Chapter 14 Water

Core Case Study: Water Conflicts in the Middle East - A Preview of the Future One of the world’s highest population growth rates water shortages Main supply: Nile, Tigris, Jordan Figure 14-1

Water Conflicts in the Middle East: A Preview of the Future Disagreement about water rights. Currently No cooperative agreements for use of 158 of the world’s 263 water basins that are shared by two or more countries.

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL Water: life, moderates climate, sculpts land, removes/dilutes wastes and pollutants, hydrologic cycle. 0.02% = liquid freshwater

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL Figure 14-2

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL The land from which the surface water drains into a body of water is called its watershed or drainage basin. Groundwater exists too.

Unconfined Aquifer Recharge Area Evaporation and transpiration Precipitation Evaporation and transpiration Evaporation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Figure 14.3 Natural capital: groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure. Some aquifers are replenished by precipitation; others are not. Infiltration Water table Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining impermeable rock layer Fig. 14-3, p. 308

Animation: Threats to the Aquifers Animations/aquifers.html

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL 70% water withdrawn from rivers, lakes, and aquifers is not returned to these sources. Irrigation (70%), industries (20%) and cities and residences (10%). Currently >50% of the world’s reliable runoff is used 70-90% by 2025.

Figure 14-4

Case Study: Freshwater Resources in the United States 17 western states face potential intense water conflict urban growth, irrigation, recreation and wildlife. Figure 14-5

TOO LITTLE FRESHWATER 41% of the world’s population lives in river basins that do not have enough freshwater. Rivers running dry. Lakes and seas shrinking. Falling water tables (overpumped aquifers)

Stress on the World’s River Basins Comparison of the amount of water available with the amount used by humans. Figure 14-6

Case Study: Who Should Own and Manage Freshwater Resources Controversy: government owned and managed or private corporations. European-based water companies aim to control 70% of the U.S. water supply.

TOO LITTLE FRESHWATER Cities are outbidding farmers. Countries are importing grain. More crops used for biofuels. Options: Get more water from aquifers and rivers, desalinate ocean water, waste less water.

WITHDRAWING GROUNDWATER TO INCREASE SUPPLIES Most aquifers are renewable Unless water is removed faster than replenished Or contaminated. Groundwater depletion - growing problem Irrigation. One-fourth of the farms in India irrigated from overpumped aquifers.

Withdrawing Groundwater Trade-Offs Withdrawing Groundwater Advantages Disadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Sinking of land (subsidence) from overpumping Available year-round Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas Figure 14.7 Trade-offs: advantages and disadvantages of withdrawing groundwater. QUESTION: Which two advantages and which two disadvantages do you think are the most important? No evaporation losses Reduced water flows into surface waters Increased cost and contamination from deeper wells Cheaper to extract than most surface waters Fig. 14-7, p. 313

Groundwater Depletion: A Growing Problem Areas of greatest aquifer depletion (overdraft)

OGALLALA

Other Effects of Groundwater Overpumping Sinkholes (subsidence) Contamination with saltwater. (salt water intrusion) Figure 14-11

Other Effects of Groundwater Overpumping Figure 14-10

Groundwater Pumping in Saudi Arabia (1986 – 2004) Irrigation systems Nonrenewable aquifer = green dots Dried wells = Brown dots Figure 14-9

Groundwater Depletion Solutions Groundwater Depletion Prevention Control Waste less water Raise price of water to discourage waste Subsidize water conservation Ban new wells in aquifers near surface waters Tax water pumped from wells near surface waters Buy and retire groundwater withdrawal rights in critical areas Figure 14.12 Solutions: ways to prevent or slow groundwater depletion by using water more sustainably. QUESTION: Which two of these solutions do you think are the most important? Set and enforce minimum stream flow levels Do not grow water-intensive crops in dry areas Fig. 14-12, p. 316

USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER Large dams and reservoirs cheap electricity reduce downstream flooding year-round water for irrigating cropland displace people disrupt aquatic systems.

Provides water for year-round irrigation of cropland Flooded land destroys forests or cropland and displaces people Large losses of water through evaporation Provides water for drinking Downstream cropland and estuaries are deprived of nutrient-rich silt Reservoir is useful for recreation and fishing Risk of failure and devastating downstream flooding Can produce cheap electricity (hydropower) Figure 14.13 Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Downstream flooding is reduced Migration and spawning of some fish are disrupted Fig. 14-13a, p. 317

Powerlines Reservoir Dam Powerhouse Intake Turbine Fig. 14-13b, p. 317 CLICK ON THIS: http://techalive.mtu.edu/meec/demo/HydroelectricDam.html Dam Powerhouse Intake Turbine Figure 14.13 Trade-offs: advantages (green) and disadvantages (orange) of large dams and reservoirs. The world’s 45,000 large dams (higher than 15 meters or 50 feet) capture and store 14% of the world’s runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used by 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Fig. 14-13b, p. 317

Case Study: The Colorado Basin – an Overtapped Resource The Colorado River 14 major dams and reservoirs, and canals. Used in desert area of the U.S. Hydroelectric plants for 30 million people (1/10th of the U.S. population). Often doesn’t reach Gulf of California

Case Study: The Colorado Basin – an Overtapped Resource Lake Powell, 2nd largest reservoir in the U.S. Hydroelectric plant Figure 14-15

The Colorado River Basin Drainage basin covers more than one-twelfth of the land area of the lower 48 states. Figure 14-14

Case Study: China’s Three Gorges Dam DEBATE – world’s largest dam Dam 2 km long. The electric output = 18 large coal-burning or nuclear power plants. Facilitate ship travel, reduce transportation costs. Displace 1.2 million people. Built over seismatic fault, already has small cracks.

