Water Chapter 15. Water Wars Water shortage Growing population Poor irrigation efficiency Economic competition- importing more grain to reduce need for.

Water

Chapter 15

Water Wars

Water shortage Growing population Poor irrigation efficiency

Economic competition- importing more grain to reduce need for irrigation water or work out water-sharing agreements with other countries

Unique Properties of Water

Strong hydrogen bonds Liquid over wide temperature range High heat capacity – changes temperature

slowly (moderates climate, used as coolant for car engine & power plants)

Large amount of energy needed to evaporate – heat is then released during condensation (helps distribute heat & determine climate zones; evaporation/sweating = cooling process)

Dissolves many substances- dissolves nutrients in living tissue, flush waste out of tissues, all-purpose cleanser, helps remove/dilute water-soluble waste

Filters out UV radiation that would harm aquatic organisms

Bonds – allow capillary action – water can move upward through plants

Expands when frozen= ice floats; prevents lakes & streams from freezing solid

Available Freshwater

Only 0.014% is available for useh

Water Cycle

Surface runoff- water flowing off the land into bodies of surface water

Reliable runoff- amount of run-off that we can generally count on as a stable source of water

Watershed (drainage basin)- region from which surface water drains into a river, lake, wetland, or other body of water

Groundwater- water stored in spaces in soil & rock

Zone of aeration- close to surface; pore space contains mixture of air & water

Zone of saturation- lower layers of soil where pore space is filled with water

Water table- top of zone of saturation Aquifer- (deep) porous, water-saturated

layers of sand, gravel, or bedrock through which groundwater flows

Natural recharge- natural replenishment of an aquifer by precipitation, which percolates downward through soil & rock

Shortages result from: Removing groundwater faster than it is

replenished Some aquifers receive little, if any recharge

Water Use

Withdrawal- total amount of water removed from lake, river, or aquifer for any purpose

Consumptive water use- withdrawn water is not available for reuse in basin due to losses like evaporation, seepage into ground, transportation to another area, or contamination

Water Use

Population- up 3x Global water withdrawal- up 7x Per capita withdrawal- up 4x

Reliable surface runoff used- 34% Used by 2025- 70% (90% if per capita rises

too)

Irrigation- 70% Industry- 20% Residences & cities- 10%

Eastern U.S.

Major water use- energy production, cooling, & manufacturing

Problems- flooding, occasional urban shortages, pollution

Western U.S.

Major water use- irrigation

Problems- shortage of runoff, low precipitation / high evaporation, recurring prolonged drought

Causes of Water Scarcity

Dry climate Drought- prolonged period with 70% less

precipitation & higher than normal evaporation

Dessication- drying of exposed soil due to deforestation or overgrazing

Water stress- low per capita availability due to high population relying on limited runoff

Increase Freshwater Supply

Build dams & reservoirs to store runoff Bring in surface water from another area Desalinization Reduce water waste Import food to reduce water use in crops &

cattle Withdraw groundwater

Government Ownership

- Poor management & efficiency

+ Strict government oversight

+ Equal access & fair rates

Private Ownership

+ Funds & management expertise

+ Improved efficiency, good job

- No rate control

- Profitable

- Sold as a luxary, not basic need

Large lossesof water throughevaporation

Flooded landdestroys forestsor cropland anddisplaces people

Downstreamflooding is reduced

Downstreamcropland andestuaries aredeprived ofnutrient-rich silt

Reservoir isuseful forrecreationand fishing

Can producecheap electricity(hydropower)

Migration andspawning ofsome fish aredisrupted

Provides waterfor year-roundirrigation ofcropland

Figure 15-9Page 313

Colorado River Dams

+ Provides electricity from numerous hydroelectric plants

+ Provides water for 7 states+ Multibillion dollar recreational industry

(whitewater rafting, boating, fishing, camping, hiking)

- Arid area- Legal pacts allocating water supply for US &

Mexico- River water rarely makes it to Guld of

California

- Threatens aquatic spawning

- Destroys estuaries

- Increases saltwater contaminated coastal aquifers

Figure 15-11Page 315

Trade-Offs

China’s Three Gorges Dam

Advantages Disadvantages

Will generate about 10%of China’s electricity

Reduces dependence on coal

Reduces air pollution

Reduces CO2 emissions

Reduces chances ofdownstream floodingfor 15 million people

Reduces river sittingbelow dam by eroded soil

Increases irrigation waterfor cropland belowdam

Floods large areas of cropland and forests

Displaces 1.9 million people

Increases water pollutionbecause of reduced water flow

Reduces deposits of nutrient-rich sediments below dam

Increases saltwater Introduced into drinking water near mouth of river because of decreased water flow

Disrupts spawning andmigration of some fish below dam

High cost

Aral Sea Water Transfer Project

Shrinking of Aral Sea Regional ecological, economic, health

disaster Salinity 3x higher Surface area down 58% 83% water loss Feeder rivers reduced to trickles Eliminates wetlands Birds & mammal species disappeared

