Sustainable Water Use & Global Water Resources Ch. 13

How can we use water more sustainably? Cut water waste Raise water prices Slow population growth Protect aquifers Protect forests & other ecosystems

Benefits of Reducing Water Waste ½ - ⅔ of water is wasted Subsidies mask true costs of water Water conservation –Improves irrigation efficiency –Improves collection efficiency –Uses less in homes and businesses

We Can Cut Water Waste in Irrigation Flood irrigation –Wasteful Center pivot, low pressure sprinkler Low-energy, precision application sprinklers Drip or trickle irrigation, microirrigation –Costly; less water waste

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 fl ow (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.

Less-Developed Countries Use Low- Tech Methods for Irrigation - Human-powered treadle pumps Treadle Pump in Bangladesh

Less-Developed Countries Use Low- Tech Methods for Irrigation - Harvest and store rainwater

Less-Developed Countries Use Low- Tech Methods for Irrigation - Create a polyculture canopy over crops: reduces evaporation

We Can Cut Water Waste in Industry and Homes Recycle water in industry Fix leaks in the plumbing systems Use water-thrifty landscaping: xeriscaping Use gray water Pay-as-you-go water use

Too Much Water? How can we reduce the threat of flooding? –Protect wetlands –Protect natural vegetation –Don’t build in areas with frequent flooding

Too Much Water? Flood plains –Highly productive wetlands –Provide natural flood and erosion control –Maintain high water quality –Recharge groundwater Benefits of floodplains –Fertile soils –Nearby rivers for use and recreation –Flatlands for urbanization and farming

Too Much Water? Human activities make floods worse –Levees can break or be overtopped –Paving and development increase runoff –Removal of water-absorbing vegetation –Draining wetlands and building on them –Rising sea levels from global warming means more coastal flooding

Diverse ecological habitat Evapotranspiration Trees reduce soil erosion from heavy rain and wind Tree roots stabilize soil Vegetation releases water slowly and reduces flooding Forested Hillside Agricultural land Stepped Art Tree plantation Roads destabilize hillsides Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil Agricultural land is flooded and silted up Gullies and landslides Heavy rain erodes topsoil Silt from erosion fills rivers and reservoirs Rapid runoff causes flooding After Deforestation Evapotranspiration decreases Fig , p. 340 Too Much Water?

Global Water Use Surface water is considered a global resource that should be shared. How are different areas using their water?

Case Study Jigsaw Colorado River Basin Yangtze River – Three Gorges Dam US Ogallala Aquifer Aral Sea in Former Soviet Union

Colorado River Basin

Case Study

Yangtze River – Three Gorges Dam

Case Study

Ogallala Aquifer

Case Study

Aral Sea*

Case Study