apes ch 14

APES Ch 14

Water

Water’s Importance , Availability and Renewal You are made up of 60% water. Water is used in the production of food and building supplies. Water helps moderate climate, sculpt earths surface and dilutes

pollution Water is a

Global health issue- lack of water or sanitation systems is the single largest cause of illness.

Children’s issue- water is essential to healthy development Economic issue – water is a key to poverty reduction, food production

and energy production Women’s issue- in developing countries water is found and carried by

the women. National and global security issue- tension increases between nations

over limited or shared water Environmental issue – removal of water and pollution leads to

disappearing species, lower water tables, altered river flow, shrinking lakes, loss of wetlands, and declining water quality.

Water’s Importance , Availability and Renewal

Only 0.024% of the world’s water is available to us as liquid freshwater.

Hydrologic cycle recycles available water Can not recycle if water is overloaded with

pollutants or it is removed faster then the hydrologic cycle can process.

Some countries have too much water and some don’t have enough for their population.

Fig. 14-2, p. 307

ContinentPercent of world's water resources and population

Asia60.5%

36%

Africa10%

8%Europe

North and Central America 7.3%

South America and Caribbean 6.4%

26%

15%

5%Oceania

11.3%

0.5%

14%


Groundwater:

Zone of saturation:

Water table:

Aquifers:

Natural recharge:


Surface water:

Surface runoff:

Watershed (drainage basin):

There is a hydrological connection between surface and ground water. Most ground water makes its way into a lake, river or stream.

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’s Importance , Availability and Renewal 2/3 of surface runoff is lost by floods and is not available for human

use. 1/3 is reliable runoff:

Due to population growth we now withdraw 34% of reliable runoff and use another 20% to transport goods, dilute pollution and sustain fisheries and wildlife.

About 70% of the water we withdraw from rivers, lakes and aquifers is not returned to these sources (consumptive use). Water is not destroyed but renewed in a different part of the world.

It isn’t the amount we use but the rate at which we use it. Nonconsumptive use does not remove or only temporarily removes

water from its source.


Irrigation uses 70% of the water we withdraw. 85% is not returned to original source (lost

through evaporation and seepage into growndwater)

Industries uses 20%Cities and residence use 10%

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 14-5Figure 14-5

Too Little Freshwater

Main factors causing water scarcity: Dry climate, drought, too many people using

and wasting water, lack of $ to drill wells and build dams.

-“The fight for water will be more dramatic than the fight for oil in the long run. For oil we have substitutes, for water we have none.” –Gotthilf Hemple

-1 in every 6 people lack regular access to clean water.

Stress on the World’s River Basins

Comparison of the amount of water available with the amount used by humans.


Too Little Freshwater

Farmers and cities are competing for available water and farmers are losing because they require so much.

Plus, more crops are needed for the production of bio fuels.

How to get more water- 1. Withdrawing groundwater 2. Building dams and reservoirs 3. bring freshwater from other areas 4. Desalination

Withdrawing Groundwater to Increase Supplies

Most aquifer are renewable unless their water is depleted faster then it can renew itself.

Most aquifers are being depleted mainly for irrigation. Countries like India and China are rapidly

depleting groundwater and it will eventually run out causing famine and economic, political and social chaos.

Fig. 14-7, p. 313

Trade-Offs

Withdrawing Groundwater

Advantages Disadvantages

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.


Other Effects of Groundwater Overpumping

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


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

Main purpose is to capture and store runoff and release it as needed to control floods, generate electricity and to supply water for irrigation and for towns and cities.

There are more then 45,000 dams (22,000 in China).

Dams can reduce water downstream and prevent water from reaching the sea and altering the hydrologic cycle.

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

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.


