Post on 06-Jan-2016
description
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%
Water’s Importance , Availability and Renewal
Groundwater:
Zone of saturation:
Water table:
Aquifers:
Natural recharge:
Water’s Importance , Availability and Renewal
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.
Water’s Importance , Availability and Renewal
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.
Figure 14-6Figure 14-6
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.
Figure 14-8Figure 14-8
Other Effects of Groundwater Overpumping
Groundwater overpumping can cause land to sink, and contaminate freshwater aquifers near coastal areas with saltwater.
Figure 14-11Figure 14-11
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.
Figure 14-14Figure 14-14
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.
Figure 14-17Figure 14-17
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.
Increasing Water Supplies by Wasting Less Water
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.
Increasing Water Supplies by Wasting Less Water
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.
Figure 14-23Figure 14-23
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.
Figure 14-25Figure 14-25