Factors Affecting River Discharge

Factors Affecting River Discharge

1. Basin Shape and Size

   • A larger basin with more tributaries and upland areas bordering it will force more water down to the river and so increase discharge
   • A flatter, smaller area of ground with fewer waterways will reduce the amount of water reaching the river and so discharge will be less

2. Type of Precipitation

   • Solid precipitation, eg snow, will settle and hold water for periods of time, this reduces river discharge
   • Liquid precipitation, eg rain, will flow much faster toward the channel so increase discharge
   • More gaseous forms, eg fog/mist, will again take longer to reach the channel so reduce discharge

3. Land Use

   • If land has been farmed it will be more compact so speed up surface run off and increase river discharge
   • If land has been left untouched however water will more easily infiltrate the soil so discharge will decrease

4. Geology

   • Permeable rock will allow water to infiltrate it and so lengthen the time before it reaches the channel, therefore reducing river discharge
   • Impermeable rock however will not allow water to percolate into it, forcing it to remain in the soil and reach the river faster, thus increasing discharge

5. Relief

   • Steep ground will force water to flow faster and reach the channel faster, therefore increasing discharge
   • Land with a lower gradient will make water flow slower and so reduce discharge

6. Soil

   • Small particles making up the soil, such as clay, will force more surface run off and so increase river discharge
   • Larger particles in the soil, such as sand, allow water to more easily infiltrate it and become stored. This slows the time it will take to reach the river channel and so reduce discharge

7. Urbanisation

   • Land covered in impermeable and man-made surfaces will force water into drains and the river channel much faster and so discharge will rapidly increase
   • Soil allows for water to infiltrate and become stored, this reduces river discharge

8. Deforestation

   • Land where trees have been removed will experience reduced interception and transpiration levels and so discharge will increase.
   • Trees covering the land however will intercept water before it becomes surface run off and so increase the time it takes for it to reach the river channel and so reduce discharge

9. Amount of precipitation

   • Heavy liquid precipitation will saturate the ground quickly and force more water into the river channel, thus increasing discharge
   • Light, or solid, precipitation will become stored easier and so take longer to reach the channel and so discharge will drop