Rivers and streams provide humans with necessities like drinking water and crop irrigation; they also provide areas to recreate, relax and have fun. Riparian areas provide essential habitat for fish and wildlife as well.
Earth's Hydrologic Cycle
Rivers and streams are the land component of the global water cycle. There is no beginning or end to this cycle; all water exists in some part of this cycle at all times. Oceans store water, and it evaporates into clouds. It precipitates and returns to the land as rain, snow or ice. Rain and melting snow and ice feed creeks and streams that flow into rivers. Rivers carry the water back to the ocean and the cycle continues.
Natural and Human Caused Impacts
Riparian habitats respond to climactic changes and human activities. Seasonal and annual cycles of erosion and deposition, flooding and changes in temperature and rainfall are natural fluctuations. Humans impacts include diversion of rivers and streams for irrigation, drinking water, flood control levees, canals for ship navigation and dams to produce electricity.
Human Uses Impact Wildlife and Habitat
Salmon are anadromous fish that hatch in creeks and streams. As juveniles, these fish move downstream and enter the ocean, where they grow into adults. Adults return to creeks and streams to lay their eggs. Dams disallow them access to their native streams to spawn. Human diversions of rivers and streams also disrupt food webs. When tiny fish get caught in irrigation equipment, bigger fish go hungry. Meeting the needs of humans as well as wildlife is an ongoing challenge.