Other terms used interchangeably are watershed, drainage basin, water basin and drainage area.
They are important in hydrology (study of water).In the hydrological cycle, movement of water is studied by focusing on catchment. Rain gauge data is used to measure the precipitation or rain over an area. Stream gauge located at the outlet of the catchment is used to measure the water discharge from the catchment.
It is important in ecology. Flowing water picks up sediments, nutrients and pollutants. Minerals and artificial fertilizers are added by man and these are deposited near the mouth of the catchment. Hence, the natural mineral balance is disturbed.
River Itchen: The land drained by the river consists of a gravelly loam in the upper chalk. There are many water channels that drain the grasslands near the river. At Itchen Abbas the water level is higher than the surrounding marshes. The numerous channels make is very difficult to carry out any survey here.
Shape: Water from a circular catchment reaches the river faster than the long, thin catchment. The landscape of the area was shaped by stream erosion when the ground was frozen, causing rainfall to run over the surface rather than soaking into the chalk.
Rainfall on the sandy soil is absorbed by the ground and only a part of it reaches the river. ...