Drainage Basins Flashcards
What is a river’s drainage basin?
Area surrounding river where rainfall on land flows into that river
What is the boundary of a drainage basin?
Watershed
What type of system are drainage basins?
Open - matter + energy is input + output
What are the inputs and outputs of a drainage basin?
Input = precipitation Output = evapotranspiration, river discharge
What are the 6 stores of the drainage basin?
- Interception
- Vegetation storage
- Surface storage
- Soil storage
- Groundwater storage
- Channel storage
What is interception?
When precipitation falls on structures e.g. leaves or buildings before reaching soil
Where does interception act as a large water storage?
Wooded areas
Why is interception storage temporary?
Collected water evaporates or flows as througfall
What is vegetation storage?
Water absorbed by plants - includes all water within a plant
What is surface storage?
Includes puddles, ponds and lakes
What is soil storage?
Moisture in soil
What is groundwater storage?
Water stored in ground - as soil moisture or in rocks
What is the water table?
Top surface of the zone of saturation - area where all pores in rock and soil are saturated
What are aquifers?
Porous rocks that hold water
What are 2 stores are part of groundwater storage?
Water table
Aquifers
What is channel storage?
Water held in river
What are the 10 flows in a drainage basin?
- Inflitration
- Overland flow
- Throughfall
- Stemflow
- Throughflow
- Percolation
- Groundwater flow
- Baseflow
- Interflow
- Channel flow
What is infiltration?
What is infiltration rate affected by?
Water soaking into soil
- Soil type
- Soil water content
- Soil structure
What is overland flow? Why does it happen?
Water flowing over land
Occurs bc rainfall onto ground is faster than infiltration rate
What is throughfall?
Water dripping from one leaf to another
What is stemflow?
Water running down a plant stem
What is throughflow?
Water slowly moving downhill through soil.
What is percolation?
Water seeping down into water table
What is groundwater flow?
Water flowing below water table through permeable rock
What is baseflow?
Groundwater flow that feeds into rivers through river banks + beds
What is interflow?
Water flowing downhill through permeable rock above water table
What is channel flow?
Water flowing into river itself. Also known as river discharge.
What are the 4 outputs of the drainage basin?
- Transpiration
- Evaporation
- Evapotranspiration
- River discharge
What is transpiration?
Evaporation from within leaves
What is evaporation?
Water turning into water vapour
What is evapotranspiration?
Combo of transpiration and evaporation
What does the Water Balance show?
Balance between inputs and outputs of drainage system
What are the 3 reasons for why the Water Balance varies seasonally in the UK?
- Precipitation exceeds evapotranspiration in wet season - creates water surplus - ground stores fill with water - more surface runoff + higher discharge - river levels rise
- Precipitation lower than evapotranspiration in dry season - ground stores depleted - some water absorbed by plants + some water flows into river, but isn’t replaced by precipitation
- End of dry season = water deficit. Ground stores are depleted next wet season.
