Geos109 lect10 water

Water and Water Pollution

Case Study: Water Conflicts

Water shortages in the Middle East

Nile River

Jordan Basin

Tigris and Euphrates Rivers

Three Major River Basinsin the Middle East

Will We Have Enough Water?

We are using available freshwater unsustainably• wasting it • polluting it • charging too little for this irreplaceable natural

resource.

One of every six people do not have sufficient access to clean water, and this situation will almost certainly get worse.

Importance and Availability of Water

Why is water so important?

Earth as a watery world – 71%

Freshwater availability – 0.024%

Poorly managed resource

Hydrologic cycle

Water pollution

Confining impermeable rock layer

Less permeable material such as clay

Stream

Wellrequiringa pump Lake

Unconfined aquifer

Flowingartesian well

Runoff

ConfinedRechargeArea

Watertable

Confined aquifer

Infiltration

EvaporationEvaporation and transpiration

Infiltration

Unconfined Aquifer Recharge Area

Recharge Unconfined Aquifer

Precipitation

Groundwater

Zone of saturation

Water table

Aquifers

Natural recharge

Surface Water

Surface runoff

Watershed (drainage) basin

Reliable runoff – 1/3 of total

Runoff use• Domestic – 10%• Agriculture – 70%• Industrial use – 20%

Case Study: Freshwater Resources in the United States

Uneven distribution

Contamination

Eastern U.S.

Western U.S.

Groundwater withdrawal – 50%

Stepped Art

Average annual precipitation (centimeters)

Less than 41

41-81

81-122

More than 122

Acute shortage

Shortage

Adequate supply

Metropolitan regions with population greater than 1 million

Water Hot Spots in Western States

Freshwater Shortages

Causes of water scarcity• Dry climate• Too many people

1 of 6 people – no regular access to clean water• Over one billion have no access to improved

drinking water • According to the U.N. children's agency UNICEF,

polluted water and lack of basic sanitation claim the lives of over 1.5 million children every year, mostly from water-borne diseases.

While most people living in Western Europe can access safe water, only 50% of people living in Central Africa can do this. The largest population without access to safe tap water is in China (25%)

waterwiki.net/index.php/Unsafe_Water

Stress on World’s River Basins

How Can We Increase Water Supplies?

Groundwater used to supply cities and grow food is being pumped from aquifers in some areas faster than it is renewed by precipitation.

Using dams, reservoirs, and transport systems to transfer water to arid regions has increased water supplies in those areas, but has disrupted ecosystems and displaced people.

How Can We Increase Water Supplies?

We can convert salty ocean water to freshwater, but the cost is high, and the resulting salty brine must be disposed of without harming aquatic or terrestrial ecosystems.

Increasing Freshwater Supplies

Withdrawing groundwater

Dams and reservoirs

Transporting surface water

Desalination

Water conservation

Better use of natural hydrologic cycle

Aquifer Depletion from Groundwater Overdraft in the United States

Saltwater Intrusion intoCoastal Water Wells

Trade-offs of Large Dams and Reservoirs

California Water Project and Central Arizona Project

Aral Sea Disaster

Large-scale water transfers in dry central Asia

Salinity

Wetland destruction and wildlife

Fish extinctions and fishing

Aral Sea Disaster

Wind-blown salt

Water pollution

Climatic changes

Restoration efforts

Shrinking Aral Sea

Removing Salt from Seawater

Desalination

Distillation

Reverse osmosis

15,000 plants in 125 countries

Major Problems with Desalination

High cost Death of marine organisms Large quantity of brine wastes Future economics

Ashkelon Plant supplies 15%of Israel’s Householdswater needs-Largest plant in 2005

How Can We Use Water More Sustainably?

We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.

Reducing Water Waste (1)

Benefits of water conservation

Worldwide – 65-70% loss • Evaporation, leaks

Water prices, government subsides, waste

Reducing Water Waste (2)

Improve irrigation efficiency

Improve collection efficiency

Use less in homes and businesses

Major Irrigation Systems

Reducing Irrigation Water Waste

Reducing Water Waste

Sustainable Water Use

What Can You Do?

How Can We Reduce the Threat of Flooding?

We can improve flood control by protecting more wetlands and natural vegetation in watersheds and by not building in areas subject to frequent flooding.

