.
A bridge stands over a dried-out part of a reservoir during a drought in Maryland.
River water is also being overused in many places. So much water is being taken out that many major rivers now run dry for a large part of the year. These rivers include the Ganges River in South Asia, the Indus River in Pakistan, and the Colorado River in the southwestern United States. People in seven western states use water from the Colorado. As cities in these states have grown, the demand for the river water has increased. How has overuse of water affected some rivers?
Chapter 3: Freshwater Resources 101
Fresh water can be conserved. SUPPORTING MAIN IDEAS Record in your notes the important details about water conservation.
Although water shortages are a serious problem, the situation is not entirely hopeless. Conserving can solve a big part of the problem. Conservation is action taken to protect and preserve the natural world. To conserve water means to use less of it. U.S. Household Water Usage Americans use an average of 168 liters per person each day.
toilet flushes 29%
toilet leaks 5% dishwashing 3% bath 9%
washing machine 21%
tap 12% shower 21%
SOURCE: U.S. Environmental Protection Agency
The chart above shows how Americans use water each day. The amount that each American uses on average—168 liters—is higher than in most parts of the world. Note that 5 percent of the amount—more than 8 liters—is wasted by leaking toilets.
These water-catching devices are used to collect and store rainwater in Hawaii.
The Need for Conservation Think about what you already know about the water cycle. When aquifers, lakes, and rivers are depleted—or used up faster than the water in them can be replaced naturally—available fresh water from those water supplies decreases. Because water supplies in many regions are being depleted, conservation is an urgent issue. Much of the western United States is mostly desert, and yet the population in dry parts of the West is growing each year. What will happen if the aquifers and rivers that supply this region with water dry up? The less water that people use today, the more water there will be to use in the future. Water shortages are an increasing problem around the world as the population grows in many regions. About half a billion people in 31 countries—mostly in the Middle East and Africa—currently face water shortages. By 2025, the number of people without enough water will increase five times, to about 2.8 billion people.
102 Unit 1: Earth’s Waters
Conservation Practices People conserve water in three ways. The first way is to use less water. Some cities conserve their supply of water simply by repairing leaks in underground pipes. The second way is to reuse water. Many cities reuse treated wastewater for landscaping. The third method is to recycle water, or use water again for the same purpose.
RESOURCE CENTER CLASSZONE.COM
Learn more about water conservation.
Farmers can conserve water by using drip irrigation instead of spraying water. They can change the grooves in their fields so the water stays in the soil longer. Most industries can use water at least twice before returning it to a river or lake. For example, water used to cool machines can be recycled back through the same system. At home, people can change their plumbing and their habits. Low-flow toilets and showerheads can cut water use in half. People conserve water by turning off the faucet while brushing their teeth, taking shorter showers, and running the dishwasher only when it is full. Leaking pipes and dripping faucets in homes cause huge amounts of water to be wasted. Repair and maintenance of plumbing systems would reduce water use greatly. Check Your Reading
What are the three main ways in which people conserve water?
Water Conservation How much water does a dripping faucet use? 1
Adjust a faucet so that water drips slowly.
2
Set a container under the faucet and collect the dripping water for five minutes.
3
Turn off the faucet. Use the graduated cylinder to measure how much water dripped. Record your results in milliliters.
4
Multiply the amount by 12 to determine how much water would drip in an hour. Then divide that number by 1000 to convert your result to liters.
SKILL FOCUS Measuring
MATERIALS • • • •
water faucet container funnel 100 mL graduated cylinder
TIME 20 minutes
WHAT DO YOU THINK? • How much water would one leaky faucet waste in a day? • In a town with 2000 houses with one leaky faucet in each, how much water would be wasted each day?
CHALLENGE How could you combine your results with those of your classmates to make the results more reliable?
Chapter 3: Freshwater Resources 103
People can balance water needs and uses. People around the world have different views about how water should be used. Americans in the hot Southwest might want water for swimming pools and lawns. Developing countries need water to prevent disease and grow food. In some places, farmers use river water before it can reach others downstream. Some industries want water to make products. As water becomes scarcer, the arguments become more serious. Public officials and experts can help manage water use and enforce fair laws. For example, what happens when a river flows from one state into another or across a national border? In such a situation, people must agree to share the water rights. The Rio Grande flows through two states and then between Texas and Mexico. The water in this river is an international issue. In 1939 a legal agreement was made between the states of Colorado, New Mexico, and Texas, and between the United States and Mexico. It listed how much water each region could take. In the past, water from the Rio Grande was used for farming. However, cities along the river are growing rapidly. All the cities need more water from the Rio Grande, and every year they will need more. The international agreement no longer solves this urgent problem. American and Mexican officials are looking for new solutions.
