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Mrs. Sealy - APES BLACK TURKEY SEA GEORGIA ARMENIA AZERBAIJAN TURKMENISTAN CASPIAN SEA MEDITERRANEAN SEA LEBANON WEST BANK GAZA SYRIA IRAN IRAQ JORDAN EGYPT OMAN KUWAIT Aswan High Dam Lake Nasser SAUDI ARABIA BAHRAIN QATAR UNITED ARAB EMIRATES SUDAN OMAN YEMEN SOMALIA ETHIOPIA Fig. 13.1, p. 294 How much freshwater is available and where is it? • 97.4% of water is in the ocean, 2.6% is freshwater and of that amount, Most is locked in icecaps leaving .014% available for use Freshwater Readily accessible freshwater Groundwater 0.592% Biota 0.0001% Lakes 0.007% Rivers 0.0001% 0.014% Ice caps and glaciers 1.984% Soil moisture 0.005% Atmospheric water vapor 0.001% Fig. 13.2, p. 296 United States Power cooling 38% China Agriculture 41% Industry 11% Public 10% Agriculture 87% Public 6% Industry 7% Fig. 13.5, p. 298 5,500 Water use (cubic kilometers per year) 5,000 Total use 4,500 4,000 3,500 3,000 2,500 2,000 Agricultural use 1,500 Industrial use 1,000 Domestic use 500 1900 1920 1940 1960 Year 1980 2000 Fig. 13.4, p. 298 1 automobile 400,000 liters (106,000 gallons) 1 kilogram cotton 10,500 liters (2,400 gallons) 1 kilogram aluminum 9,000 liters (2,800 gallons) 1 kilogram grain-fed beef 7,000 liters (1,900 gallons) 1 kilogram rice 1 kilogram corn 1 kilogram paper 1 kilogram steel 5,000 liters (1,300 gallons) 1,500 liters (400 gallons) 880 liters (230 gallons) 220 liters (60 gallons) Fig. 13.6, p. 298 What causes water shortages? • Dry climate • Drought • Desiccation • Water stress (low per capita availability due to population growth) • 30 countries containing 500,000 million people have chronic water shortages • There is enough water, but often it is wasted, polluted, is in areas where it is hard to get to. • Two-thirds of the world live in water poverty where they do not have water coming into the home. Competition for the World’s Water • Cities are outbidding farmers for water supplies from rivers and aquifers • Some countries are importing grain as a way to reduce their water needs • More crops are being used for biofuels increasing water demand. Average annual precipitation (centimeters) 0-25 0-25 25-50 25-50 50-75 50-75 Fig. 13.7a, p. 299 Acute shortage Adequate supply Shortage Metropolitan regions with population greater than 1 million Fig. 13.8b, p. 299 Europe North America Asia Africa South America Stress High Australia None Fig. 13.8, p. 300 How can water supplies be increased? • • • • • Building dams and reserviors Importing water Withdrawing groundwater Desalination improved efficiency Dams and reservoirs • • • • • • Pros: Can capture and store water The water can be released as desired Control flooding downstream Supply irrigation water year around Provide electricity Large losses of water through evaporation Downstream cropland and estuaries are deprived of nutrient-rich silt Flooded land destroys forests or cropland and displaces people Downstream flooding is reduced Provides water for year-round irrigation of cropland Reservoir is useful for recreation and fishing Can produce cheap electricity (hydropower) Migration and spawning of some fish are disrupted Fig. 13.9, p. 301 • Cons: • Silting behind the dam robs the downstream of nutrients • Loss of silt destroys deltas • Causes flooding behind the dam • They can fall down • Disturbs species like salmon • Causes landslides and earthquakes Case Study: The Colorado River • Water laws in the Western United States are governed by prior appropriation: “First in time, first in right”, which means the first to use the water has the first rights. On the Colorado River the Indians and the Ranchers were the first. • The Colorado is divided into two parts: * Upper Basin: Wyoming, Utah, Colorado, New Mexico * Lower Basin: Arizona, Nevada and Case Study: The Colorado River • In 1922 water was allocated to these states by the Colorado