All of Earth's water. ⢠Oce
ENVIR SCI 1A03
February 12, 2014 Hydrologic Cycle and Water Balance
What is the Hydrosphere? • All of Earth’s water. • Ocean – 97% of all water, freshwater – most in glaciers and ice caps, surface freshwater are in streams or lakes. • Hydrologic Cycle o Over the ocean – 86% evaporation, clouds will form and cloud will move from over ocean to land and the transfer between land and atmosphere are going to be balanced. o The movement on the land by slopes balances the net transfer between the atmosphere and the land. Where does Rainwater go on Land? • Water can be absorbed by plants or evaporated = evapotranspiration • Can infiltrate the ground and percolate downward and fill pore spaces and recharge water table and form water table • Move at the surface – runoff as overland flows, inter flow is just beneath the ground surface What is a Water Balance? • Represents: hydrological cycle at the local state • Accounts for interactions with the available energy and moisture at the Earth’s surface • Take into account moisture and latent heat • Take a look at all the energy the system provides – output, input and storage What is the Water Balance Equation? • P = (PE – D) + S +/- ΔST • D = PE – AE • P – precipitation, PE – potential evapotranspiration (amount of moisture that could potentially evaporate at a given temperature), D – deficit (moisture shortage), S - surplus (oversupply, soil moisture at its full capacity), ΔST- soil moisture storage change (moisture saving, snowpack, reservoirs), AE – actual evapotranspiration, if all demand is satisfied AE=PE • Deficit and Surplus o Deficit occurs when PE cannot be satisfied through P, soil moisture o if growing crops, you need to find additional water for crops and irrigation is needed o Under ideal conditions: AE and PE are close
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o Surplus is when PE is satisfied and ST is full – groundwater is going to be recharged and raise the water table Soil Storage and PE o ACCWL: accumulated potential water loss o All water in the form of P is not enough to meet the demand from the atmosphere o Water taken from ST when P< PE o Field capacity – all the spaces are filled o Wilting point – water unavailable to plants
Sample Budgets • Ultimately want the water to be balanced, input = output • Kingsport, Tennessee o A lot of moisture in this area o Look at graph on slides Saskatoon – typical continental water balance What effect does a large ST have on a location as compared with another location that has the same P and PE totals but a lower ST? – exam • Soil moisture to evaporate to the atmosphere How do impervious surfaces such as parking lots impact the water balance terms? • ST and AE
February 12, 2014 Hydrologic Cycle and Water Balance
What is the Hydrosphere? • All of Earth’s water. • Ocean – 97% of all water, freshwater – most in glaciers and ice caps, surface freshwater are in streams or lakes. • Hydrologic Cycle o Over the ocean – 86% evaporation, clouds will form and cloud will move from over ocean to land and the transfer between land and atmosphere are going to be balanced. o The movement on the land by slopes balances the net transfer between the atmosphere and the land. Where does Rainwater go on Land? • Water can be absorbed by plants or evaporated = evapotranspiration • Can infiltrate the ground and percolate downward and fill pore spaces and recharge water table and form water table • Move at the surface – runoff as overland flows, inter flow is just beneath the ground surface What is a Water Balance? • Represents: hydrological cycle at the local state • Accounts for interactions with the available energy and moisture at the Earth’s surface • Take into account moisture and latent heat • Take a look at all the energy the system provides – output, input and storage What is the Water Balance Equation? • P = (PE – D) + S +/- ΔST • D = PE – AE • P – precipitation, PE – potential evapotranspiration (amount of moisture that could potentially evaporate at a given temperature), D – deficit (moisture shortage), S - surplus (oversupply, soil moisture at its full capacity), ΔST- soil moisture storage change (moisture saving, snowpack, reservoirs), AE – actual evapotranspiration, if all demand is satisfied AE=PE • Deficit and Surplus o Deficit occurs when PE cannot be satisfied through P, soil moisture o if growing crops, you need to find additional water for crops and irrigation is needed o Under ideal conditions: AE and PE are close
•
o Surplus is when PE is satisfied and ST is full – groundwater is going to be recharged and raise the water table Soil Storage and PE o ACCWL: accumulated potential water loss o All water in the form of P is not enough to meet the demand from the atmosphere o Water taken from ST when P< PE o Field capacity – all the spaces are filled o Wilting point – water unavailable to plants
Sample Budgets • Ultimately want the water to be balanced, input = output • Kingsport, Tennessee o A lot of moisture in this area o Look at graph on slides Saskatoon – typical continental water balance What effect does a large ST have on a location as compared with another location that has the same P and PE totals but a lower ST? – exam • Soil moisture to evaporate to the atmosphere How do impervious surfaces such as parking lots impact the water balance terms? • ST and AE
