Chapter 14

Water

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. Figure 14-1

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.

WATER’S IMPORTANCE, AVAILABILITY, AND

RENEWAL Some precipitation infiltrates the

ground and is stored in soil and rock (groundwater).

Water that does not sink into the ground or evaporate into the air runs off (surface runoff) into bodies of water. The land from which the surface water

drains into a body of water is called its watershed or drainage basin.

Timber Stand

Forested Land

Cattle Farming

Agricultural Crops

Residential

IndustrialDam

Georgia’s Major Watersheds Do you see Atlanta?

Altamaha River Watershed

Ocmulgee

Using GIS to determine land

use in a watershed

Agricultural fields contribute to non-point

source pollution

Fig. 14-3, p. 308

Unconfined Aquifer Recharge Area

Precipitation Evaporation and transpiration Evaporation

Confined Recharge Area

Runoff

Flowing artesian well

Recharge Unconfined Aquifer

Stream Well requiring a pumpInfiltration Water

table LakeInfiltration

Unconfined aquifer

Confined aquiferConfining impermeable rock layer

Less permeable material such as clay

Artesian well

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 2025.

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%).

Agriculture34%

Industry55%

Municipal11%

US Groundwater Use

Global Water Use

TOO LITTLE FRESHWATER

About 41% of the world’s population lives in river basins that do not have enough freshwater.

Many parts of the world are experiencing: Rivers running dry. Lakes and seas shrinking. Falling water tables from 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

TOO LITTLE FRESHWATER

Cities are outbidding farmers for water supplies from rivers and aquifers.

Countries are importing grain as a way to reduce their water use.

More crops are being used to produce biofuels.

Our water options are: Get more water from aquifers and rivers,

desalinate ocean water, waste less water.

WITHDRAWING GROUNDWATER TO INCREASE SUPPLIES

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

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

are being irrigated from overpumped aquifers.

Light blue color indicates water – between the rocks and within the cracks of bedrock

What are ways we protect our water and what are ways we degrade our groundwater?

Why should we protect our

mountains?

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

Ogallala AquiferWorld’s largest ancient aquifer

Excessive irrigation in the mid-west has depleted the Ogallala Aquifer faster than

it can be replenished

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. 14-12, p. 316

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

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.

Hoover Dam

Fig. 14-13a, 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. 14-13b, p. 317

Powerlines

Reservoir

Dam

PowerhouseIntake

Turbine

Falling water spins the turbine connected to the

generator to create energy

Electricity turbines

inside the Hoover Dam

Case Study: The Colorado Basin – an Overtapped

Resource The Colorado River has so many dams

and withdrawals that it often does not reach the ocean. 14 major dams and reservoirs, and

canals. Water is mostly used in desert area of the

U.S. Provides electricity from hydroelectric

plants for 30 million people (1/10th of the U.S. population).

Case Study: The Colorado Basin – an Overtapped

Resource Lake Powell, is

the second largest reservoir in the U.S.

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

Figure 14-15

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

Fig. 14-14, p. 318

Dam

Aqueduct or canal

Upper Basin

LOWER BASIN

0 100 mi.

0 150 km

Lower BasinUPPER BASIN

IDAHO

WYOMING

Salt Lake City

Grand JunctionDenver

UTAH

NEVADACOLORADOLake

Powell

Las Vegas

Grand Canyon Glen

Canyon Dam

Boulder CityNEW MEXICO

ARIZONALos Angeles

Albuquerque

PhoenixSan Diego

MexicaliYuma

Tucson

All-American Canal Gulf of

CaliforniaMEXICO

CALIFORNIA

Palm Springs

Col

orad

o R

iver

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 is 2 kilometers long. The electric output will be that of 18 large

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

transportation costs. Dam will displace 1.2 million people. 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.

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

Removal of this dam in Washington will restore salmon runs

TRANSFERRING WATER FROM ONE PLACE TO ANOTHER

Transferring water can make unproductive areas more productive but can cause environmental harm. Promotes investment, jobs and strong

economy. It encourages unsustainable use of water

in areas water is not naturally supplied.

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

Satellite image: Colorado River

Aqueduct

Colorado River Aqueduct

Case Study: The Aral Sea Disaster

The Aral Sea was once the world’s fourth largest freshwater lake.

Figure 14-17

19892001

The disappearance of the Aral Sea over time

View from space

The diversion of water from

the Aral Sea has dried up

the fishing industry

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.

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.

DESALTING SEAWATER, SEEDING CLOUDS, AND TOWING ICEBERGS AND

GIANT BAGGIES Removing salt from seawater by

current methods is expensive and produces large amounts of salty wastewater that must be disposed of safely. Distillation: heating saltwater until it

evaporates, leaves behind salt 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 towing icebergs or huge bags filled with freshwater to dry coastal areas have all been proposed but are unlikely to provide significant amounts of freshwater.

Iceberg Towing

Source of freshwater

INCREASING WATER SUPPLIES BY WASTING LESS WATER

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

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

Water is underpriced through government subsidies.

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

INCREASING WATER SUPPLIES BY WASTING LESS WATER

Sixty percent of the world’s irrigation water is currently wasted, but improved irrigation techniques could cut this waste 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%.

Fig. 14-18, 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.

Center-pivot irrigation

Drip irrigation

Gravity flow irrigation

Gravity flow irrigation

Sprinkler system loosing a great deal of water due to

evaporation

Fig. 14-19, 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

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

Raising the Price of Water: A Key to Water Conservation

We can reduce water use and waste by raising the price of water while providing low lifeline rates for the poor. 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%.

Solutions: Using Less Water to Remove Industrial and

Household Wastes We can mimic the way nature

deals with wastes instead of using large amounts of high-quality water to wash away and dilute industrial and animal 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.

Waterless urinal

TOO MUCH WATER Heavy rainfall, rapid snowmelt,

removal of vegetation, and destruction of wetlands cause flooding.

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

To minimize floods, rivers have been narrowed with levees and walls, and dammed 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

Fig. 14-24, p. 331

Solutions

Reducing Flood Damage

Prevention Control

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

Fig. 14-25, p. 333

What Can You Do?Water Use and Waste

• Use water-saving toilets, showerheads, and faucet aerators.

• Shower instead of taking baths, and take short showers.

• Stop water leaks.

• Turn off sink faucets while brushing teeth, shaving, or washing.

• Flush toilets only when necessary.

• Wash only full loads of clothes or use the lowest water-level for smaller loads.

• Use recycled (gray) water for lawn, gardens, house plants, car washing.

• Wash a car from a bucket of soapy water, and use the hose for rinsing only.

• If you use a commercial car wash, try to find one that recycles its water.

• Replace your lawn with native plants that need little if any watering and decorative gravel or rocks.

• Water lawns and gardens in the early morning or evening.

• Sweep or blow off driveways instead of hosing off with water.

• Use drip irrigation and mulch for gardens and flowerbeds.