Drainage Basins(water cycle) Flashcards
What is a drainage basin?
1) A river’s drainage basin is the area surrounding the river where the rain falling on the land flows into that river. The area is also called the river’s catchment.
2) The boundary of a drainage basin is the watershed- any precipitation beyond the watershed enters a different drainage basin.
3) Drainage basins are open systems with inputs and outputs.
4) Water comes in as precipitation and leaves via evaporation, transpiration, and river discharge.
Name the Inputs- water coming into the system.
Precipitation includes all the way moisture comes out of the atmosphere.
Precipitation is mainly rain, but it also includes other types like snow, hail dew, and frost.
Name the Outputs - water leaving the system
-Evaporation is water turning into water vapour.
-Transpiration is evaporation from within leaves- plants and trees take up water through their roots and transport it to their leaves where it then evaporates.
-Evapotranspiration is the process of transpiration and evaporation together.
- River discharge, or river flow, is another output.
Name storages- water stored in the system
> Interception- when precipitation lands on vegetation or other structures, like buildings, concrete or tarmac surfaces before it reaches the soil.
Interception storage is only temporary because the collected water may evaporate quickly, or fall through leaves as through fall.
> Vegetation storage- water thats been taken up by the plants. Its al the water contained in plants at any one time.
> Surface storage- includes water in puddles, ponds and lakes.
> Soil storage- includes moisture in the soil.
> Groundwater storage- water stored in the ground, either in the soil or in rocks.
> Channel storage- Water held in the river or stream channel.
Name the flows- water moving from one place to another.
> Surface runoff- water flowing over the land. It can flow over the whole surface or in little channels. This occurs when rain is falling on the ground faster than infiltration.
> Through fall- water falling from one leaf to another.
> Stem flow- water running down a plant stem or tree trunk.
> Through flow- water moving slowly downhill through the soil.
> Percolation- water seeping down through soil into the water table.
> Groundwater flow- water flowing slowly below the water table through permeable rock.
> Base flow- groundwater flows that feeds into rivers through river banks and river beds.
> Interflow- water flowing downhill through permeable rock above the water table.
> Channel flow- water flowing in the river or stream itself. This is also called the rivers discharge.
Concept of the water balance
The water balance looks at how the amount of precipitation compares with the water leaving the system as runoff or as evapotranspiration.
- In wet seasons, precipitation exceeds evapotranspiration. This creates a water surplus.
-In drier seasons, precipitation is lower than evapotranspiration.