Extinction of 20 (of 24) native fish species Salt dust settles on wildlife, crops, & other

vegetation

California Water Transfer Project

NORTH Degrade Sacramento

River Threatens fisheries Reduces flushing of

San Francisco Bay pollutants

Water sent South is wasted

SOUTH Need more water to

grow crops Lakes shrink = reduced

populations of ducks, gulls, & wading birds

James Bay in Canada

- 600 dams & dikes that will reverse or alter flow of 19 giant rivers

- Will flood boreal forests & tundra

- Displace of indigenous Cree & Inuits

+ Hydroelectric power

Figure 15-15Page 319

Trade-Offs

Withdrawing Groundwater

Advantages Disadvantages

Good source of water fordrinking and irrigation

Available year-round

Exists almost everywhere

Renewable if not over-pumped or contaminated

No evaporation losses

Cheaper to extract than most surface waters

Aquifier depletion from over-pumping

Sinking of land (subsidence)when water removed

Polluted aquifiers unusablefor decades or centuries

Saltwater intrusion intodrinking water supplies nearcoastal areas

Reduced water flows intostreams, lakes, estuaries, and wetlands

Increased cost, energy use,and contamination fromdeeper wells

Excessive Withdrawal

Unsustainable water mining Limits future food production Increases gap between rich & poor areas Must drill deeper wells, buy larger pumps, &

use more electricity Causes sinkholes

Saltwater Intrusion

Movement of salt water into freshwater aquifers in coastal & inland areas as groundwater is withdrawn faster than it is recharged by precipitation

Groundwater becomes unusable

Ogallala Aquifer

+ Transformed vast areas of arid prairie into productive agricultural land

- Slows recharge rate

- Aquifer is thinner for southern region

- Government subsidies increased crop production & increases depletion of aquifer

Figure 15-18Page 320

Solutions

Groundwater Depletion

Prevention Control

Waste less water

Subsidize waterconservation

Ban new wells in aquifiers near surface waters

Buy and retire ground-water withdrawal rights in critical areas

Do not grow water-intensive crops in dry areas

Reduce birth rates

Raise price of water todiscourage waste

Tax water pumped from Wells near surface water

Set and enforce minimum stream flow levels

Deep Aquifer Concerns:

Little known about geological & ecological impacts of using these aquifers

No international water treaties govern the rights to & ownership of water that underlies several countries

Desalinization

- High cost

- Large energy requirements

- Large amounts of briny waste water

- Dumping of waste increases salinity of ocean water (food resources & aquatic life threatened)

+ Make ocean water or brackish water usable

Seeding Clouds

Does not work well in very dry areas No scientific evidence of success Introduces large amounts of chemicals into

soil & water systems (harms people, wildlife, & agricultural productivity)

Ownership of cloud water

Iceberg Towing

Unsure methods Cost

Probably neither (iceberg towing or cloud seeding) would provide significant amounts of freshwater

Wasted Water

65-70% of world water is wasted Could be reduced to 15% Causes: Underpricing- government subsidies for

irrigation water, electricity, & diesel fuel for farmers to pump water at below-market price

Lack of government subsidies for improving efficiency of water use

Irrigation Systems

Center pivot- uses pump to spray water on crops 80% efficient Uses 25% less water

Drip irrigation- microirrigation- above or below ground pipes or tubes deliver water to individual plant roots 90-95% efficient

Gravity flow- water flow into ditches from aqueduct or nearby river 60-80% efficient

Gravity Flow(efficiency 60% and 80% with

surge valves)

Water usually comes from an aqueduct system or a nearby river.

Drip Irrigation(efficiency 90-95%)

Above- or below-ground pipes or tubes deliver water to

individual plant roots.

Center Pivot(efficiency 80% with low-

pressure sprinkler and 90–95% with

LEPA sprinkler)

Water usually pumped from underground and sprayed from mobile boom with sprinklers.

Figure 15-20Page 324

Figure 15-21Page 324

Solutions

Reducing Irrigation Water Waste

•Lining canals bring water to irrigation ditches

•Leveling fields with lasers

•Irrigating at night to reduce evaporation

•Using soil and satellite sensorsand 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 crops varieties

•Irrigating with treated urban waste water

•Importing water-intensive crops and meat

Figure 15-22Page 325

Reducing Water Waste

Solutions

•Redesign manufacturing processes

•Landscape yards with plants that require little water

•Use drip irrigation

•Fix water leaks

•Use water meters and charge for all municipal water use

•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

Reducing Water Used to Remove Waste Use pollution prevention & waste reduction to

decrease waste production Ban toxic wastes in municipal sewer system Waterless composting toilet Nutrient-rich sludge returned to soil as

fertilizer New sewage treatment methods that recycle

nutrients in organic waste material

Floods

+ Fertile soils

+ Ample water for irrigation

+ Rivers for transportation & recreation

+ Flat land suitable for crops, buildings, highways, & railroads

- Removal of water-absorbing vegetation

Increasing Flood Damage

Removal of water-absorbing vegetation Draining wetlands Living on floodplains Pavement & buildings

Bangladesh

Straighten & deep streams Build levees or floodwalls Build dams Preserve existing wetlands & restore

degraded wetlands Identify & manage flood-prone areas Think carefully about where we live

Figure 15-26Page 329

• 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

• Raising water prices

• Wasting less water

• Decreasing government subsides for supplying water

• Increasing government subsides for reducing water waste

• Slowing population growth

Solutions

Sustainable Water Use

Figure 15-27Page 330

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

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

• Repair water leaks.

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

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

• 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.

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

• Use drip irrigation and mulch for gardens and flowerbeds.

• Use recycled (gray) water for watering lawns and houseplants and for washing cars.

What Can You Do?

Water Use and Waste