Water Resources

Global Distribution 71%of Earth’s surface is water 97% of Earth water is Salt water 77% of the fresh water is frozen

Surface Water Drinking water Water for crops Food Power for industry fish and shellfish Power for industry Transportation

Surface Water River system – streams form from falling rain, melting snow drains. As streams flow downhill they combine with other streams to form rivers. The more streams that flow into the river the larger the river. Watershed – the area of land that is drained by a river

Ground Water – water beneath Earth’s Surface Water table - level where rocks and soil are saturated with water. Level depends on the amount of rainfall or proximity to a large body of water.

Aquifers an underground formation that contains groundwater. Water table is the upper boundary. A Water table is a large space where water can pool, like caves or underground lakes.

Rocks contain small holes or pore spaces Porosity – the percentage of total volume of a rock that has spaces (pores). The more porous a rock is the more water it will hold Permeability – ability of the rock to let water flow through it. Gravel is very permeable, but clay and granite do not let water flow through so they are impermeable. Most productive aquifers usually form in permeable materials – sandstone, limestone, or layers of sand and gravel.

Recharge Zone – area of earth’s surface from which water percolates down into an aquifer. Size depends on permeability of surface above the aquifer. Buildings, parking lots, etc. are impermeable layers so communities have to take this into account when allowing building. Can take tens of thousands of years to recharge