Water

Water distribution

Water covers ¾ of the earth’s surface Less then 1% is available for human use 99% is found in the oceans or locked away in ice

caps

Water distribution

A. Oceans

1. contain 97 % of the worlds water cover about 70% of the earths surface.

2. Water has high heat capacity this means that water temperature raises and fall

slowly. This helps to moderate global climate

3. Oceans support many plant and animal resources

Water distribution

B. Surface water

1. Rivers important source of freshwater

2. Rivers carry runoff back to the ocean and maintain water balance

3. Lakes are important for supplying domestic water to many communities

Water distribution

C. Ground water is found in porous rocks and in the soil below the earth’s surface.

1. Ground water contains more then 30X the water in the worlds rivers and lakes.

2. Above the saturated zone of ground water is a small amount of water held in the soil. Feeds the plant life

3. Two threats to ground water are overuse and pollution

4. the replacement rate of ground water is slow so pollution affects it for a long time.

Problems of fresh water

1. Personal use accounts for 1/10 th of the renewable supply

2. Agriculture accounts for 70% of the worlds water usage.

3. Industry uses ¼ of the supply – production of energy from nuclear and fossil fuel power plants are the greatest industry users.

Water cycle

Water cycle

Water from the air condenses and falls in the form of precipitation. This water can run off and end up in lakes and streams This water can be absorbed into the soil and end up as ground

water Ground water will eventually end up in the ocean Water from the surface is returned to the atmosphere by

evaporation and transpiration Transpiration is when water is evaporated from the leaves of

plants.

Water management

Two approaches 1. increase water supplies by building dams 2. using water more effectively and conserving

water supplies Dams and Reservoirs 1. Dams store or impound water that can be used for

irrigation, drinking and home use, generating electricity, and industry

Dams and reservoirs

2. Dams interrupt natural stream flow and disrupts natural fish migration and alter water temperature and oxygen content.

3. There is a large amount of water loss from reservoirs are tremendous. Large amounts evaporate and seep into the ground. This loss of water leaves dissolved salt behind. The water left becomes saltier.

4. Particles are moving slower then in a river and build up and deposit

Water diversion projects

Channeling water form water-rich to water-poor areas. Systems of channels or aqueducts are used in California

Managing ground water 1. We are pulling water out faster then it can be

replaced. Ex. Ogallala aquifer that extends from Texas to the Dakotas

Managing ground water

2. This removal of water causes subsidence. Empty space is created where water has been removed and pressure causes the land to lower.

3. Once these areas collapse the water holding capacity of the aquifer is reduced.