Water Resources

Questions for Today: What are the major reasons for the decline of freshwater resources? What are the major reasons for the decline of freshwater resources? What are the different ways to get freshwater? What are the different ways to get freshwater? How do we use freshwater more sustain ably? How do we use freshwater more sustain ably?

Decline of Freshwater Water is a renewable resource! Water is a renewable resource! –Tragedy of the Commons can take effect though. Most of our usable water comes from groundwater sources like aquifers. Most of our usable water comes from groundwater sources like aquifers. –Decline in aquifer levels are due to over pumping and wasteful irrigation.

U.S. Depletion In the United States, Groundwater is being drafter 4 times as faster than it can be replenished. In the United States, Groundwater is being drafter 4 times as faster than it can be replenished. One of the largest overdrafts comes from the Ogallala Aquifer. One of the largest overdrafts comes from the Ogallala Aquifer. –Stretches from South Dakota to Texas

Fig , p. 323 WYOMING SOUTH DAKOTA NEBRASKA COLORADO KANSAS OKLAHOMA NEW MEXICO Miles TEXAS Saturated thickness of Ogallala Aquifer Less than 61 meters (200 ft.) 61–183 meters (200–600 ft.) More than 183 meters (600 ft.) (as much as 370 meters or 1,200 ft. in places) Kilometers

Other problems due to overpumping: Aside from economics due to overpumping, one of the biggest secondary problems for over pumping comes in land subsidence. Aside from economics due to overpumping, one of the biggest secondary problems for over pumping comes in land subsidence. Sinkholes can form from over pumping. Sinkholes can form from over pumping. –Occurred in San Antonio this year. San Antonio San Antonio –Slanted Church in Mexico Mexico

What are different ways to get new freshwater Build Dams Build Dams –Refresh memory –Dam Problems (HA!) Colorado disappearing (14 dams) Colorado disappearing (14 dams) Transfer Water Transfer Water –Aral Sea Disappearing

Natural Capital Degradation: The Aral Sea, Shrinking Freshwater Lake

What are different ways to get new freshwater Desalinate Water Desalinate Water – –Distillation – –Reverse osmosis, microfiltration –Problems High cost and energy footprint High cost and energy footprint Keeps down algal growth and kills many marine organisms Keeps down algal growth and kills many marine organisms Large quantity of brine wastes Large quantity of brine wastes

Living Sustainably Reduce Waste Water Reduce Waste Water –Domestically –Agriculturally

Fig , p. 335 Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Drip irrigation (efficiency 90–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Gravity flow (efficiency 60% and 80% with surge valves) Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually comes from an aqueduct system or a nearby river.