Dam Removal Some for ecological reasons Some outlived their usefulness. In 1998 the U.S. Army Corps of Engineers – no more large dam projects in US Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. Can reestablish ecosystems Can re-release toxicants into the environment.

TRANSFERRING WATER FROM ONE PLACE TO ANOTHER makes unproductive areas more productive can cause environmental harm. Promotes investment, jobs and strong economy. It encourages unsustainable use

Case Study: The California Experience A massive transfer of water from water-rich northern California to water-poor southern California is controversial. Figure 14-16

Case Study: The Aral Sea Disaster The Aral Sea was once the world’s fourth largest freshwater lake. Figure 14-17

Case Study: The Aral Sea Disaster Diverting water from the Aral Sea and its two feeder rivers Mostly for irrigation 85% of the wetlands have been eliminated 50% of the local bird and mammal species have disappeared. Since 1961, sea’s salinity has tripled water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES Removing salt from seawater = expensive, & large amounts of salty wastewater Distillation: heating saltwater until it evaporates, leaves behind water in solid form. Reverse osmosis: uses high pressure to force saltwater through a membrane filter.

DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND GIANT BAGGIES Seeding clouds with tiny particles of chemicals to increase rainfall – AgNO3 towing icebergs or huge bags filled with freshwater to dry coastal areas unlikely to provide significant amounts of freshwater.

INCREASING WATER SUPPLIES BY WASTING LESS WATER We waste about two-thirds of the water we use 65-70% lost through evaporation, leaks, and other losses. Water is underpriced thru government subsidies. Lack of subsidies for improving efficiency contributes to water waste.

INCREASING WATER SUPPLIES BY WASTING LESS WATER 60% of the world’s irrigation water is currently wasted Improved techniques could cut this to 5-20%. Center-pivot, low pressure sprinklers sprays water directly onto crop. It allows 80% of water to reach crop. Has reduced depletion of Ogallala aquifer in Texas High Plains by 30%.

(efficiency 60% and 80% with surge valves) Drip irrigation Gravity flow (efficiency 60% and 80% with surge valves) Figure 14.18 Major irrigation systems: because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new low-cost drip-irrigation systems may change this situation. Center pivot Above- or below-ground pipes or tubes deliver water to individual plant roots. (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers. Water usually comes from an aqueduct system or a nearby river. Fig. 14-18, p. 325

Reducing Irrigation Water Waste Solutions Reducing Irrigation Water Waste • Line canals bringing water to irrigation ditches • Level fields with lasers • Irrigate at night to reduce evaporation • Monitor soil moisture to add water only when necessary • Polyculture • Organic farming Figure 14.19 Solutions: methods for reducing water waste in irrigation. QUESTION: Which two of these solutions do you think are the most important? • Don't grow water-thirsty crops in dry areas • Grow water-efficient crops using drought resistant and salt-tolerant crop varieties • Irrigate with treated urban waste water • Import water-intensive crops and meat Fig. 14-19, p. 326

Solutions: Getting More Water for Irrigation in Developing Countries – The Low-Tech Approach Many poor farmers in developing countries use low-tech methods to pump groundwater and make more efficient use of rainfall. Figure 14-20

Solutions Reducing Water Waste • Redesign manufacturing processes • Repair leaking underground pipes • Landscape yards with plants that require little water • Use drip irrigation • Fix water leaks • Use water meters • Raise water prices • Use waterless composting toilets • Require water conservation in water-short cities Figure 14.21 Solutions: methods of reducing water waste in industries, homes, and businesses. QUESTION: Which three of these solutions do you think are the most important? • Use water-saving toilets, showerheads, and front loading clothes washers • Collect and reuse household water to irrigate lawns and nonedible plants • Purify and reuse water for houses, apartments, and office buildings • Don't waste energy Fig. 14-21, p. 327

Raising the Price of Water: A Key to Water Conservation Reducing water use and waste Raising the price of water When Boulder, Colorado introduced water meters, water use per person dropped by 40%. A 10% increase in water prices cuts domestic water use by 3-7%. Provide low lifeline rates for the poor.

Solutions: Using Less Water to Remove Industrial and Household Wastes Mimic the way nature deals with wastes Instead of using large amounts of high-quality water to wash and dilute industrial and animal wastes. Use nutrients in wastewater as soil fertilizer. Composting toilets convert human fecal matter into a small amount of soil material.

TOO MUCH WATER FLOODS Heavy rainfall rapid snowmelt removal of vegetation destruction of wetlands Natural flood mitigation - Floodplains/wetlands = natural flood and erosion control, maintain high water quality, and recharge groundwater. Artificial flood mitigation narrowing rivers with levees and walls damming to store water.

TOO MUCH WATER Comparison of St. Louis, Missouri under normal conditions (1988) and after severe flooding (1993). Figure 14-22

TOO MUCH WATER Human activities have contributed to flood deaths and damages. Figure 14-23

Animation: Effects of Deforestation Animations/effects_deforestation.html

Preserve forests on watersheds Solutions Reducing Flood Damage Prevention Control Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Build levees or floodwalls along streams Tax all development on floodplains Figure 14.24 Solutions: methods for reducing the harmful effects of flooding. QUESTION: Which two of these solutions do you think are the most important? Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation Build dams Fig. 14-24, p. 331

SOLUTIONS: USING WATER MORE SUSTAINABLY cutting waste raising water prices preserving forests and wetlands slowing population growth. Figure 14-25