Ground water & the major waterways

Ground water is water stored under the surface of the Earth. Convey to the students that ground water sometimes takes hundreds of years to accumulate. A good example of this occurs in the Sahara Desert in Africa, where ground water has accumulated for thousands of years and is still being used for drinking and irrigation. Ground water is stored in the ground below us, where different types of rocks can act as reservoirs. Sand or sandstone is the best material for a reservoir and forms extensive aquifers underground, but not all sands are created equal, as students will find out in lab.

Filtering water through different porous substances cleans water naturally in the ground. Substances like charcoal and diatomite (white powder that people put in pools), help to filter small particles that may be suspended in water.

The ground on which we live, is made up of many layers of different types of rocks. Water can move into the tiny pores within the rocks or soil. As they move, the different rocks can trap the particles in the pores. Some rocks have more pores than other rocks and can act as a reservoir of water or an aquifer. Some municipal water supplies depend on ground water for a source of drinking water. Filtering techniques are used in municipal water supplies. Water from a reservoir is cleaned through a combination of filtering and chemical processes.

Watersheds refer to how water moves through a given area.  Water may be pure H2O when it starts the process from precipitation, but gains dissolved substances as it moves throughout the system.  For instance, as water erodes through rocks, it dissolves the minerals that make up rocks. 

Water is a universal solvent, which basically means many compounds and elements can dissolve within the matrix of water.  The substances are dissolved usually in the “ionic” form which are easy for organisms to take it out of the water.  For instances, dissolved oxygen is easily dissolved at the atmosphere water interface, which is used by the fauna that lives in the water. 

Every place where humans live have to consider their water supply.  Throughout history, humans that were able to maintain water supplies were the most successful.  The Romans are noted for their ability to keep a  water supply through the use of aqueducts.  Large droughts in Egypt probably lead to part of its downfall as a great civilization.

Cities that sustain large populations, like New York City, have to think about where their water comes from and how to maintain a flow.  City and state officials have to think about how to maintain the water supply in times of drought and even have to think about what happens when there is too much water.

Water issues in the United States are very complicated and different from state to state.  For instance, most of California would be a desert if different cities didn’t buy water rights from different areas.  Los Angeles, for example,  owns water rights as far as Nevada, and San Francisco owns rights in the Sierra Nevada.

California's agricultural business is greatly dependent upon water. Without water, the Central Valley, Sacramento Valley, and San Fernando Valley would not be centers of agriculture.  Most of these areas would be deserts if it wasn't for water especially in the southern portion of the state.  California's fight for water is very important, especially when the distribution of water is so uneven.  The northern part of the state naturally has water, but the southern half does not get enough rainfall.  The California Aqueduct, one of the largest man-made structures in the world, brings northern water to the south.  The southern part of the state has also "trapped" part of the Colorado River through the Colorado aqueduct.  The capture of water by southern California has a very intriguing history especially in the early 1900's. 

California needs its reservoirs and dams to secure that water will always be available.  Drought conditions are common throughout history in California.  To insure the availability of water California had developed a system of reservoirs and dams.