The Hydrological Cycle

Drainage basins are local open systems.

A river's drainage basin is the area surrounding the river where the rain falling on the land flows into that river - also known as the river's catchment.

The boundary of a drainage basin is the watershed so any precipitation falling beyond the watershed enters a different drainage basin.

Inputs are water coming into the system, for example precipitation - rain, snow, hail, dew and frost - including all the ways moisture comes out of the atmosphere.

There are five ways water is stormed in the system.

One. Interception - precipitation lands of vegetation/buildings/concrete/tarmac before it reaches the soil. This creates a significant store of water in wooded areas but this is only temporary as it evaporates quickly.

Two. Vegetation storage - water that has been taken up by plants and is all the water contained in plants at any one time.

Three. Surface storage - water in puddles (depression storage), ponds and lakes.

Four. Ground water storage - water stored in the ground by soil (soil moisture), or in rocks. This water table is the top surface of the zone of saturation. The zone of saturation is the zone of soil or rock where all the pores in the soil or rock are full of water. Porous rocks that hold water are called aquifers.

Five. Channel storage - the water held in a river of stream channel.

There are lots of different ways water moves from one place to another. These are flows and processes:

One. Surface run off (or overland flow) - water flowing over the land. It can flow over the whole surface or in little channels, and is common in arid areas where torrential rains on hard baked land.

Two. Throughfall - water dripping from one…