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Bdale Envir Ch 14 – Water Resources and Water Pollution - page 2 / 7

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discussion of various components of hydro cycle…Fig 14-3

surface water – lakes, streams, overland flow

groundwater – subsurface flow, some water in aquifers may be thousands of years old…..

how much of the world’s water supply are we using?

Water use has increased almost 10x since 1900….biggest use is irrigation (Fig 14-4)

70% goes to irrigated land

20% goes to industry

10% goes to cities and industries

Freshwater resources in US:

Miller makes point that US has plenty of water, but it is in the “wrong place” or it is getting contaminated (example of Long Island aquifer, supporting 3 million people)

Imbalance: plenty water in eastern US, not enough in western US (fig 14-7)

Western US uses lots of water for irrigation, but does NOT get much through recharge.  So there is the danger of a net loss of water…..especially since people continue to move out west….

14-3 – too little water

what causes shortages of fresh water?

Dry climate

Drought

Dessication of soil

Water “stress”

Stress is low per capita (per person) availability of water

How can freshwater supplies be increased?

Build dams & reservoirs to store water

Bring in water from elsewhere

Increase GW withdrawal

Desalinate salt water

Improve efficiency of use of existing water supplies

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