Chapter 14 Water. WATER’S IMPORTANCE, AVAILABILITY, AND RENEWAL covers 71% of the Earth’s surface regulates Earth’s climate dilutes wastes sculpts.

Chapter 14Chapter 14

WaterWater

WATER’S IMPORTANCE, AVAILABILITY, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAND RENEWAL

covers 71% of covers 71% of the Earth’s the Earth’s surfacesurface

regulates regulates Earth’s climateEarth’s climate

dilutes wastesdilutes wastes sculpts earth’s sculpts earth’s

surface,surface, major habitatmajor habitat

SupplySupply 97% in 97% in oceansoceans

3% fresh 3% fresh waterwater

2.997% in 2.997% in ice caps ice caps glaciersglaciers

.003% .003% available available to usto us

Watersheds - drainage Watersheds - drainage basinsbasins

areas of land that drain into areas of land that drain into bodies of surface waterbodies of surface water

water flowing off land into water flowing off land into these bodies is called surface these bodies is called surface runoffrunoff

Fig. 14-3, p. 308

Unconfined Aquifer Recharge Area

Precipitation Evaporation and transpiration Evaporation

Confined Recharge Area

Runoff

Flowing artesian well

Recharge Recharge Unconfined Unconfined AquiferAquifer

Stream Well requiring a pumpInfiltration Water

table LakeInfiltration

Unconfined aquifer

Confined aquiferConfining impermeable rock layer Confining impermeable rock layer

Less permeable Less permeable material such as claymaterial such as clay

Water TableWater Table

upper surface of zone of upper surface of zone of saturation poorly demarcated saturation poorly demarcated between saturated soil and rock between saturated soil and rock and unsaturated soil and rockand unsaturated soil and rock

falls in dry weather and rises in falls in dry weather and rises in wet weatherwet weather

Cone of depressionCone of depression withdrawal rate of withdrawal rate of aquifer exceed natural aquifer exceed natural recharge rate , recharge rate ,

water table around water table around withdrawal well loweredwithdrawal well lowered

creates a waterless creates a waterless volumevolume

any pollution any pollution discharged onto land discharged onto land above will be pulled above will be pulled directly into welldirectly into well

WATER’S IMPORTANCE, WATER’S IMPORTANCE, AVAILABILITY, AND RENEWALAVAILABILITY, AND RENEWAL

We currently use more than half of the We currently use more than half of the world’s reliable runoff of surface water and world’s reliable runoff of surface water and could be using 70-90% by 2025.could be using 70-90% by 2025.

About 70% of the water we withdraw from About 70% of the water we withdraw from rivers, lakes, and aquifers is not returned to rivers, lakes, and aquifers is not returned to these sources.these sources.

Irrigation is the biggest user of water (70%), Irrigation is the biggest user of water (70%), followed by industries (20%) and cities and followed by industries (20%) and cities and residences (10%).residences (10%).

WITHDRAWING GROUNDWATER WITHDRAWING GROUNDWATER TO INCREASE SUPPLIESTO INCREASE SUPPLIES

Most aquifers are renewable resources Most aquifers are renewable resources unless water is removed faster than it is unless water is removed faster than it is replenished or if they are contaminated.replenished or if they are contaminated.

Groundwater depletion is a growing problem Groundwater depletion is a growing problem mostly from irrigation.mostly from irrigation. At least one-fourth of the farms in India are being At least one-fourth of the farms in India are being

irrigated from overpumped aquifers.irrigated from overpumped aquifers.

Other Effects of Groundwater Other Effects of Groundwater OverpumpingOverpumping

Groundwater Groundwater overpumping can overpumping can cause land to sink, cause land to sink, and contaminate and contaminate freshwater aquifers freshwater aquifers near coastal areas near coastal areas with saltwater.with saltwater.

Figure 14-11Figure 14-11

Other Effects of Groundwater Other Effects of Groundwater OverpumpingOverpumping

Sinkholes form when Sinkholes form when the roof of an the roof of an underground cavern underground cavern collapses after being collapses after being drained of drained of groundwater.groundwater.

Figure 14-10Figure 14-10

Figure 14-13Figure 14-13

Case Study: The Colorado Basin – an Case Study: The Colorado Basin – an Overtapped ResourceOvertapped Resource

Lake Powell, is Lake Powell, is the second the second largest reservoir largest reservoir in the U.S.in the U.S.

