Due on 4/21 1:00pm CST

Maoxiaoying

Chapter13.pdf

Home >Environmental science homework help >Due on 4/21 1:00pm CST

Environment Tenth Edition

Raven

Chapter 13

Water: A Limited Resource

Overview of Chapter 13

• Importance of Water

• Water Use and Resource Problems

• Water Problems in U.S. and Canada

• Global Water Problems

• Water Management

• Water Conservation

Water Scarcity

• Lack of adequate water o 663 million people worldwide (1

in 11 people) lack access to improved water source

o 40% of world’s population experiences scarcity

o Some need to purchase water from questionable sources

• New technology to help areas identify new water reserves o Funding these technologies

always an issue

Importance of Water

• Freshwater ~ 2.5% of water on Earth o Use is increasing

• Need water everyday for: o Cooking and washing

o Agriculture

o Manufacturing

o Mining

o Energy production

o Waste disposal

Properties of Water

• Composed of 2 Hydrogen and 1 oxygen

• Exists as solid, liquid, or gas • High heat capacity • Polar • Forms hydrogen bond

between 2 water molecules o H-bonds define water’s physical

properties

Chemical Composition of 1kg of Seawater

• Water is never completely pure in nature

• Content of seawater (left)

• Water dissolves many chemicals that can act as pollutants

• Climate change is reducing freshwater in ice caps

• How will this affect the composition of seawater?

Distribution of Water

• < 2.5% of water on Earth is freshwater o 2% of this in the form of ice

• Only ~ 0.5% of water on Earth is available freshwater

• Certain forms of freshwater are used preferentially

• Which of the categories shown is diminishing due to climate change?

Freshwater Terminology • Surface water

o Precipitation that remains on the surface and does not seep into soil

• Runoff o Movement of surface water to lakes, rivers, eventually to ocean

• Drainage basin (watershed) o Land area that delivers water into a stream or river system

• Groundwater o Freshwater under the Earth’s surface stored in aquifers

• Aquifer o Underground cavern and porous layer of sand, gravel, and rock in

which groundwater is stored

Watersheds • Also known as catchment basins, drainage basins

o Watersheds are essential for water access

Table 13.1 The World’s 10 Largest Watersheds

Watershed Region Area of Watershed (thousand square kilometre)(thousand square kilometre)

Amazon South America 6145

Congo Africa 3731

Nile Africa 3255

Mississippi North America 3202

Ob Asia 2972

Paraná South America 2583

Yenisey Asia 2554

Lena Asia 2307

Niger Africa 2262

Yangtze Asia 1722

Source: Water Resources of the World, World Resources Institute (2010).

Watersheds and Groundwater

• A water table is the upper surface of the saturated zone of groundwater

Water Use and Resource Problems

• Fall into Three Categories o Too much water

o Too little water

o Poor quality/contamination (addressed in Chapter 21)

Too Much Water

• Flooding o Both natural and human-induced

• Modern floods are highly destructive (property loss) o Removal of water-absorbing plant cover from soil

o Construction of buildings on floodplains

• Floodplain o Area bordering a river channel that has the potential to

flood

Pre-Urban vs. Urban Floodplains

Floodplains

• Area bordering a river channel that has potential to flood o We increasingly build on

floodplains

• Government restrictions on building o Levees can fail

• Rather than rebuild levees adjacent to rivers, experts suggest allowing some floodplains to flood

Flood Management with River Channels or Levees

Left: Traditional levees adjacent to channelized river

Right: Suggested levee style, set back from river

Mississippi: Floods of Summer 2011

• Heavy rains and abundant snowmelt high in Mississippi River watershed

• Mississippi R. has extensive flood control mechanisms o Many failures, but many floods

prevented

• Debate over the degree of river alteration and building in floodplain

• Alteration in precipitation with climate change?

Too Little Water

• Arid (deserts) or semiarid lands have frequent, prolonged droughts

• Problems: o Overdrawing water for

irrigation purposes

o Population growth

o Aquifer depletion • Subsidence

• Sinkholes

Saltwater Intrusion

• Problems (continued) o Saltwater Intrusion

• Why are an increasing number of regions likely to experience saltwater intrusion?

