Earth's Water Sources - PowerPoint PPT Presentation

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Earth's Water Sources

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  1. Earth’s Water Sources Water-The Source of Life

  2. Oceans Lakes Ground Water Distribution of Water Glaciers Rivers Water Cycle Credits Table of Contents

  3. Rivers What is a river? Where does the water come from? Why are rivers important? River Pollution River Pollution Control

  4. A river is nothing more than surface water finding its way over land from a higher altitude to a lower altitude, all due to gravity. When rain falls on the land, it either seeps into the ground or becomes runoff, which flows downhill into rivers and lakes, on its way towards the seas. In most landscapes the land is not perfectly flat -- it slopes downhill in some direction. Flowing water finds its way downhill initially as small creeks. As small creeks flow downhill they merge to form larger streams and rivers. Rivers eventually end up flowing into the oceans. What is a river?

  5. The water in a river doesn't all come from surface runoff. Rain falling on the land also seeps into the earth to form ground water. At a certain depth below the land surface, called the water table, the ground becomes saturated with water. If a river bank happens to cut into this saturated layer, as most rivers do, then water will seep out of the ground into the river. Ground-water seepage can sometimes be seen when a road is built through water-bearing layers, and even on a driveway! Saturated, water-bearing materials often exist in horizontal layers beneath the land surface. Since rivers, in time, may cut vertically into the ground as they flow, the water-bearing layers of rock can become exposed on the river banks. Thus, some of the water in rivers is attributed to flow coming out of the banks. This is why even during droughts there is usually some water in streams. Where does the water come from?

  6. Rivers are invaluable to not only people, but to life everywhere. Not only are rivers a great place for people to play, but people use river water for drinking-water supplies and irrigation water, to produce electricity, to flush away wastes (hopefully, but not always, treated wastes), to transport merchandise, and to obtain food. Rivers are major aquatic landscapes for all manners of plants and animals. Rivers even help keep the aquifers underground full of water by discharging water downward through their streambeds. And, we've already mentioned that the oceans stay full of water because rivers and runoff continually refreshes them. Importance of Rivers

  7. Pollution As the water runs off of the land and back to the oceans, it carries with it many substances that it picks up along its way. It could run through a pool of gasoline spilled at the pump, loose dirt from the construction site, or fertilizers from the golf course. Also many serious diseases, such as cholera, are caused by drinking water that contains parasitic microorganisms. Water containing large amounts of industrial waste or agricultural chemicals (e.g., pesticides) can also be toxic. All of these cause pollution in the marine environment; pollution that not even the most modern equipment can clean up.

  8. Pollution Control In response to this need for reliable supplies of clean and usable freshwater, governments at all levels have formed organizations and passed legislation to monitor, treat, and protect our water supplies. The Clean Water Act established the policy of contracting water-treatment facilities and implemented enforcement procedures to ensure that our water supplies would be kept clean for human use. Later, the Safe Drinking Water Act of 1974 established minimum federal public-health standards for the water supply. The policies and standards provided by these acts, together with a large body of legislation developed at the state and local levels, have helped to ensure that residents of almost every part of the United States have access to a safe, usable supply of water for drinking and other uses. We can also help protect the water supply by not littering and picking up trash when we see it on the ground. We can also tell people, who we see doing something that will harm the water, to stop.

  9. Water Distribution

  10. The Water Cycle Rivers and Coast Water Cycle

  11. Credits Human Use of Freshwater Rivers and Streams Sources of Pollution Streamflow Water Cycle Image - Forest River Image - River Image - River Fishing Image - Water Runoff Image - Water Table Water Cycle Animation