Benefits of Floodplains (1)

Highly productive wetlands

Provide natural flood and erosion control

Maintain high water quality

Recharge groundwater

Benefits of Floodplains (2)

Fertile soils

Nearby rivers for use and recreation

Flatlands for urbanization and farming

Dangers of Floodplains and Floods

Deadly and destructive

Human activities worsen floods

Failing dams and water diversion

Hurricane Katrina and the Gulf Coast• Removal of coastal wetlands

Before and During a Flood inSt. Louis, Missouri

Case Study: Floodplains of Bangladesh

Dense population

Located on coastal floodplain

Moderate floods maintain fertile soil

Increase frequency of large floods

Development in the Himalayan foothills

Destruction of coastal wetlands

Hillside Before and After Deforestation

Reducing Flood Damage

How Can We Best Deal with Water Pollution? (1)

Streams can cleanse themselves of many pollutants if we do not overload them.

Preventing water pollution usually works better and costs less than trying to clean it up.

How Can We Best Deal with Water Pollution? (2)

Reducing water pollution requires preventing it, working with nature in treating sewage, cutting resource use and waste, reducing poverty, and slowing population growth.

Water Pollution Sources

Water pollution

Point sources• Discharge at specific locations• Easier to identify, monitor, regulate

Nonpoint sources• Runoff of chemicals and sediment• Agriculture• Control is difficult and expensive

Major Water Pollutants and Their Sources

Pollution in Streams

Lake Pollution (1)

Dilution less effective than with streams• Stratification• Low flow

Lakes are more vulnerable than streams

Eutrophication – natural aging process• Oligotrophic

Oligotrophic and Eutrophic Lakes

Groundwater Pollution (1)

Sources

Slow flow, dilution, dispersion

Low dissolved oxygen

Fewer bacteria

Cooler temperatures

Groundwater Pollution (2)

Longtime scale for natural cleansing• Degradable wastes – organic matter• Slowly degradable wastes – DDT• Nondegradable wastes – lead, arsenic, fluoride

Sources of Groundwater Pollution

Extent of Groundwater Pollution

Global scale – not much known

Monitoring is very expensive

Underground fuel tank leakage• MTBE

Arsenic

Protecting groundwater – prevention is best!

Preventing and Cleaning Up Groundwater Pollution

Ocean Pollution

Coastal areas – highly productive ecosystems• Occupied by 40% of population• Twice that population by 2050• About 80% marine pollution originates on land

Deep ocean waters• Some capacity to dilute, disperse, degrade

pollutants• Ocean dumping controversies• Assimilative capacity?

Coastal Water Pollution

Science Focus: Oxygen Depletion in the Northern Gulf of Mexico

Oil Pollution in Oceans

Crude and refined petroleum

Tanker accidents – Exxon Valdez

Urban and industrial runoff

Effects of Oil Pollution on Ocean Ecosystems

Volatile organic hydrocarbons• Kill larvae• Destroys natural insulation and buoyancy

Heavy oil• Sinks and kills bottom organisms• Coral reefs die

Oil Cleanup Methods

Current methods recover no more than 15%

Prevention is most effective method• Control runoff• Double haul tankers

Preventing and Cleaning Up Pollution in Coastal Waters

Preventing Nonpoint Source Pollution (1)

Mostly agricultural waste

Use vegetation to reduce soil erosion

Reduce fertilizer use

Preventing Nonpoint Source Pollution (2)

Use plant buffer zones around fields and animal feedlots

Keep feedlots away from slopes, surface water and flood zones

Integrated pest management

Laws for Reducing Point Source Pollution

Clean Water Act

Water Quality Act

Discharge trading controversies

Sewage Treatment Systems

Rural and suburban areas – septic tank

Urban areas – wastewater treatment plants• Primary treatment – physical process• Secondary treatment – biological process• Chlorination – bleaching and disinfection

Primary and Secondary Sewage Treatment

Improving Sewage Treatment

Systems that exclude hazardous waste

Nonhazardous waste substitutes

Composting toilet systems

Reducing Water Pollution from Point Sources in the U.S.

Impressive achievements

Bad news – 2006 survey• 45% of lakes and 40% of streams too polluted for

fishing and swimming• Runoff polluting 7 of 10 rivers• Fish caught in 1/4 of waterways unsafe to eat

Should the Clean Water Act be Strengthened?

Yes – environmentalists

No – farmers and developers

State and local officials want more discretion

Drinking Water Quality

Purification of urban drinking water

Developed versus developing countries

Is Bottled Water the Answer?

120 to 7,500 times the cost of tap water

About 1/4 is ordinary tap water

About 40% of bottled water contaminated

Water testing

Water purifiers

Methods for Preventing and Reducing Water Pollution

What Can We Do?