River compact, in 1944 Mexico was allocated water • The problem was that the amount of water was overestimated by 33%, so when all the states start taking their water, there will not be enough IDAHO WYOMING Dam Aqueduct or canal Salt Lake City Grand Junction Upper Basin Denver Lower Basin UPPER BASIN UTAH COLORADO Lake Powell Grand Canyon Las Vegas Glen Canyon Dam NEW MEXICO Boulder City ARIZONA CALIFORNIA Los Angeles Albuquerque LOWER BASIN Palm Springs Phoenix San Diego Yuma Mexicali All-American Canal Golf of California Tucson 0 100 mi. 0 150 km Fig. 13.10, p. 304 MEXICO The Science of Groundwater • Groundwater: rain that infiltrates the ground and percolates downward through spaces in soil, water and rock • Below a certain level the spaces are completely filled with water, called the zone of saturation . The top of this zone is the water table. • Aquifer: porous layers of sand, gravel and rock through which water flows (from which water can be extracted). • Recharge rate: how fast an aquifer can refill. Can take thousands of years. Tapping Groundwater • • • • Pros: Supplies 50 % of drinking water Supplies 40% of irrigation Usually very high quality Tapping Groundwater • Aquifer depletion: currently US is withdrawing groundwater at 4x it’s replacement rate • Aquifer subsidence: sinking of land due to water removal • Salt water intrusion: removing too much groundwater causes salt water to seep into aquifers Flowing artesian well Unconfined Aquifer Recharge Area Evaporation and transpiration Well requiring a pump Precipitation Evaporation Confined Recharge Area Runoff Aquifer Infiltration Stream Water table Lake Infiltration Unconfined aquifer Less permeable material such as clay Confined aquifer Confining permeable rock layer Fig. 13.3, p. 297 Major irrigation well Well contaminated with saltwater Water table Sea Level Salt water Fresh groundwater aquifer Interface Interface Saltwater Intrusion Normal Interface Fig. 13.17, p. 308 Original water table Initial water table Cone of depression Lowered water table Fig. 13.15, p. 307 Groundwater Overdrafts: High Moderate Minor or none Fig. 13.16a, p. 308 Subsidence: High Moderate Minor or none Fig. 13.16b, p. 308 Case Study: Ogallala Aquifer • The Ogallala aquifer stretches from Texas north to North Dakota. It was deposited over several thousand years duirng the last ice age. It is the largest aquifer in North America. It is nonrenewable because it has a very slow recharge rate. One quarter of it will be depleted by 2020. This is because the farmers get tax breaks for depleting it. In the Midwest there is no such thing as water conservation. Less than 61 meters (200 ft) WYOMING SOUTH DAKOTA 61-183 meters (200-600 ft) More than 183 meters (600 ft) (as much as 370 meters or 1,200 ft. in places) NEBRASKA KANSAS COLORADO OKLAHOMA NEW MEXICO TEXAS Miles 0 100 0 160 Kilometers Fig. 13.18, p. 309 Water Transfer • Pros: • Using tunnels, aquaducts and pipes to transport water from watersheds to water poor areas • Allows for year-around irrigation of cropland in arid regions • Has allowed L.A. to become what it is (Owens Valley water transfer). Water Transfer • Robs other areas of water • Can be environmentally harmful to areas where the water is being removed • Threatens fisheries • Causes rivers to flow backwards • Takes away the flushing action of rivers • Lowers the level of inland seas and lakes • Causes inland seas to become more salty and produces salt rain from blowing salt • Hard on native species Areas already harmed: • Aral Sea in Russia • Mono Lake in California • Sacramento River delta KAZAKHSTAN 2000 ARAL SEA 1989 1960 UZBEKISTAN TURKMENISTAN Fig. 13.12, p. 305 CALIFORNIA NEVADA Shasta Lake Sacramento River Oroville Dam and Reservoir Feather River North Bay Aqueduct UTAH Lake Tahoe Sacramento San Francisco Fresno South Bay Aqueduct Hoover Dam and Reservoir (Lake Mead) Colorado River