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Kelly Coulter Rivers often begin in the mountains. You can follow one small stream and see it connects with another, they will then flow into a small river. Eventually this path leads to a large river. Colorado River The streams and smaller rivers that feed into a main river are called TRIBUTARIES. A river and all its tributaries together make up a river system. The land area that supplies water to a river system is called watershed. (aka: drainage basins) So large rivers may be tributaries of still larger rivers. When rivers join another river system, the areas they drain become part of the largest river’s watershed. You can identify a river’s watershed on a map by drawing an imaginary line around the region drained by all its tributaries. What keeps watersheds separate? One is separated from another by a ridge of land called a DIVIDE. Streams on each side flow in different directions. Continental Divide (longest in U.S.A.) follows the line of the Rocky Mountains The Continental Divide, also called the Great Divide, is a natural boundary line separating waters that flow into the Atlantic Ocean or Gulf of Mexico from those that flow into the Pacific Ocean. It runs north-south from Alaska to northwestern South America. In the conterminous United States, it follows the crest of the Rocky Mountains. http://nationalatlas.gov/mld/condivl.html Ponds are smaller and shallower than lakes. Sunlight usually reaches to the bottom of all parts of a pond. How ponds form: ◦ Form when water collects in hollows and low-lying areas of land. Exploring ponds: ◦ Muddy bottom often covered in weeds. This is because sunlight is able to reach the bottom of these shallow waters. ◦ A quiet pond is a thriving habitat for many living things. ◦ Not all ponds exist year round. Some only in spring, dry up in the summer due to evaporation. Lakes are generally deeper and bigger than ponds. In addition, sunlight does not reach the bottom in a deep lake, as it does in a pond. No plants and few other organisms can live in a lake’s chilly depths. Some may form the same as lakes Great Lakes, formed in depressions created by ice sheets that melted at the end of the Ice Age. Other lakes were created by movements of Earth’s crust, Lake Victoria and Lake Tanganyika Others are the result of volcanoes, an eruption can cause a flow of lava or mud that blocks a river and forms a lake. Some form in empty craters. People create lakes by building a dam (Lake Mead) Is a land area that is covered with water during part or all of the year. Help control floods Provide habitats for many species. Three types of fresh water wetlands are MARSHES, SWAMPS, and BOGS ◦ marshes- grassy areas covered by shallow water or a stream. ◦ swamps- look more like flooded forests, located in warm, humid climates ◦ Bogs- more common in cooler northern areas. Often form in depressions left by melting ice sheets thousands of years ago. (water tends to be acidic) marsh swamps bogs Along coasts usually contain both fresh and salt water. Coastal wetlands include salt marshes and mangrove forests. ◦ Salt marshes-found along both U.S. coasts ◦ Mangrove- found along the southeastern coast of U.S. Salt marsh mangrove Water is the key to the Everglades, a vast marsh in south Florida. Home to many kinds of wildlife; alligators, fishes, snakes, wading bird, panther, manatee Humans threaten the area with farming chemicals. Water that once flowed has been diverted for farming and household use. New organisms brought in as pest control compete with the already existing organisms. Because of their sheltered waters and rich supply of nutrients, wetlands provide habitats for many living things. Wetlands act as natural water filters. They also help control floods by absorbing extra runoff from heavy rains. Wetlands are like giant sponges When destroyed, floodwaters are not absorbed, the water runs off the land quickly, worsening flood problems. Because of these important functions