Much Demand for the Rio Grande Three states and Mexico share the water of the Rio Grande. The Rio Grande begins its flow in Colorado. The agreement states that Colorado must allow a certain amount of water to flow into New Mexico.
By 2050 the population of Ciudad Juárez, Mexico, could be larger than all of New Mexico’s population.
104 Unit 1: Earth’s Waters
New Mexico’s largest city, Albuquerque, continues to expand, increasing demand for Rio Grande water.
New Mexico has dams and reservoirs to store reserves of water.
So much water is used upstream that the riverbed between El Paso and Presidio, Texas, is sometimes dry.
Shortages When there is not enough water, crops will not grow. And when the crops fail to grow, there is not enough food to eat. The Middle East countries that import most of their grain are, in a way, importing water. Billions of tons of water are used to grow the imported grain. International organizations help out countries where drought and floods have destroyed the crops. For example, in 2002 the World Food Programme alerted the world to a serious lack of food in southeast Africa. The United Nations agencies arranged for food aid. The shrinking of Lake Chad has also caused hardship for many Africans. In the future, people may solve some of the problems by sharing water around the world. The governor of Alaska has suggested an undersea pipeline. This line would be between 2200 kilometers (1360 mi) and 3400 kilometers (2100 mi) long. Through this pipe, thousands of liters of fresh water would flow from Alaska to California. Some people have also suggested selling Great Lakes water to Japan. Many people in states and Canadian provinces around the lakes have strongly objected, because they think removing water could damage the lakes. check your reading
Lake Chad
This satellite photograph of Lake Chad in Africa was taken in 1973.
How can Alaska help solve a water shortage in California?
Pollution A recent photograph shows how Where water flows across the boundaries of nations, much the lake has shrunk. pollution can flow across as well. One example of this problem is the Danube River in Europe. This river begins in the Black Forest in Germany. It empties into the Black Sea on the coast of Romania. As it flows through the cities of Vienna, Budapest, and Belgrade, more and more pollution is added to the water. Seventeen countries border either the Danube River or the Black Sea. To protect the river and the sea, as well as to manage use of the river water, 11 nations made an agreement among themselves and the European Union. They agreed to cooperate to prevent pollution of the water and to conserve and use water from the Danube sensibly. They also agreed to conserve and protect groundwater. Some national and international water pollution problems are hard to solve. States in the northeastern United States are concerned about acid rain. Particle pollution from factories to the west is collected in clouds. Then the wind blows the clouds across the Eastern states, and acid rain falls in lakes and rivers that are far from the source. The acid rain can kill plants, as well as fish and other animals. Chapter 3: Freshwater Resources 105
Desalination by Evaporation collection trough
1
Sunlight heats up seawater.
3
2 2
Heated water evaporates, and salt is left behind.
fresh water
1
seawater
seawater fresh water
3
Water vapor saturates air and condenses. Fresh water falls into collection troughs. Salt is removed periodically.
VOCABULARY Add a description wheel for desalination in your notebook.
New Sources Can people find new sources of fresh water? The answer, at first, seems obvious. Just remove the salt from seawater. In dry regions, such as Israel, Lebanon, and some coastal towns in California and Florida, people are trying to obtain fresh water this way. The process of removing salt from ocean water is called desalination (dee-SAL-ih-NAY-shun). Some treatment plants use a method similar to the natural water cycle. Salt water is evaporated, and salt is left behind. Then water vapor is condensed, or returned to liquid form, as fresh water. If this process were easy and inexpensive, water shortages might never happen. However, desalination can cost five times as much as normal water treatment. Therefore, it is not a solution that will work for most countries. As technology improves, the cost may go down. Another possible source of fresh water is icebergs. Icebergs contain millions of liters of fresh water. However, the process of towing an iceberg to a city before it melts is too expensive to be practical.
KEY CONCEPTS
CRITICAL THINKING
1. What is drought and what problems does it cause?
4. Connect Draw up a plan that suggests three ways to conserve water at your school. Be sure your ideas are practical, and explain how you might convince people to make the changes.
2. How are aquifers and rivers being depleted? 3. Name two ways to help prevent water shortages.
106 Unit 1: Earth’s Waters
5. Infer Why do you think some people object to building a water pipeline from Alaska to California?
CHALLENGE 6. Synthesize Think about what you have learned about national and international water issues. Then think about what you know about aquifers. What usage problems might occur when one aquifer lies under two countries? How might people solve any problems that arise?
