Water Use and Management

WATER RESOURCES

• Water (all states) covers more than 70% of world’s surface.

Hydrologic Cycle

Hydrologic Cycle

• Solar energy drives the hydrologic cycle by evaporating surface water.– Evaporation - Changing liquid to a vapor below

its boiling point.– Sublimation - Changing water between solid

and gaseous states without ever becoming liquid.

Hydrologic Cycle

• Humidity - Amount of water vapor in the air.– Saturation Point - When a volume of air contains

as much water vapor as it can hold at a given temperature.

– Relative Humidity - Amount of water vapor in the air expressed as a percentage of the maximum amount that can be held at that temperature.

Hydrologic Cycle

• Dew Point - Temperature at which condensation occurs for a given amount of water.– Cloud Condensation Nuclei (CCN) - Tiny

particles that facilitate condensation.• Smoke, dust, sea salt, spores, sulfate aerosols

(remember Air Pollutants)

Major Water Compartments• Glaciers, Ice, and Snow

– 2.6% of world’s water is classified fresh.

– 0.5 % is groundwater

• 0.014% readily accessible freshwater

(lakes, rivers, groundwater).

– As recently as 18,000 years ago, one-third of continental landmasses were covered by glacial ice sheets.

• Now, Antarctic glaciers contain nearly 85% of all ice in the world.

– Sea ice comes from ocean water, but salt is excluded during freezing.

• http://video.nationalgeographic.com/video/player/environment/going-green-environment/green-home-makeover/conserve-water-greenguide.html

• http://video.nationalgeographic.com/video/player/environment/going-green-environment/green-home-makeover/conserve-water-greenguide.html

MAJOR WATER COMPARTMENTSMAJOR WATER COMPARTMENTSOceans

– Together, oceans contain more than 97% of all liquid water in the world.• Contain 90% of world’s living biomass.• Moderate earth’s temperature.

– Average residence time of water in the ocean is between 100 days to 3,000 years. (range)

Major Water Compartments

• Groundwater- water below the water table– Second largest reservoir of fresh water.

• Infiltration - Process of water percolating through the soil and into fractures and permeable rocks.

– Zone of Aeration - Upper soil layers that hold both air and water.

– Zone of Saturation - Lower soil layers where all spaces are filled with water.

• Water Table - Top of Zone of Sat.

GroundwaterGroundwater

Groundwater• Aquifers - Porous layers of sand, gravel, or rock

lying below the water table. (can be drained)– Artesian - Pressurized aquifer intersects the surface.

(Water flows without pumping)

• Recharge Zone - Area where water infiltrates into an aquifer.– Recharge rate is often very slow.

• Presently, groundwater is being removed faster than it can be replenished in many areas.

Groundwater & Aquifers

Balancing the Water Budget• Oceans account for 86% of total evaporation.

– Ninety percent of water evaporated from the ocean falls back on ocean as rain.

• Remaining 10% is carried by prevailing winds over continents.

WORLD'S TEN LARGEST LAKES (IN TERMS OF SURFACE AREA)

Name and location Area mi 2 Area km 2 Volume km 3

Caspian Sea (saltwater) Turkmenistan, Kazakhstan, Russia, Azerbaijan, Iran

149,200 386,400 78,200

Lake Superior (largest freshwater lake) United States, Canada

31,700 82,100 12,230

Lake Victoria Kenya, Tanzania, Uganda

26,828 69,485 2,700

Lake Huron United States, Canada

23,000 59,600 3,537

Lake Michigan United States 22,300 57,800 4,920

Lake Tanganyika Burundi, Tanzania, Zaire, Zambia

12,700 32,900 18,900

Lake Baikal Russia 12,200 31,500 22,995

Great Bear Lake Northwest Territories, Canada

12,028 31,153 2,381

Lake Malawi (formerly Lake Nyasa) Malawi, Mozambique, Tanzania

11,430 29,604 6,141

Aral Sea (saltwater) Kazakhstan, Uzbekistan

11,200 (in 1998), was 26,500 (in

1960)

28,687 (in 1998), was 68,000 (in

1960)

181 (in 1989), was 1,040 (in

1960)

Read more: http://www.waterencyclopedia.com/Hy-La/Lake-Formation.html#ixzz0UIb52wv1

Major Water Compartments

• Wetlands– Play a vital role in hydrologic cycle.

• Lush plant growth stabilizes soil and retards surface runoff, allowing more aquifer infiltration.

– Disturbance reduces natural water-absorbing capacity, resulting in floods and erosion in wet periods, and less water flow the rest of the year.

Major Water Compartments

• The Atmosphere– Among the smallest water reservoirs.

• Contains < 0.001% of total water supply.• Has most rapid turnover rate.• Provides mechanism for distributing fresh

water over landmasses and replenishing terrestrial reservoirs.

WATER AVAILABILITY AND USEWATER AVAILABILITY AND USE

• Renewable Water Supplies– Made up of surface runoff and infiltration into

accessible freshwater aquifers.• About two-thirds of water carried in rivers and

streams annually occurs in seasonal floods too large or violent to be stored effectively for human use.

