CHAPTER A World of Rivers Rivers streams and creeks flow on every continent on Earth Water rushes over rocks and down a waterfall Beavers build dams with tree branches A bird swoops down and grabs a fish with its bill Crayfish munch on algae All sorts of creatures live in or near rivers People depend on rivers for survival too In the United States 65 percent of drinking water comes from rivers and streams Rivers are an important part of Earth's landscape
As much as humans rely on rivers they have caused much harm to this resource Human actions have endangered rivers Several rivers are running dry Others are severely polluted Some fish species that once thrived are now nearly extinct Experts believe that the world will suffer a major water crisis if rivers are not cleaned up and protected endanger to put at risk pollute to make something dirty or unsafe species a group of plants or animals that share common characteristics extinct no longer living an extinct species is one that has died out with no more of its kind Rivers around the world are becoming littered with trash
Parts of a River source the place where a river begins usually a spring glacier or lake tributary a creek stream brook or other river that flows into a larger river channel the course a river takes through land meander a bend or turn in a river's channel bank the land alongside a river floodplain area of land next to a river where water can overflow delta area of land that forms at the mouth of a river What is a River mouth where a river ends usually into another river or the sea A river is a body of freshwater Its current flows in one direction Rivers usually start in high places They flow downhill and empty into another body of water No two rivers are alike The shape and course of a river changes over time Some rivers such as the Rhine in Europe are deep and wide and flow slowly Other rivers such as the Trinity River in California rush quickly creating rapids and waterfalls Some rivers flow only during seasons of heavy rain Occasionally some rivers flow partly underground
current the movement of water in a river or an ocean ecosystem a group of animals and plants that interact with their surroundings invertebrate an animal without a backbone food web many food chains connected to one another Life in a River Rivers and the organisms they support form a complex ecosystem A perfect place for life to thrive rivers are home to almost every kind of organism Trees and other plants grow in the river and along its banks Insects and other invertebrates float on the surface and crawl on the riverbed below Rivers are filled with fish Frogs turtles snakes and otters also call rivers home Life too small to see such as phytoplankton is an important part of river food webs Fish are just one of many organisms in a river's ecosystem
