Drainage Basins Flashcards
What are drainage basins?
Natural systems viewed as open local hydrological cycles
What is a rivers drainage basin?
The area surrounding the river where the rain falling on the land flows into the river?
What else can a rivers drainage basin be called?
Catchment area
What is the boundary of the drainage basin?
Watershed - Any precipitation falling beyond the watershed enters a different basin
What enters and leaves the system?
Water enters as precipitation and leaves via transpiration, evaporation and river discharge
What is an input of the system?
Precipitation
How is precipitation an input?
Includes all the ways moisture comes out of the atmosphere. It is mainly rain however can be snow, hail, dew and frost
What are the 6 types of stores?
- Interception
- Vegetation Storage
- Surface Storage
- Soil Storage
- Groundwater Storage
- Channel Storage
Explain Interception
When some precipitation lands on vegetation or other structures, like buildings, concrete or tarmac. It creates a significant store of water in wooded areas. Interception storage is only temporary because the collected water may evaporate quickly or fall from the leaves as through fall
Explain vegetation storage
Water that’s been taken up by plants. It’s all the water contained in plants at any 1 time
Explain surface storage
Includes water in puddles (depression storage), ponds and lakes
Explain soil storage
Includes moisture in the soil
Explain Groundwater storage
Water stored in the ground, in rocks or soil. The water table is top surface of the zone saturation. porous rocks that hold water are called aquifers
What is the zone of saturation
The zone of soil or rock where all the pores are full of water
What are porous rocks
Rocks with big holes in them
What is channel storage
Water held in a river or stream channel
What are the 10 types of flows?
Infiltration, Overland flow / runoff, Through fall, Stem flow, Through flow, Percolation, Groundwater flow, Base flow, Interflow and Channel flow / River discharge
Explain Infiltration
Water soaks into the soil. Infiltration rates are influenced by soil type, soil structure and how much water is already in the soil
Explain Overland flow / runoff
Water flowing over the land. It can flow over the whole surface or in little channels. It happens because rain is falling on the ground faster than infiltration can occur
Explain Through fall
Water dripping from 1 leaf to another
Explain Stemflow
Water running down a plant stem or tree trunk
Explain Throughflow
Water moving slowly downhill through the soil. Throughflow is faster through pipes - Things like cracks in the soil or animal burrows
Explain Percolation
The water seeping down through soil into the water table
Explain Groundwater Flow
The water flowing slowly below the water table through permeable rock. Water flows slowly through most rocks, but rocks that are highly permeable with lots of joints have faster groundwater flows
Explain Baseflow
Groundwater flow that feeds into rivers through riverbanks and river beds
Explain Interflow
Water flowing downhill through permeable rock above the water table
Explain Channel flow / River Discharge
Water flowing in the river or stream itself
What are the 4 outputs?
Evaporation, Transpiration, Evapotranspiration and River discharge or flow
Explain Evaporation
Water turning into water vapour
Explain transpiration
It’s evaporation within leaves - plants and trees take up water through their roots and transport it to their leaves where it evaporates into the atmosphere
Explain Evapotranspiration
The process of evaporation and transpiration together
What is Potential Evapotranspiration (PET)?
It’s the amount of water that could be lost by evapotranspiration. Actual evapotranspiration is what actually happens
Give an example of PET
A desert PET is high (because heat increases evaporation) but actual transpiration is low (because there isn’t much moisture)
Explain River Discharge or flow
The discharge of a river is the volume of water which flows through it in a given time. Normally measured in cubic metres per second
What does the Water Balance Show?
The balance between inputs and outputs.
How is the water balance worked out?
From the inputs (precipitation) and outputs (channel discharge and evapotranspiration). The water balance is how much water is stored in the system
How is the water balance shown in the UK?
Shows seasonal patterns
What happens in wet seasons?
Precipitation exceeds evapotranspiration creating a water surplus. The ground stores fill with water so there’s more surface runoff and higher discharge, So river levels rise
What happens in drier seasons
Precipitation is lower than evapotranspiration. Ground stores are depleted as some water is used by plants and humans and some flows into the river channel but isn’t replaced by precipitation
What happens at the end of the dry season
Theres a deficit of water in the ground. The ground stores are recharged in the next wet season
