Geography physical drainage basin
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What is the mouth of the river?
Where the river flows into the sea or sometimes into a lake
What is the watershed?
The boundary dividing one drainage basin from another - a ridge of higher land
what is a confluence?
The point at which two rivers join
what is the source of he river
The upland area where the river begins
what is the catchment?
The area from which water drains into a particular drainage basin
what is a tributary
A river which joins a larger river
what is a drainage basin?
The area which is drained by a river and its tributaries
what is drainage density?
The total length of all the streams in the basin divided by the total area of the basin
what is transpiration
Water vapour released through the stomata in leaves
what is through-flow
The flow of water beneath the ground’s surface
what is condensation?
When water vapour turns into liquid water as it cools
what is evapouration?
Water droplets are turned into water vapour
What is surface runoff?
The flow of water over the surface of the ground
what is precipitation?
Water that falls through the air e.g. snow, rain, hail
what is drip fall?
Droplets that fall from the leaves of trees to the ground
what is infiltration?
Water passing from ground level through to the soil
what is an interception?
Objects that prevent water from reaching the ground
what is percolation?
Water seeping through the soil layer to the rock layer
what is the water table?
The level below which the ground is saturated with water.
what is groundwater flow?
Water that travels underneath and parallel to the surface
what is soil moisture storage?
water held in the soil layer
What is insolation?
what is the river channel storage?
Water held within the banks of the river
what is stem flow?
Water which runs down the stems and branches in the ground layer. Takes place after interception has occurred
what is base flow?
Product of groundwater seeping slowly into the bed of the river
what is surface storage?
- Water held on top of the ground, for example puddles
- this may be due to the fact that the ground surface is impermeable
what is an aquifer?
Permeable rock which contains groundwater
what are storm hydrographs?
Graphs on which river discharge during a storm, or single precipitation event, is plotted against time
what is river discharge?
volume of water passing through a cross-section of a river during a given time period. Measured in cumecs
What is the 'lag time' on a storm hydograph?
Period of time between the end of rainfall and the peak discharge
How does precipitation reach ground before it is transported?
- 1. Direct channel input (water falls straight into channel)
- 2. Interception followed by stemflow or drip-fall
- 3. Infiltration
- 4. Percolation
How is water transported to the river channel?
- 1. Overland flow2. Throughflow3. Base flow
List throughflow, baseflow and overland flow in order of speed from fastest to slowest
- Overland flow
- Through flow
- Base flow
What is antecedent discharge?
Level of discharge before the storm which is lower in the summer and higher in the winter
Which process is the most common way for discharge to reach the channel?
Which process is the least common way for discharge to reach the channel?
Base flow, which responds slowly to precipitation inputs
What is the case study for how different factors effect river discharge?
The River Ribble, Lancashire UK
Describe and explain a case study for how different factors effect river discharge
- The River Ribble in Lancashire, UK
- 110km long
- joins the irish sea at Preston
- During intense storms there is a short lag time and a high peak in discharge
- the rock type is impermeable Millstone Grit and limestone resulting in lots of overland flow
- the soil type is peat soil, which is a major store of groundwater
- the basin shape is elongated and the largest in NW england.
- maximum rainfall is 1775mm
- heavily urbanised surrounding forces more water into the Ribble through surface run-off
- agriculture along the Ribble has lead to degration of vegetation cover (animals eat the grass) and means higher amounts of water enter river
What factors effect the shape of a hydrograph? List 10
- Insolation levels
- geology of rock
- vegetation cover
- thickness of soil
- size of river
- level of the water table
- height of existing water
- size of drainage basin
How does the size of the drainage basin effect the shape of the hydrograph?
Lag time is shorter and peak is higher in a small basin compared to a big basin
How does the shape of the drainage basin effect the shape of the hydrograph?
Lag time is shorter and peak is higher in a more circular basin compared to an elongated one
How does the relief of the land effect the shape of the hydrograph?
Lag time is shorter and peak is higher in a steeper basin
How does the length of precipitation event effect the shape of the hydrograph?
Lag time is shorter and peak is higher after prolonged precipitation
How does the intensity of precipitation effect the shape of the hydrograph?
Lag time is shorter and peak is higher after intense rainfall
How does the type of precipitation effect the shape of the hydrograph?
Lag time is slower and peak is slower after snowfall because snow is stored on the ground surface
How does the permeability of the rock effect the shape of the hydrograph?
Lag time is shorter and peak is higher in an area of impermeable rock type because they are saturated more quickly than porous rock
How does the level of vegetation effect the shape of the hydrograph?
Lag time is slower and peak is lower in a forested basin because vegetation intercepts a large proportion of precipitation
How does the soil texture and structure effect the shape of the hydrograph?
Lag time is slower and peak is lower in areas od sandy soil because they have larger pores than clay soil
How does urbanisation effect the shape of the hydrograph?
Lag time is faster and peak is higher in a urbanised catchment because surface run-off is higher
How does deforestation effect the shape of the hydrograph?
Lag time is faster and peak is higher because there is nothing to intercept precipitation or allow for evapotranspiration
What is the river regime?
the changing pattern of river discharge over a period of time, usually a year
How can summer effect the river regime?
- higher levels of interception and evapotranspiration
- increased rate of human abstraction, due to increased demand
How does winter effect the river regime?
- Less interception and evapotranspiration
- Snow and ice will increase river discharge
A substance that allows water to pass through it
A substance that doesn't allow water to pass through it
a material which has tiny pores that allow water to pass through it e.g. clay
a material which doesn't allow liquid or air to pass through it e.g. granite
a substance that has cracks, joints or bedding planes that allow water through e.g. limestone
Why does precipitation usually exceed evapotranspiration rates, resulting in a positive water budget/balance?
The climate is temperate
What is a soil moisture surplus?
When precipitation levels are higher than evapotranspiration levels. Happens in winter
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