Using Dams and Reservoirs

Case Study: China’s 3 Gorges Dam 1.4 miles long and cost $25 billion. Good news: electrical output of 18 coal plants (reduce

CO2), reduce floodwaters that kill 1,000s of people a year and it will allow cargo ships to travel further into China

Bad news: The huge reservoir behind the dam will displace 1.2 million people. It will flood 1,350 cities and towns

Mixed news: It is built on a seismic fault and could collapase during a earthquake and cause massive flooding. About 80 small cracks have already been found. Builders claim the dam can withstand a large earthquake.

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.

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.

Transferring Water

Advantages: brings water to dry areas for crops, grazing, and other business.

Disadvantages: encourages unsustainable use of water in areas where water is naturally available.

Transferring Water

Case Study: California Experience California Water Project uses dams, pumps and

aquaducts to transfer water from north California to south California

South wants more water from north to help grow more crops and support large cities. North claims that giving more water will degrade the rivers, threaten fisheries, and reduce flushing action that helps Sacramento Bay with pollutants.

Fig. 14-16, p. 321

CALIFORNIA

Sacramento River

North Bay Aqueduct

Lake Tahoe

San Francisco Sacramento

South Bay Aqueduct

Hoover Dam and Reservoir (Lake Mead)

NEVADA UTAH

Fresno

San Luis Dam and Reservoir Los Angeles

Aqueduct

Colorado River

California Aqueduct

Santa Barbara

Colorado River Aqueduct Central Arizona

Project

ARIZONA

Los Angeles

Salton Sea PhoenixSan Diego

Tucson

MEXICO

San Joaquin V

alley

Feather River

Shasta LakeOroville Dam and

Reservoir

Transferring Water

Case Study: The Aral Sea Disaster Aral Sea is shrinking b/c its waters have been

transferred to drier areas for irrigation Salinity has tripled, average level has dropped by 22

meters, lost 90% of its volume and has split in 2. 85% of wetlands have vanished and ½ of the bird

and mammal species have disappeared. Many more effects (pg 321-322)

Case Study: The Aral Sea Disaster

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


Desalination

Desalination:

Methods-

Distillation:

Reverse Osmosis:

Desalination

13,400 desalination plants mostly in countries that have dry, arid areas and are wealthy

2 major problems: High cost b/c it takes a lot of energy Produces large amount of briny waste water

very high in salt

Increasing Water Supplies by Wasting Less Water

Estimated that 65-70% of the water used is lost through evaporation, leaks, and other losses.

If we could reduce water loss by 15% we could meet the world’s water needs. Decrease burden on wastewater plants, reduce

the need for expensive dams and water transfer projects, slow depletion of groundwater aquifers.


2 Causes of water waste Main cause of water waste is we charge too

little for water. Gives users no financial incentive to safe water.

Lack of gov’t subsides for improving the efficiency of water use.


Solutions: More efficient and environmentally sound

irrigation technology Center-pivot, low pressure sprinkler: Low-energy, precision application sprinkler: Drip irrigation:

• DRiWATER:

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.

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

Fig. 14-21, 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

Too Much Water

Caused by heavy rain or rapid melting of snow.

To reduce flooding rivers have been narrowed and straightened, equipped with protective levees and walls and dammed.

Human activities that have increased floods include removal of water absorbing vegetation, draining and building on wetlands

TOO MUCH WATER

Human activities have contributed to flood deaths and damages.


Solutions: Using Water More Sustainably

Expand and improve monitoring of river flows, aquifer levels, sizes and recharge rate and watershed health.

Overhaul water policy to protect natural ecosystems that help store water, slow erosion, help groundwater recharge, provide flood control.

Regulate aquifer withdrawals Leave enough water in rivers to protect wildlife, ecological

processes and services Remove gov’t subsides that allow water to be underpriced and add

subsides that reward water conservation Switch to waste treatment plants that only accept non-toxic waste,

use less water to treat waste Get very serious about slowing global warming Slow population growth.

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.


apes ch 14

Documents

ground water

water scarcity

renewalsurface water

scarce water

childrens issue water

developing countries

lower water tables

declining water quality