Water Problems in U.S. and Canada

• Overall, U.S. has a plentiful supply of freshwater

• Many areas have severe shortages o Geographical variations

o Seasonal variations

Surface Water Shortages

• Particularly severe in West and Southwest of U.S. o Water is diverted and

transported via aqueducts

o Arid or semiarid region

o Historically diverted water used for irrigation

• Now, used more for commercial and industrial purposes

Surface Water Shortage – Mono Lake

• Mono Lake is in eastern CA

• Rivers and streams that once fed this lake are diverted to Los Angeles (275mi away)

• Becoming highly saline

• Court ordered water diversion reduction allowing water level to rise steadily

• Droughts lowered water level again (2007-2016)

• Year of heavy rain and snow raised level (2017)

Colorado River Basin

• Provides water for 35-40 million people and irrigation

• Numerous dams for hydropower

• 1922 Colorado River Compact o Annual 7.5million acre-feet of water to

lower CO area, remainder to upper CO area

o Overestimation of annual flow

o Mexico receives some, but increasingly salty due to use

• Colorado River rarely reaches ocean – dries up

Colorado River and Climate Change

• Prediction that climate changes may reduce flow 10- 30% within 30 years

• May reduce Lake Mead level and affect Hoover Dam’s electrical output

• New turbines in Hoover Dam to work more efficiently under low flow (2014)

Groundwater Problems in U.S. and Canada

• Aquifer Depletion as half of U.S. uses groundwater for drinking

• 40% of irrigation from groundwater

• Many areas where removal has resulted in salt water intrusion

High Plains Aquifer (Largely Ogallala Aquifer)

• Largest groundwater deposit in world

• Water removed for agriculture as much as 40x faster than nature can replace it

• Water table lowered 250ft in places

• Uneconomical to pump in some areas o Revert to dryland farming or farmers

leaving

Global Water Problems

• Amount of freshwater on planet can meet human needs

o However, unevenly distributed and some places lack stable runoff

• Dependent on the amount from precipitation throughout year

• Problems relating to water:

o Weather and climate variation

o Need for clean, consistent drinking water

o Population growth

o Sharing water resources among countries

Water and Climate Change

• Climate change affects the type and distribution of precipitation

• Potential issues: o Reduced snowfall (or variable runoff) will impact water

resources downstream • Ex: Californian drought 2014-2015

o Sea level rise will cause saltwater intrusion into drinking water supplies

Drinking-Water Problems

• Many developing countries have insufficient water to meet drinking and household needs

• ~ 663 million people lack access to safe drinking water o ~ 80% of human illnesses due to poor water quality

• Population Growth o Increase in population means an increase in freshwater

requirements

o Limits drinking water available

o Limits water available for agriculture (food)

Global Water Stress

Source: F. Gassert, M. Luck, M. Landis, P. Reig, and T. Shiao. Aqueduct Global Maps 2.0.

Working Paper. Washington, DC: World Resources Institute (2013).

Sharing Water Resources among Countries

• Rhine River Basin (right) o 5 countries share basin

o Some countries upstream polluted river

o Countries downstream had to pay to clean the water before they could drink it

o Major chemical spill in Switzerland galvanized action (1986)

o Currently, very clean water

Aral Sea

• At one point, volume down 80% o Many health problems for those

living around it

• Water diversion for irrigation has caused Sea to become too saline

• Plans to improve Aral Sea faltered with breakup of Soviet Union

• Some basins improving o Some worsening

1976 2016

Water Conflicts (1 of 3)

Table 13.2 Some Historical and Recent Water Conflicts

Date Conflict Description

2500 B.C.E. Military tool King Urlama of Lagash diverts flow of water from rival kingdom Umma (Lagash and Umma were both kingdoms in what is now Iraq).

1187 C.E. Military tool Saladin defeats European Crusaders, in part by depriving them of access to water. This includes filling wells with debris and eliminating villages that could have supported the Crusaders.

1672 Military tool The Dutch breach their protective dikes to prevent Spanish armies from invading by land. Dikes around Amsterdam and other Dutch cities are designed both to keep out seawater in peacetime and deter potential invaders in times of war.

Water Conflicts (2 of 3)

[Table 13.2 continued]

Date Conflict Description

1850s Development dispute/terrorism

When a dam is built to provide water for factories in New Hampshire, locals who object to the effect on their water supplies attack the dam.