Los Angeles Aqueduct San Luis Dam and Reservoir ARIZONA California Aqueduct Colorado River Aqueduct Santa Barbara Central Arizona Project Los Angeles Salton Sea Phoenix San Diego Tucson Fig. 13.13, p. 306 MEXICO Desalination • Removing salt from ocean water by distillation or reverse osmosis • Problem is that it requires large amounts of energy and it is very expensive Improved Efficiency • 60-70% of water is wasted worldwide • Why is water wasted: * artificially low prices in the US * government subsidies * outdated laws governing water supplies * water management in watersheds is divided into too many different hands. Wasting Less Water in Irrigation • Currently we use flood irrigation or gravity flow, which wastes 50% of water • Drip irrigation delivers water directly to plants with a 80-90% efficiency • Center-pivot-mobile boom moves over crops 70-80% efficient Gravity Flow Drip Irrigation Center Pivot (efficiency 60% and 80% with surge valves) (efficiency 90–95%) (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Water usually comes from an aqueduct system or a nearby river. Above- or below-ground pipes or tubes deliver water to individual plant roots. Water usually pumped from underground and sprayed from mobile boom with sprinklers. Fig. 13.19, p. 311 • Lining canals bringing water to irrigation ditches • Leveling fields with lasers • Irrigating at night to reduce evaporation • Using soil and satellite sensors and computer systems to monitor soil moisture and add water only when necessary • Polyculture • Organic farming • Growing water efficient crops using drought-resistant and salt-tolerant crop varieties • Irrigating with treated urban waste water • Importing water intensive crops and meat Fig. 13.20, p. 313 Wasting Less in Industry • Recycling water in the manufacturing process • Many companies already do this because it saves them money and they do not get government kickbacks on water like farmers do • Also companies have to pay for the amount of stuff that goes down the sewer Wasting Less in Businesses and Homes • Low flush toilets • Low flow shower heads • Xeriscaping • Fix leaky pipes • Reusing gray water in homes and to water lawns Too much water-Floods • Floodplain: the natural overflow area of a river, these are very productive areas with nutrient rich soils • Floods are natural thing- they enrich the soil, recharge groundwater and refill wetlands • Humans make flooding worse by removing vegetation, draining wetlands and living on floodplains Reservoir Dam Levee Floodplain Flood wall Fig. 13.22, p. 314 Oxygen released by vegetation Diverse ecological habitat Evaporation increases Trees reduce soil erosion from heavy rain and wind Steady river flow Agricultural land Leaf litter improves soil fertility Tree roots stabilize soil and aid water flow Forested Hillside Vegetation releases water slowly and reduces flooding Fig. 13.24a, p. 316 Tree plantation Evapotranspiration decreases Roads destabilize hillsides Ranching accelerates soil erosion by water and wind Winds remove fragile topsoil Agriculture land is flooded and silted up Gullies and landslides Heavy rain leaches nutrients from soil and erodes topsoil After Deforestation Silt from erosion blocks rivers and reservoirs and causes flooding downstream Rapid runoff causes flooding Fig. 13.24b, p. 316 Extremely severe Very severe Moderately severe Somewhat severe Fig. 13.25, p. 317 Not severe • Not depleting aquifers • Preserving ecological health of aquatic systems • Preserving water quality • Integrated watershed management • Agreements among regions and countries sharing surface water resources • Outside party mediation of water disputes between nations • Marketing of water rights • Wasting less water • Decreasing government subsides for supplying water • Increasing government subsides for reducing water waste • Slowing population growth Fig. 13.26, p. 317