Chapter 7 Water: Hydrologic Cycle and Human Use Copyright © 2008 Pearson Prentice Hall, Inc.

? What Happened?

What do the following mighty bodies of water have in common? Aral Sea Dead Sea Rio Grande River Colorado River

7.1 - Water: A Vital Resource

Lake Baikal

Located in Russia. Most voluminous freshwater lake in the world. Contains 20% of world’s unfrozen surface water. 5,387 feet at its deepest point.

7.2 - Polarity in H 2 O: The Water Molecule O HH covalent bond

Condensation O HH O HH O HH ++ --

Temperature determines whether water is a… Gas: steam, water vapor Liquid: running water Solid: ice Why does ice float? It is less dense than liquid water. The hydrogen bonds adjust to keep the negative oxygen atoms far enough apart as the temperature falls. Therefore, water expands as it freezes.

The Water Cycle

A B C D E Water Cycle Review F G H

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

Global Precipitation

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

Global Air Circulation

Tropical Atmospheric Circulation Hadley Cell (click to view animation)

Rain Shadow Effect

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

Human Impacts on the Hydrological Cycle

Wetlands Definition - an ecosystem with soil that is either permanently or seasonally saturated with moisture. They are considered the most biologically diverse of all ecosystems. Examples – swamps, estuaries, marshes, and bogs. Benefits: 1.Provide flood control. 2.Filter/clean water. 3.Habitat and nursery for many organisms.

Estuaries Definition – area where freshwater (usually a river) empties into saltwater (usually a bay or ocean). Examples – mangroves and salt marshes Constant changes in temperature and salinity. Why? 1.Daily tides 2.Storms – hurricanes (storm surge), thunderstorms (runoff) 3.Change in seasons 4.Drought Benefits – same as other wetlands.

7.3 - A Resource to Manage, a Threat to Control

Trends in Population and Freshwater Withdrawals, U.S.

Regional Usage of Water

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

Surface Waters Dam impacts (next slides) Ecological effects of changing salinity in estuaries. Increased salinity Loss of native species Invasive species increase

Glen Canyon Dam

Upper Klamath Lake Before Diversion

Upper Klamath Lake After Diversion

James Bay, Quebec Probably the worst environmental damage due to hydroelectric dams in the world. Multiple rivers were blocked starting in the early 1970’s. Native people lost their land. Mercury pollution resulted from flooded forests (trees storing mercury released it into the water). Wildlife with high mercury levels eaten by the native people : ( Local climate change occurred (cooler Springs and warmer Falls).

Consequences of Overdrawing Groundwater Falling water tables Diminishing surface waters (wetlands) Land subsidence Saltwater intrusion

Center Pivot Irrigation 10,000 gallons/minute

Aerial View of Center Pivot Irrigation Sites

Aquifer Exploitation Ground water use exceeds aquifer recharge. Ex. Ogallala aquifer Many remaining aquifers are heavily polluted

Sinkhole

Saltwater Intrusion

7.4 - Dams Three Gorges Dam Largest in world Controls deadly floods Displaced 1.2 million people including farms, cities, homes, and factories 370 mile-long reservoir

Dam Construction

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

Desalination - Desalting Seawater Reverse osmosis Distillation

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

National Water Policy United States must respond to global water crisis Promote water efficiency Reduce or eliminate water subsidies Charge polluters Add watershed management to pricing of water *Clean Water Act - deals with pollution NOT the quantity of water

Educational Programs Needed: the origin of the community water supply and what processes are involved in providing a continuous supply to residents. water consumption rates for various resident activities including business, recreational, and household uses. opportunities for water conservation at the community, residential, and personal levels. multiple water-use strategies that reduce withdraw rates for community water sources, e.g., use of “gray water.” the technologies required to replicate nature’s water filters. adoption of alternative water-use lifestyles such as xeriscaping