WATER RESOURCES AP ENVIRONMENTAL SCIENCE The amount of water in the earth is constant

WATER RESOURCESWATER RESOURCESAP ENVIRONMENTAL SCIENCEAP ENVIRONMENTAL SCIENCE

The amount of water in the earth is constantThe amount of water in the earth is constant

Imporantant ResourceImporantant Resource• Water is essential and Water is essential and

maintains all life and maintains all life and ecosystemsecosystems

• It regulates the It regulates the temperature of the temperature of the planetplanet

• Redistributes heatRedistributes heat• Cycles essential Cycles essential

nutrients through land, nutrients through land, air and all living things.air and all living things.

Renewable ResourceRenewable Resource• Fresh water is a renewable resource because of the

hydrologic cycle which returns water to both surface and groundwater sources from the atmosphere.

Earth’s Earth’s Distribution Distribution

of Waterof Water

Natural Capital: Surface WaterNatural Capital: Surface Water• Fresh water that

exists above ground– Streams– Rivers– Ponds– Lakes– Wetlands

• Watershed– Area of land drained

by a river system– Drainage basin

Natural Capital: Surface WaterNatural Capital: Surface Water

• Almost ¾ of all water used in the U.S. comes from surface water and is used for electric power generation, municipalities, industrial use, and irrigation

South Platte River, Colorado

Natural Capital: Surface WaterNatural Capital: Surface Water

• Productivity classification

– Oligotrophic• Low nutrients • High oxygen

– Eutrophic• High nutrients• Low oxygen

• Eutrophication usually results from human-caused excessive nutrient pollution.

Natural Capital: WetlandsNatural Capital: Wetlands• Surface water systems

in which the soil is saturated with water

• Generally feature shallow standing water with lots of vegetation

• Marsh• Swamp• Bog

Natural Capital: WetlandsNatural Capital: Wetlands• Vernal Pool

– Seasonal wetlands containing water only at a specific time of the year.

• Wetlands are extremely valuable as habitat for wildlife

• Wetlands provide important ecosystem services

– Slowing runoff– Reducing flooding– Recharging aquifers– Filtering pollutants

Natural Capital: WetlandsNatural Capital: Wetlands• Extensive damage of

wetlands has occurred throughout the U.S.

• Less than half of all wetlands remain

• Ramsar Convention on Wetlands (1971)

– Seeks protection of wetlands worldwide

Natural Capital: Natural Capital: Ground Water SystemsGround Water Systems

• Water beneath Earth’s surface, held within the pores of soil and/or rock.

• Account for ¼ of all water used in the U.S.

• Supplies almost ½ of all drinking water

• Important source of irrigation for Midwest


Evaporation and transpiration

Evaporation

Stream

InfiltrationWater tableInfiltration

Unconfined aquifer

Confined aquifer

Lake

Well requiring a pump

Flowingartesian well

Runoff

Precipitation

ConfinedRecharge Area

Aquifer

Less permeable materialsuch as clay Confirming permeable rock layer

Natural Capital: Natural Capital: Ground Water SystemsGround Water Systems• Aquifers

• Underground reservoir contained in porous, sponge-like formations of rock, sand or gravel.

• Largest know aquifer is the Ogallala, located under 8 U.S. Great Plains states


• unconfined aquifer unconfined aquifer is an aquifer with a permeable water table.

• confined aquifer confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure.

• Some aquifers are replenished by precipitation; others are not.


• As aquifers are withdrawn, they recharge VERY slowly; average rates are only about 1 m per day.


• Water Table• The upper limit of

groundwater held in an aquifer

• Drops when aquifers are overdrawn

• Result= becomes more difficult and expensive to extract.


• In parts of Mexico, India, China and many Asian and M.E. nations, water tables are falling 3-10 feet per year.

• In coastal areas, saltwater can intrude, making the water undrinkable and land can subside, creating sinkholes

SustainabilitySustainability• ONLY if water is used and

managed sustainably can water be realized as a renewable resource.

• Currently, in many industrial nations, concerns over water quantity dominate

• In developing countries, concerns over both water quantity and quality persist

Where Does It Rain?Where Does It Rain?• Humans are not distributed across the globe in Humans are not distributed across the globe in

accordance with water availability.accordance with water availability.

Where Does It Rain?Where Does It Rain?• A growing number of heavily populated countries are A growing number of heavily populated countries are

located in arid landslocated in arid lands

Global Water ConflictsGlobal Water Conflicts

Two main factors for water shortage: dry climate and too many people. Many people live in hydro poverty – can’t afford clean water.