1907–1913 Terrorism/develop ment dispute

The aqueduct from Owens Valley to Los Angeles is bombed multiple times by people objecting to the large-scale shift in allocation of this water resource.

1969 Military target Israel attacks the East Ghor Canal in Jordan to prevent diversion of water from the Yarmouk River.

1991 Military target During the First Gulf War, Iraq destroys desalination facilities in Kuwait.

Water Conflicts (3 of 3)

[Table 13.2 continued]

Date Conflict Description

2003–2007 Military tool, target/terrorism

Wells in Sudan and Darfur are destroyed and poisoned as part of civil war–related violence.

2010 Development dispute

Water dispute between Pakistani tribes leads to more than 100 deaths.

2014 Terrorism Unidentified groups attack a Venezuelan water treatment plant, contaminating the local water supply with diesel fuel.

2015 Military target Russian Federation forces bomb an Aleppo (Syria) water treatment facility, cutting off the water supply for 3.5 million people.

Source: Peter H. Gleick (2011). Water Conflict Chronology. Pacific Institute for Studies in Development, Environment, and Security; additional updates from the Pacific Institute online chronology.

Water Management

• Water viewed differently from other natural resources o Water is transboundary resource

o Management challenges vary with surface water compared with groundwater

• Main goal of management: Provide sustainable supply of high-quality water

• Sustainable water use - use that does not harm essential functions of the hydrologic cycle or the ecosystems on which present and future humans depend

Managing Water with Dams and Reservoirs • Benefits:

o Ensure year-round supply of water with regulated flow

o Generate electricity

o Provide recreational activities

• Disadvantages o Alter the ecosystem

o Reduce sediment load

Glen Canyon Dam

• Dam on Colorado River in Grand Canyon National Park

• Powerful spring floods historically brought sediment, which created sandbar habitat o Essential for wildlife reproduction and habitat

Dam Resulted in Loss of Habitat

• Regulated flow detriment to physical habitat o Loss of sandbars, loss of habitat

Periodic Flooding to Restore Habitat

• To rectify, government started flooding the Grand Canyon periodically starting in 1996 o More frequent releases in recent years

Water Diversion Projects

• Water diverted to areas that are deficient

• Much of southern CA receives its water supply from diverted water from northern CA

• Controversial and expensive

Desalinization

• Removal of salt from ocean or brackish water

• Two methods: o Distillation - salt water is evaporated, and water vapor is

condensed into freshwater

o Reverse Osmosis- involves forcing salt water through a membrane permeable to water, but not salt

• Expensive, but becoming more economical due to technology and demand (high energy demand) o Huge industry in Africa and Middle East (where freshwater is

scarce)

Water Conservation

• Reducing agricultural water waste o Agriculture is very inefficient

with water

o Microirrigation - irrigation that conserves water by piping to crops through sealed systems (drip or trickle irrigation)

Innovation to Aid Water Conservation

• New technologies o Combination of low-energy precision application (LEPA)

irrigation and geographic information systems (GIS) • GIS uses signals from satellites to identify locations in need of water

• Water applied only where and when needed (estimated by GIS)

o Has helped areas in Texas in 8-fold reduction in water use

Reducing Industrial Water Waste

• Many power generators and industries use water (ex: turbines, paper and pulp production)

• Stricter laws provide incentives to conserve water

• Water scarcity encourages further industrial recycling

• Potential to conserve water is huge

• Jackson Family Wines (CA) – water recycling program to save 6 million gallons

1yr−

o Efforts to restore low-flow creeks and salmon populations (2015)

Recycling Municipal Water

• Gray Water o Can be used to flush

toilets, wash car, or water lawn

• Water saving household fixtures

• Government incentives

Practices to Conserve Water

• Install water-saving shower heads and faucets

• Install low-flush toilets

• Fix leaky fixtures

• Purchase high efficiency appliances

• Modify personal habits

• Use the dishwasher when full instead of washing by hand

• Outdoor xeriscaping

• Water accountability and pricing

Section 117 of the 1976 United States Act without the express written permission of the

Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up

copies for his/her own use only and not for distribution or resale. The Publisher assumes

no responsibility for errors, omissions, or damages, caused by the use of these programs

or from the use of the information contained herein.