– Readily accessible, renewable supplies are 400,000 gal /person/year.

Rainfall and Topography

• Mountains act as cloud formers and rain catchers.– Air sweeps up the windward side of a

mountain, pressure decreases, and the air cools.• Eventually saturation point is reached, and moisture

in the air condenses.– Rain falls on the mountaintop.

• Cool, dry air descends and warms, absorbing moisture from other sources. (Rain Shadow)

Rainfall and TopographyMount Waialeale – Kaua’i in Hawaii

Drought Cycles• Every continent has regions of scarce rainfall due

to topographic effects or wind currents.– Water shortages have most severe effect in semiarid

zones where moisture availability is the critical factor in plant and animal distributions.

• US seems to have 30 year drought cycle.

– Climatic changes such as global warming may alter cycles.

Types of Water Use

• Withdrawal - Total amount of water taken from a source.

• Consumption - Fraction of withdrawn water made unavailable for other purposes (Not returned to its source).– Degradation - Change in water quality due to

contamination making it unsuitable for desired use.

Types of Water Use

• Worldwide, humans withdraw about 10% of total annual renewable supply.– Many societies have always treated water as an

inexhaustible resource.• Natural cleansing and renewing functions of

hydrologic cycle do not work properly if systems are overloaded or damaged.

Quantities of Water Used

• Human water use has been increasing about twice as fast as population growth over the past century.– Average amount of withdrawn worldwide is about

170,544 gal/person/year.– Annual renewable water supply in US amounts to

an average of 2.4 million gallons/person/year.• Now withdraw one-fifth of this amount.

Global Water Use Growth

Water Use By Sector

• Worldwide, agriculture claims about 69% of total water withdrawal.– In many developing countries, agricultural

water use is extremely inefficient and highly consumptive.

• Worldwide, industry accounts for about 25% of all water use.– Cooling water for power plants is single largest

industrial use.

FRESHWATER SHORTAGES

• Estimated 1.5 billion people lack access to an adequate supply of drinking water.– Nearly 3 billion lack acceptable sanitation.

• A country where consumption exceeds more than 20% of available, renewable supply is considered vulnerable to water stress.– Globally, water supplies are abundant, but, along

with capital resources, are unevenly distributed.

A Precious Resource

• Currently, 45 countries, most in Africa or Middle East, are considered to have serious water stress, and cannot meet the minimum essential water requirements of their citizens.– More than two-thirds of world’s households

have to retrieve water from outside the home.• Sanitation levels decline when water is expensive.

Depleting Groundwater

• Groundwater is the source of nearly 40% of fresh water in the US.– On a local level, withdrawing water faster than

it can be replenished leads to a cone of depression in the water table,

• On a broader scale, heavy pumping can deplete an aquifer.

– Ogallala Aquifer

• Mining non-renewable resource.

Depleting GroundwaterDepleting Groundwater

• Withdrawing large amounts of groundwater in a small area causes porous formations to collapse, resulting in subsidence.– Sinkholes form when an underground channel

or cavern collapses.– Saltwater intrusion can occur along coastlines

where overuse of freshwater reservoirs draws the water table low enough to allow saltwater to intrude.

Saltwater IntrusionSaltwater Intrusion

INCREASING WATER SUPPLIES

• Seeding Clouds – Condensation Nuclei (addition of chemicals)

• Towing Icebergs– Cost

• Desalination – Most common methods are distillation and

reverse osmosis.• Three to four times more expensive than most

other sources.

Increasing Water Supplies• Dams, Reservoirs, Canals and Aqueducts

– Common to trap excess water in areas of excess and transfer it to areas of deficit.

– Environmental Costs• Upsets natural balance of water systems.

– Ecosystem Losses• Loss of wildlife habitat.

– Reservoir Size

– Water Quality

Dams, Reservoirs, Canals and Aqueducts

– Displacement of People• Three Gorges Dams in China will force relocation of over a

million people. (Yangtze’s River)

– Evaporation, Leakage, Siltation• Evaporative losses from Lake Mead and Lake Powell on the

Colorado River is about 1km3 per year (264 billion gallons).

• Dams slow water flow, allowing silt (nutrients) to drop out.

– Loss of Free-Flowing Rivers

WATER MANAGEMENT AND CONSERVATION

• Watershed Management– Watershed - All the land drained by a stream or

river.• Retaining vegetation and ground cover helps retard

rainwater and lessens downstream flooding.

– Additionally, retaining crop residue on fields reduces flooding and minimizing plowing and forest cutting on steep slopes protects watersheds.

Typical US Household Water Use

Price Mechanisms and Water Policy

• Through most of US history, water policies have generally worked against conservation.– In well-watered eastern states, water policy was

based on riparian use rights.– In drier western regions where water is often a

limiting resource, water law is based primarily on prior appropriation rights.

• Fosters “Use it or Lose it” policies.

Price Mechanisms and Water Policy

• In most federal reclamation projects, customers were only charged for immediate costs of water delivery.– Dam and distribution system costs were

subsidized.

• Growing recognition that water is a precious and finite resource has changed policies and encouraged conservation across the US.

GIARDIA - bacterial

                    

          

Cholera - bacteria