Water Resources

Water video questions How much fresh water on earth? How much in rivers, lakes, and streams? How much is used for growing food? How much water needed to produced a pound of beef? A cup of coffee? In US how much water is used for flushing toilet? How much water does the average American use per day? How many people today lack access to clean, safe water supply?

National Geographic http://www.youtube.com/watch?v=Fvkzjt3b-dU Why Care About Water http://www.youtube.com/watch?v=2pXuAw1bSQo Our Thirsty World

Water Resources Water is essential to life on Earth. Two kinds of water found on Earth: Salt water, the water in oceans, contains a higher concentration of dissolved salts. Fresh water, the water that people can drink, contains little salt.

The Water Cycle Water is a renewable resource because it is circulated in the water cycle. Water molecules travel between the earth’s surface and the atmosphere (evaporation, condensation, precipitation) Almost all the earth’s water is in the oceans. 97% of the earth’s water is salt water. Fresh water comes from rivers, lakes, and a zone beneath the soil.

The Water Cycle Evaporation: water rising to the atmosphere From where? Bodies of water: oceans, lakes, streams… From plants: transpiration

2. Condensation: water vapor forms drops 3. Precipitation: drops collide & form larger drops, then fall to the ground as rain or snow

4. Runoff: water running off mountains, hills etc… 5. Ground water: water in the ground makes its way to rivers, oceans…

Surface Water It’s fresh water. Found in lakes, rivers, streams, wetlands. Human societies developed around bodies of water. It provided drinking water, food (fish), water for agriculture, transportation, power for industry.

Surface Water

River Systems Streams form when rain water and melting snow travel down mountains, hills, plateaus, and plains. They form a network of water called a river systems. The Mississippi, Amazon, and Nile are huge river systems.

Mississippi River

Mississippi Delta

Amazon River Largest river system in the world.

Amazon River - largest

Nile River

Nile River

Watershed

Watersheds It’s the area of land that is drained by a river. Pollution anywhere in a watershed can pollute the river. The amount of water in a watershed depends on quantity of rain and melting snow. If the watershed shrinks the community (city, town, village) is affected.

Groundwater Water stored beneath the earth’s surface. Stored in sediment and rock formations. When it becomes full it is known as a water table. In wetlands the water table is near the surface. In deserts the water table is hundreds of meters below the earth’s surface.

Aquifer An underground formation containing groundwater. Consist of materials such as rock, sand, gravel. Water accumulates there. Aquifers are important for cities and agriculture.

Aquifer

Porosity and Permeability Porosity: amount of space between the particles that make up rock. The more porous a rock the more water it will hold. Permeability: ability of a rock or soil to allow water to flow through it. Granite and clay are impermeable. Sandstone, limestone, sand, gravel are permeable. The best aquifers form in permeable rock.

The Recharge Zone It’s the area of the Earth’s surface where water percolates (moves down) into an aquifer. If the recharge zone is polluted, the water entering an aquifer will be polluted. Cemented surfaces (parking lots, buildings) will decrease water trying to enter an aquifer. Aquifers can take tens of thousands of years to recharge.

Recharge Zone

Wells It’s a hole dug or drilled into the ground to reach groundwater. They need to be drilled below the water table.

Review What is the difference between fresh and salt water? What is the percentage of Earth that is covered with water? What is a river system? What is groundwater? What is an aquifer? What is the difference between permeability and porosity? What is a water recharge zone?