APES Chapter 14 Water Resources

Water’s Unique Properties  Hydrogenbonding  Hydrogen bonding  Liquid over wide temperature range  Changes temperature slowly  High heat of evaporation  Great dissolving power  Helps regulate pH  Adhesion and cohesion  Expands when it freezes

ALL Because it’s POLAR 3

Supply of Water Resources Fig p. 314 FreshwaterFreshwater Readily accessible freshwater Biota0.0001%Biota0.0001% Rivers0.0001%Rivers0.0001% Atmospheric water vapor %Atmospheric % Lakes % Soil moisture % Groundwater0.592%Groundwater0.592% Ice caps and glaciers 1.984% 0.014%0.014%

What is Surface Water? Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation. –Example: A watershed (drainage basin) is a region from which water drains into a stream, lake, reservoir, wetland, or other body of water. 5

What is Groundwater? Precipitation that infiltrates into the ground and percolates downward through spaces between soil and rock. –Near the surface, these voids contain little moisture. –Deeper, in the zone of saturation, the voids are completely filled with water. 6

The water table is located at the top of the zone of saturation. Porous, water-saturated layers of sand, gravel, or rock are called aquifers. An area of land through which water passed downward into an aquifer is the recharge area. If water is withdrawn from an aquifer faster than it can recharge the aquifer will become depleted. 7

Ground Water Evaporation and transpiration Evaporation Stream Infiltration Water table Infiltration Unconfined aquifer Confined aquifer Lake Well requiring a pump Flowing artesian well Runoff Precipitation Confined Recharge Area Aquifer Less permeable material such as clay Confirming permeable rock layer Fig p. 315

Use of Water Resources  Humans use about 50% of reliable runoff  Agriculture  Industry  Domestic  Power plants Fig p. 316 United States Industry 11% Public 10% Power cooling 38% Agriculture 38%

What causes freshwater shortages?  Dry climate  Drought  Desiccation  Water stress Acute shortage Adequate supply Shortage Metropolitan regions with population greater than 1 million Fig p. 317

How can we increase Freshwater Supplies? Build dams and reservoirs Bring in water from another area Withdraw groundwater Waste less water Import food to reduce water use

Building Dams Advantages Control flooding Produce hydroelectric power Supply water for towns and cities Provide recreational activities such as fishing and boating Disadvantages Large water loss through evaporation Land lost Migration and spawning of some fish disrupted No nutrient-rich silt downstream of dam

Using Dams and Reservoirs to Supply More Water Large losses of water through evaporation Large losses of water through evaporation Flooded land destroys forests or cropland and displaces people Flooded land destroys forests or cropland and displaces people Downstream flooding is reduced Downstream cropland and estuaries are deprived of nutrient-rich silt Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted Provides water for year-round irrigation of cropland Fig p. 319

Transferring water form another area Advantages Supplies water for agricultural, domestic, and industrial needs Disadvantages Degrade rivers Deplete groundwater Threaten fisheries

Tapping Groundwater Advantages Year round supply Not lost by evaporation Less expensive to develop than surface water sources Disadvantages Water table lowering Aquifer depletion Intrusion of salt water into aquifers Reduce stream flow May be contaminated by septic tanks or industrial activities

Desalination Advantages Can provide fresh water from very abundant salt water Disadvantages Very expensive Produces large quantities of wastewater

How Can We Use Water More Efficiently?  Reduce losses due to leakage  Reform water laws  Improve irrigation efficiency ( Fig p. 330 )  Improving manufacturing processes  Water efficient landscaping  Water efficient appliances

Too Much Water: Floods  Natural phenomena Floodplain Levee Flood wall Dam Reservoir  Renew and replenish  Aggravated by human activities Fig p. 332

Solutions: Achieving a More Sustainable Water Future  Efficient irrigation  Water-saving technologies  Improving water management See Fig p. 336