The volume of water that flows in a river per second
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What is discharge measured in?
Cumecs, cubic meters per second (m3/s)
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What is peak discharge?
The highest point on the hydrograph
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What is lag time?
The length of time between peak rainfall and peak discharge
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What is the rising limb?
Water flowing into the river as discharge increases
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What is the falling limb?
The decrease in river discharge as the volume of water returns to its normal level
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Name 8 things that affect river discharge
Precipitation, Rock type, Urbanisation, Temperature, Vegetation, Size, Soil and Slope
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How can temperature increase discharge?
If it is cold there will be less evaporation and transpiration to remove water before it reaches the river. Snowmelt can also add a sudden influx of water
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How can urbanisation effect discharge?
If an area is less built up, there are fewer impermiable surfaces so there is more infiltration and percolation which increases lag time and there is less drainage leading straight to the river
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How does vegetation decrease discharge?
They take up water through their roots and act as a natural barrier which increases lag time
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How can soil type increase discharge?
If the soil has already been saturated/frozen/parched then it can't absorb as much water and its infiltration capacity will be reduced so surface run off will increase
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How can rock type decrease river discharge?
Permiable rock types such as chalk and limestone let more water percolate and travel via ground-water flow
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How do slopes affect discharge?
Steeper slopes have greater overland flow whereas a lower gradient slope will have more infiltration and through-flow
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How can size affect river discharge?
The bigger the drainage basin, the higher the discharge is because there is more area fo the rain to fall on
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How can the type of precipitaion reduce discharge?
Slow, light rain is absorbed by infiltration into the soil so the river has longer to respond. It also helps if the precipitation has not happened too much before
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