Hydrologic cycle

   Hydrology deals with rainfall and run off.

    water from water bodies such as oceans and lakes evaporates due to the heat energy of solar radiation and its precipitation on earth is known as hydrologic cycle.

      Due to the Evaporation water moves upward and forms cloud. While much of the cloud condense and fall to the ocean as rain, a part of cloud is drain to the land areas by winds.
     Then they condense and precipitate into land mass as rain,  snow, hail, sleet etc.
Another part may be interapted by vegetation, structures and other such modifications from which it may be either evaporated back to the atmosphere or move down to the ground water body.

       Vagetation send a portion of water from under the ground surface look to the atmosphere through the process of transpiration.
      Precipitation reaching the ground surface after meeting the needs of infiltration and Evaporation moves down the slope over the surface.

      The ground water may come to the surface through spring and other outlet of the spending a considerable longer time then the surface flow.
   The portion of precipitation which buy a veriety of paths above and below the screen channel is called runoff.
     Once it enters the screen channel, run off becomes screen flow.