Environmental Science Toward a Sustainable Future Richard T

Environmental Science: Toward a Sustainable Future Richard T. Wright Chapter 7 Water: Hydrologic Cycle and Human Use PPT by Clark E. Adams

TEST 12/12/07 n HOMEWORK q ALSO DUE REVIEW QUESTIONS n 1 -10

Water: Hydrologic Cycle and Human Use—CHAPTER OBJECTIVES n n Water: a vital resource Hydrologic cycle: natural cycle, human impacts Water: a resource to manage, a threat to control Water stewardship: public-policy challenges

Practice Question? n How much of the Earth is covered with water? n 71% of the Earth Surface is covered with water, 98% of which is salt water we can not drink.

Water: A Vital Resource

Hydrologic Cycle: Natural Cycle, Human Impacts n n n Evaporation, condensation, purification Precipitation Groundwater Pools and fluxes in the cycle Human impacts on the hydrologic cycle

Temperature Determines Whether Water Is a n n n Gas: steam Liquid: running water Solid: ice q Why does ice float?

Basic Facts n n n Warm Air Rises--EVAPORATION Cool Air Falls Creates a Cycle of Moving Air Convection Current Warm air holds more water vapor molecules than cool air.

Condensation

Precipitation n Adiabatic cooling: warm air rises, expands and cools 100% relative humidity + cooling = clouds Increasing condensation = water droplets

Global Precipitation n n Global precipitation distribution depends on patterns of rising and falling air currents Two main factors: q q global convection currents rain shadow effect

The Water Cycle

Practice Question? n Use the following slide to test your knowledge of the hydrologic cycle. q Label your notes n A. n D. n G. B. E. H. C. F.

Water Cycle Review B A D C E F H G

Global Air Circulation

Rain Shadow Effect

Water Balance in the Hydrologic Cycle

Pools and Fluxes in the Cycle D C I E Surface runoff loop F B Ground water H loop A G Evapotranspiration loop

Human Impacts on the Water Cycle n n n Changing the Earth’s surface Floods Climate change Atmospheric pollution Withdrawing water supplies

Groundwater n n n Decreased infiltration Increased runoff Decreased groundwater recharge

Human Impacts on the Hydrologic Cycle

Water: A Resource to Manage, A Threat to Control n n Uses and sources Surface waters

Water Uses

Water Uses

Municipal Water Use and Treatment What is your community’s water source?

Surface Waters n n Dam impacts (see Fig. 7 -15) Ecological effects of changing salinity in estuaries q q q Increased salinity Loss of native species Invasive species increase

Consequences of Overdrawing Groundwater n n Falling water tables Diminishing surface waters (wetlands) Land subsidence (see Fig. 7 -17) Saltwater intrusion

Aquifer Exploitation n n Groundwater use exceeds aquifer recharge Many remaining aquifers are heavily polluted

Saltwater Intrusion

Water Stewardship: Public-Policy Challenges n n Obtaining more water Groundwater Using less water Public-policy challenges

Dams n Three Gorges Dam q q Largest in world Controls deadly floods Displaced 1. 2 million people including farms, cities, homes, and factories 370 -mile-long reservoir

Dams: Disrupt Integrity of River System n Above the dam q q q n Flooding Sediment deposition Loss of functional floodplain Below the dam q q q Loss of normal river flow patterns Loss of river biota Loss of functional floodplain

Using Less Water n Irrigation q q n Surge flow Drip irrigation $$$$ Municipal uses q q Incentives and regulations limiting water use Gray water

Desalting Seawater n n Reverse osmosis Distillation

Public-Policy Challenges

National Water Policy n n Promote water efficiency Reduce or eliminate water subsidies Charge polluters Add watershed management to pricing of water

National Water Policy n n n United States must respond to global water crisis United States must reduce emission of greenhouse gases Need more data for informed policy decisions

End of Chapter 7