It hosts one of It hosts one of the hydroelectric the hydroelectric plants located on plants located on the Colorado the Colorado River.River.

Figure 14-15Figure 14-15

The Colorado River BasinThe Colorado River Basin

The area The area drained by this drained by this basin is equal to basin is equal to more than one-more than one-twelfth of the twelfth of the land area of the land area of the lower 48 states.lower 48 states.

Figure 14-14Figure 14-14

Central Arizona Project CanalCentral Arizona Project Canal

The project was designed to provide water to The project was designed to provide water to nearly one million acres of Indian and non-nearly one million acres of Indian and non-Indian irrigated agricultural land areas in Indian irrigated agricultural land areas in Maricopa, Pinal, and Pima Counties Maricopa, Pinal, and Pima Counties

The CAP is a system of canals, pumping The CAP is a system of canals, pumping stations and storage facilities that brings stations and storage facilities that brings water 336 miles from the Colorado River at water 336 miles from the Colorado River at Lake Havasu east to the Phoenix area and Lake Havasu east to the Phoenix area and then south to the Tucson area. Fourteen then south to the Tucson area. Fourteen pumping plants lift water 2,400 feet in pumping plants lift water 2,400 feet in elevation to the terminus. elevation to the terminus.

Case Study: Case Study: China’s Three Gorges DamChina’s Three Gorges Dam

There is a debate over whether the There is a debate over whether the advantages of the world’s largest dam and advantages of the world’s largest dam and reservoir will outweigh its disadvantages.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-The electric output will be that of 18 large coal-

burning or nuclear power plants.burning or nuclear power plants. It will facilitate ship travel reducing transportation It will facilitate ship travel reducing transportation

costs.costs. Dam will displace 1.2 million people.Dam will displace 1.2 million people. Dam is built over seismatic fault and already has Dam is built over seismatic fault and already has

small cracks. small cracks.

Dam RemovalDam Removal

Some dams are being removed for ecological Some dams are being removed for ecological reasons and because they have outlived their reasons and because they have outlived their usefulness.usefulness. In 1998 the U.S. Army Corps of Engineers In 1998 the U.S. Army Corps of Engineers

announced that it would no longer build large announced that it would no longer build large dams and diversion projects in the U.S.dams and diversion projects in the U.S.

The Federal Energy Regulatory Commission has The Federal Energy Regulatory Commission has approved the removal of nearly 500 dams.approved the removal of nearly 500 dams.

Removing dams can reestablish ecosystems, but Removing dams can reestablish ecosystems, but can also re-release toxicants into the can also re-release toxicants into the environment.environment.

INCREASING WATER SUPPLIES BY INCREASING WATER SUPPLIES BY WASTING LESS WATERWASTING LESS WATER

We waste about two-thirds of the water we We waste about two-thirds of the water we use, but we could cut this waste to 15%.use, but we could cut this waste to 15%. 65-70% of the water people use throughout the 65-70% of the water people use throughout the

world is lost through evaporation, leaks, and world is lost through evaporation, leaks, and other losses.other losses.

Water is underpriced through government Water is underpriced through government subsidies.subsidies.

The lack of government subsidies for improving The lack of government subsidies for improving the efficiency of water use contributes to water the efficiency of water use contributes to water waste.waste.

Fig. 14-18, p. 325

Center pivotCenter pivot

Drip irrigationDrip irrigation

Gravity flowGravity 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.

TOO MUCH WATERTOO MUCH WATER Heavy rainfall, rapid snowmelt, removal of Heavy rainfall, rapid snowmelt, removal of

vegetation, and destruction of wetlands vegetation, and destruction of wetlands cause flooding.cause flooding.

Floodplains, which usually include highly Floodplains, which usually include highly productive wetlands, help provide natural productive wetlands, help provide natural flood and erosion control, maintain high water flood and erosion control, maintain high water quality, and recharge groundwater.quality, and recharge groundwater.

To minimize floods, rivers have been To minimize floods, rivers have been narrowed with levees and walls, and narrowed with levees and walls, and dammed to store water.dammed to store water.

TOO MUCH WATERTOO MUCH WATER

Comparison of St. Louis, Missouri under Comparison of St. Louis, Missouri under normal conditions (1988) and after severe normal conditions (1988) and after severe flooding (1993).flooding (1993).

Figure 14-22Figure 14-22