When the well is dry, we learn the worth of water... Benjamin Franklin WATER RESOURCES When the well is dry, we learn the worth of water... Benjamin Franklin

FACTS 71% of the Earth’s surface is covered in oceans 97.5% of Earth’s water is saltwater; 2.5% is freshwater Less than 1% (0.024%) of all freshwater is accessible for our daily use Most freshwater is frozen in glaciers & icecaps or in underground aquifers

Water is not evenly distributed on Earth... 470 inches rainfall per year in Kauai, Hawaii Virtually no rain per year in Atacama Desert, Chile BUT...water is RENEWABLE...hydrologic cycle...water continually recycled BUT...we do not use or manage water in a sustainable manner Overload it with pollutants Remove it/waste it faster than it can replenish (it is thought that 30-50% of all water we use is wasted) Every day we withdraw enough water to fill a convoy of large tankers that would stretch over 300,000 miles

What do we use water for? AGRICULTURE...70% (92% OF Water footprint)... Amount of irrigated land doubled in last 50 yrs Irrigation is inefficient; crops absorb about 40% of the water Over-irrigation leads to waterlogging & soil salinization INDUSTRIAL...20% RESIDENTIAL...10 % Bottled drinking water Why do you choose bottled water over water out of the tap?

POTABLE WATER…. drinkable water VIRTUAL WATER Water that is not directly consumed; used for production of food & other products How much water do you think it takes to make 1 hamburger? 630 gallons...16 bathtubs Look at page 322...complete the table in your notes on the amount of water needed to produce various products Major uses of water in United States Cooling of electric power plants....41% Irrigation...37% Public water...13% Industry...5% Raising livestock...4% POTABLE WATER…. drinkable water

Where does our water come from? GROUND WATER Water that soaks into ground Held within pores of soil/rock Aquifers: large amounts of water found in underground rocks; underground reservoirs Largest in US: Ogalalla Recharge zone...area of land from which groundwater originates Water table: upper limit of groundwater ¼ of water used in US...but supplies ½ drinking water SURFACE WATER Above ground Lakes, ponds, rivers, streams, wetlands WATERSHED: entire area of land that is drained by a river; drainage basin ¾ of water used in US...electricity; municipalities, industrial, irrigation

flooding Can be beneficial Nutrient rich soil Recharge groundwater Maintain wetland biodiversity Freshwater overflows its natural channels to FLOODPLAIN... Fertile soil Flat land Plenty of freshwater Rivers narrowed/channelized; build dikes/levees/dams Increases the impact of flooding....along with other human impacts: Deforestation Draining of wetlands Climate change /sea level rise

CASE STUDIES The Colorado River Story...p. 318 Freshwater Resources in the US...p. 322-323 Overpumping the Ogallala...p. 326-327 How Dams Can Kill an Estuary...p. 331 Aral Sea Disaster: Glaring Example of Unintended Consequences...p. 333-334 Living Dangerously on Floodplains in Bangledesh...p.343- 344

Complete the survey based on your personal water use Water we going to do? Complete the survey based on your personal water use

Water promises to be to the 21st century what oil was to the 20th century: the precious commodity that determines the wealth of nations Fortune magazine may 2000

Solutions addressing freshwater depletion issues Reduce the use & demand focus on water conservation increase efficiency of water use Efficient irrigation... drip irrigation low pressure spray irrigation Line irrigation canals Match crops with land & climate Selective breeding & GMOs (crops that require less water) Recycling treated municipal wastewater (for irrigation of lawns, golf courses, etc Use gray water (wastewater from showers & sinks) to water lawns Install low flow faucets/showerheads/toilets/washing machines Repair leaks in pipes & water mains Automatic dishwashers

Solutions con’t Increase water supply Market based approaches Desalination (but there are several disadvantages: expensive; requires large inputs of fossil fuels; generates salty waste; kill aquatic life at intake Reverse osmosis & distillation Market based approaches End gov’t subsidies of inefficient practices Allow water to become a commodity Privatization of water Individual control; not government control buy, sell, trade water rights Disadvantages: Undersupply the consumer Inequitable distribution Wealthy vs. poor