Chapter 9 * Distribution and usability of fresh water * 70% of earth is covered in water, but 97% of that is salt * Remaining freshwater (<.5% salt), 22% is underground, and 77% is frozen (<1% fresh water bodies) * 2.78% Freshwater, 97% found in ocean as saltwater * ¼ of all freshwater underground * ¾ aboveground but mostly in ice and glaciers (not very usable) * Very little resides in lakes, streams, rivers, wetlands * Groundwater structure and Use * Groundwater exists in permeable layers of rock called aquifers. These allow us to get usable ground water * Unconfined aquifers are aquifers that water can easily flow in and out of * Easily recharged from above * Confined aquifers are aquifers that are surrounded by an impermeable layer * Under high pressure and can create artesian wells * Water table is the uppermost limit of saturated rock. Separates zone of aeration from zone of saturation * Zone of aeration = pore spaces are partly filled with water * Zone of saturation = spaces are filled with water * Groundwater recharge zone is where water gets added to an aquifer (harder in confined aquifers) * Springs are where ground water reaches the surface. Naturally clean * Wells are holes dug into the groundwater (cone of depression)

* Problems with Depleting Groundwater * Saltwater intrusion- when the pumping of fresh water out of a well is faster than the recharge. Near coastal areas this can cause salt water to infiltrate the aquifer. * Sinkholes * Reduction of water in nearby streams/lakes/etc

* Surface Water Use, dikes, dams, aqueducts and examples * Surface water is fresh water that exists above ground (1%) * Much farming takes place near rivers because of water supply and floodplain make for nutrient rich plains *