Sharing Water Resources Sharing Water Resources Among Countries Among Countries

Potable WaterPotable Water

Safe Drinking Water•Nearly 1 billion people do not have access to safe drinking water•80% of human illness result from poor drinking water•Increasing populations put additional stress on water supplies

What is the Trend?What is the Trend?• Over the last centuryOver the last century

• Human population has Human population has increased 3xincreased 3x

• Global water withdrawal has Global water withdrawal has increased 7xincreased 7x

• Per capita water withdrawal Per capita water withdrawal has increased 4xhas increased 4x

• About one-sixth of the About one-sixth of the world’s people don’t have world’s people don’t have easy access to safe watereasy access to safe water

• Most water resources are Most water resources are owned by governments and owned by governments and are managed as publicly are managed as publicly owned resourcesowned resources

Usage?Usage?

Annual Precipitation of the Continental U.S.Annual Precipitation of the Continental U.S.

• A person needs about 1 gallon water/day for hydration

• In the US each person uses about 188 gallons/day

• An additional 657 gallons/person/day are used for irrigation, industrial use.

• Total per capita use is about 2000 gal/person/day

• US has highest per capita water withdrawal, followed by Canada, Australia, Russia, Japan

Too Little WaterToo Little Water

• Problems in the • West

• Dry climate• Drought • Desiccation

Acute shortage

Adequate supply

Shortage

Metropolitan regions with population greater than 1 million

US has plenty of water.Much of it is in the wrongplace at the wrong time.Most serious problems are flooding, pollution, and occasional urban shortages

Too Little WaterToo Little Water

• Growing Problem

Population GrowthPopulation Growth• Supply & demand are in

growing conflict – – supply is finite– water management driven

by values and needs• In the western US, irrigation

makes up 85% of all water use– 50% to grow food for livestock– 35% to grow crops

• Not sustainable…cost of water is heavily subsidized by the federal government

Supply and DemandSupply and Demand• Agriculture uses

approximately 70% of the Earth’s annual fresh water withdrawn from our streams and rivers

Supply and DemandSupply and Demand• Amount of land currently being irrigated has

doubled in the last 50 years to meet the demand for food.

Supply and DemandSupply and Demand

• Most irrigation remains highly inefficient

• Crops end up using only 40% of the water applied by “flood and furrow” methods

Supply and DemandSupply and Demand• Over-irrigation

leads to waterlogging and the salinization of agricultural lands

• World-wide, about 15-35% of water withdrawals for irrigation are thought to be unsustainable.

Supply and DemandSupply and Demand

• Industry– Accounts for

approximately 20% of Earth’s annual fresh water use

• Residential– Accounts for

approximately 10% of Earth’s fresh water use.

Bottled WaterBottled Water• Bottled drinking water

production now represents a significant groundwater extraction and depletion problem

• Nestle, Pepsi-Cola, Coca-Cola have begun extracting ground water, bottling and selling it for a profit, and then moving on , leaving the community from which the water was taken with a degraded resource base.

Bottled WaterBottled Water• Bottled water exerts

substantial ecological impact because it is heavily packaged and transported long distanced using fossil fuels.

• Bottled water is not demonstrably safer or healthier than tap water

• In fact, often the source is not as strictly regulated as drinking water by the EPA

Supply and DemandSupply and Demand• Change in land use changes permeability• Areas with 15 to 75 percent impervious surface are Areas with 15 to 75 percent impervious surface are

characterized as moderately developed.characterized as moderately developed.• Areas with greater than 75 percent impervious surface are Areas with greater than 75 percent impervious surface are

considered urban or highly developed. considered urban or highly developed.

Supply and DemandSupply and Demand• Areas with greater than Areas with greater than

10% impervious surface 10% impervious surface have been proven to have have been proven to have a negative affect on a negative affect on groundwater and storm groundwater and storm water.water.

Water RightsWater Rights• Water collectively belongs Water collectively belongs

to the publicto the public– Cannot be owned by Cannot be owned by

individualsindividuals• Individuals or groups may Individuals or groups may

be granted rights to use be granted rights to use waterwater– Legal authorization to Legal authorization to

use a predefined quantity use a predefined quantity of public water for a of public water for a designated purpose.designated purpose.

• Irrigation, domestic Irrigation, domestic water supply, power water supply, power generationgeneration

Water RightsWater Rights• State law requires certain

users of public waters to receive approval from the state prior to using water.

• Any use of surface water which began after 1917 requires a water-right permit.

• Withdrawals of underground water from 1945 requires a water-right permit.

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WATER RESOURCES AP ENVIRONMENTAL SCIENCE The amount of water in the earth is constant