SUPPLY, RENEWAL, AND USE WATER RESOURCES

HOW MUCH IS AVAILABLE? 97.4% is salt water 2.6% is fresh water Locked in ice caps and glaciers Polluted Salty or deep groundwater 0.014% available as soil moisture, useable groundwater, water vapor, and surface water

PLANET’S WATER BUDGET

WATER RESOURCES ARE UNEVENLY DIVIDED IN THE WORLD HYDROLOGIC CYCLE FILTERS AND RECYCLES FRESHWATER

WATER SHORTAGES Water haves and have nots Average annual precipitation divide the world’s continents, countries, and people Some places receive a lot of rain, others very little Example: Canada has only 0.5% of the world’s population but 20% of the world’s freshwater. China has 20% of the world’s population but only 7% of the water supply.

USABLE WATER Surface Water Any precipitation that does not infiltrate into the ground 1/3 is reliable runoff 2/3 is lost by seasonal floods Watershed or Drainage Basin Region where water drains into a stream, lake, reservoir, wetland, etc. Ground Water Water that infiltrates into the ground, fills up pores in rock and soil Area above impermeable rock barrier is the Zone of Saturation Water table—on top of zone of saturation Zone of Aeration—above the water table (air and 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 Confining permeable rock layer Unconfined Aquifer Recharge Area

HOW IS WATER USED WORLDWIDE? Mostly for irrigation (70%) Industry (20%) Cities and Residences (10%)

1 automobile 1 kilogram cotton 1 kilogram aluminum 1 kilogram grain-fed beef 1 kilogram rice 1 kilogram corn 1 kilogram paper 1 kilogram steel 400,000 liters (106,000 gallons) 10,500 liters (2,400 gallons) 9,000 liters (2,800 gallons) 7,000 liters (1,900 gallons) 5,000 liters (1,300 gallons) 1,500 liters (400 gallons) 880 liters (230 gallons) 220 liters (60 gallons) Amount of water needed to produce some common agricultural and manufactured products.

WATER PROBLEMS IN THE U.S. Eastern states have ample precipitation Mainly used for energy production, cooling, and manufacturing Flooding, occasional urban shortages, pollution Western states have too little precipitation Mainly used for irrigation Shortage of runoff caused by low precipitation, high evaporation, drought

PREVENTING WATER SHORTAGES Water shortages are caused by Drought—21 days or longer where precipitation is at least 70% below normal Desiccation of soil—deforestation and overgrazing Water stress—too many people and not enough water Increase water supply by Build dams and reservoirs to store runoff Bring surface water from other areas Withdraw groundwater Convert salt water to fresh water Improve efficiency of water use

DAMS

USING DAMS Benefits Control floods Produce hydroelectric power Supply water for irrigation Recreation (swimming, fishing, and boating) Drawbacks Reduces water flow below the dam Silting at the dam Increase risk of flooding if dam breaks Destroys natural ecosystems Increases water pollution Promotes saltwater intrusion

USING TRANSFER OF WATER Tunnels, aqueducts, and pipes

USING GROUNDWATER Pros—can be removed year round, is not lost by evaporation, less expensive to develop than surface water systems Cons—lowers the water table, land subsidence, salt water intrusion, moves contaminated chemicals toward wells, reduces stream flow

USING DESALINIZATION Removing dissolved salts from ocean water or brackish groundwater Distillation Reverse osmosis Main plants are in the Middle East and North Africa Energy expensive Produces much waste water (brine)