Chapter 14 Water

Water’s Unique Properties  Polar covalent molecule  Exists as a liquid over a wide temperature range ( degrees Celsius)  High heat capacity (good coolant)  Takes a large amount of energy for water to evaporate (moderates climate)  Universal solvent  Water expands when it freezes (helps form soil)  pH = 7  Adhesion/cohesion

Core Case Study: Water Conflicts in the Middle East - A Preview of the Future  Many countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages (water stress). Figure 14-1

Water Conflicts in the Middle East: A Preview of the Future  Most water in this dry region comes from the Nile, Jordan or Tigris rivers.  Countries are in disagreement as to who has water rights.  Currently, there are 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 keeps us alive, moderates climate, sculpts the land, removes and dilutes wastes and pollutants, and moves continually through the hydrologic cycle.  Only about 0.02% of the earth’s water supply is available to us as liquid freshwater (97.4 % = oceans, 2.6% = fresh)

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL  Comparison of population sizes and shares of the world’s freshwater among the continents. Figure 14-2

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

Ground Water Terms  Recharge Area  Artesian Well  Aquifer  Zone of Saturation  Zone of Aeration  Water Table  Confined Aquifer  Unconfined Aquifer  Saltwater Intrustion

Fig. 14-3, p. 308 Unconfined Aquifer Recharge Area Precipitation Evaporation and transpirationEvaporation Confined Recharge Area Runoff Flowing artesian well Recharge Unconfined Aquifer Stream Well requiring a pump Infiltration Water table Lake Infiltration Unconfined aquifer Confined aquifer Confining impermeable rock layer Less permeable material such as clay

WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL  We currently use more than half of the world’s reliable runoff of surface water and could be using 70-90% by  About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to these sources.  Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and residences (10%) - average person uses 1280 gallons/day.

Water in the United States  Average precipitation (top) in relation to water-deficit regions and their proximity to metropolitan areas (bottom). Figure 14-4

Case Study: Freshwater Resources in the United States  17 western states by 2025 could face intense conflict over scarce water needed for urban growth, irrigation, recreation and wildlife. Figure 14-5

TOO LITTLE FRESHWATER  Causes: dry climate, drought, dessication, water stress  Riparian Rights (east coast)  Common Law Rights (western)

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

Fig. 14-7, p. 313 Trade-Offs Withdrawing Groundwater AdvantagesDisadvantages Useful for drinking and irrigation Aquifer depletion from overpumping Available year- round Sinking of land (subsidence) from overpumping Exists almost everywhere Polluted aquifers for decades or centuries Renewable if not overpumped or contaminated Saltwater intrusion into drinking water supplies near coastal areas Reduced water flows into surface waters No evaporation losses Cheaper to extract than most surface waters Increased cost and contamination from deeper wells

Groundwater Depletion: A Growing Problem  The Ogallala, the world’s largest aquifer, is most of the red area in the center (Midwest).  Areas of greatest aquifer depletion from groundwater overdraft in the continental U.S. Figure 14-8

Other Effects of Groundwater Overpumping  Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater. Figure 14-11

Other Effects of Groundwater Overpumping  Sinkholes form when the roof of an underground cavern collapses after being drained of groundwater. Figure 14-10

Groundwater Pumping in Saudi Arabia (1986 – 2004)  Irrigation systems from the nonrenewable aquifer appear as green dots. Brown dots are wells that have gone dry. Figure 14-9

Fig , p. 316 Solutions Groundwater Depletion PreventionControl 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 Do not grow water- intensive crops in dry areas Set and enforce minimum stream flow levels

USING DAMS AND RESERVOIRS TO SUPPLY MORE WATER  Large dams and reservoirs can produce cheap electricity, reduce downstream flooding, and provide year-round water for irrigating cropland, but they also displace people and disrupt aquatic systems.

Fig a, p. 317 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) Downstream flooding is reduced Migration and spawning of some fish are disrupted

Fig b, p. 317 Powerlines Reservoir Dam Powerhouse Intake Turbine

The Colorado River Basin  The area drained by this basin is equal to more than one- twelfth of the land area of the lower 48 states. Figure 14-14

Case Study: China’s Three Gorges Dam  There is a debate over whether the advantages of the world’s largest dam and reservoir will outweigh its disadvantages. The dam will be 2 kilometers long. The dam will be 2 kilometers long. The electric output will be that of 18 large coal- burning or nuclear power plants. The electric output will be that of 18 large coal- burning or nuclear power plants. It will facilitate ship travel reducing transportation costs. It will facilitate ship travel reducing transportation costs. Dam will displace 1.2 million people. Dam will displace 1.2 million people. Dam is built over seismatic fault and already has small cracks. Dam is built over seismatic fault and already has small cracks.

Dam Removal  Some dams are being removed for ecological reasons and because they have outlived their usefulness. In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S. In 1998 the U.S. Army Corps of Engineers announced that it would no longer build large dams and diversion projects in the U.S. The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams. Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment. Removing dams can reestablish ecosystems, but can also re-release toxicants into the environment.

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 has created a major ecological, economic, and health disaster. About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared. About 85% of the wetlands have been eliminated and roughly 50% of the local bird and mammal species have disappeared. Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct. Since 1961, the sea’s salinity has tripled and the water has dropped by 22 meters most likely causing 20 of the 24 native fish species to go extinct.

Options to Increase Freshwater  Distillation: heating saltwater until it evaporates, leaves behind water in solid form (lots of salty waste).  Reverse osmosis: uses high pressure to force saltwater through a membrane filter  Cloud seeding  Towing Icebergs  Water Baggies

INCREASING WATER SUPPLIES BY WASTING LESS WATER  65-70% of the water people use throughout the world is lost through evaporation, leaks, and other losses  Water is underpriced through government subsidies  Drip irrigation  Center-pivot, low-pressure sprinklers  Xeriscaping

Fig , p. 325 Center pivot Drip irrigation 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. (efficiency 90–95%) (efficiency 80%–95%) Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Fig , p. 326 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 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 , p. 327 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 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

Solutions: Using Less Water to Remove Industrial and Household Wastes  Use nutrients in wastewater before treatment as soil fertilizer  Use waterless and odorless composting toilets that convert human fecal matter into a small amount of soil material.

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

Fig , p. 331 Solutions Reducing Flood Damage PreventionControl Preserve forests on watersheds Strengthen and deepen streams (channelization) Preserve and restore wetlands in floodplains Tax all development on floodplains Build levees or floodwalls along streams Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry, and recreation Build dams

SOLUTIONS: USING WATER MORE SUSTAINABLY  We can use water more sustainably by cutting waste, raising water prices, preserving forests and wetlands in water basins, and slowing population growth. Figure 14-25