Factors affecting water flows and stores

Factors affecting water flows and stores

1. Water flows

   • SURFACE RUN OFF: water which flows QUICKLY across the surface
     • Human factors affecting surface run off
       • Deforestation
         • Cutting down trees means there are no leaves to INTERCEPT rainfall. Rain reaches the ground very quickly and the soil can become saturated. The water cannot INFILTRATE the soil so surface run off rates INCREASE.
           • High levels of surface run off mean water is finding its way to the river very quickly. This means the river is much more likely to flood.
       • Urbanisation
         • Urban areas are covered in concrete and tarmac. This stops rainfall INFILTRATING into the underlying soil. This INCREASES surface run off rates.
           • High levels of surface run off mean water is finding its way to the river very quickly. This means the river is much more likely to flood.
       • Farming
         • Ploughing fields removes vegetation preventing INTERCEPTION. Ploughing the land can create channels which funnel water downhill. Both of these things increase surface run off rates
           • High levels of surface run off mean water is finding its way to the river very quickly. This means the river is much more likely to flood.
     • Physical (natural) factors affecting surface run off
       • Geology
         • NON POROUS rock does not have any gaps in it. This means it cannot store water. When it rains, the soil above it becomes saturated very quickly because the water cannot PERCOLATE into the underlying rock. This increases surface run off rates.
           • High levels of surface run off mean water is finding its way to the river very quickly. This means the river is much more likely to flood.
       • Prolonged or heavy rainfall can prevent rainwater infiltrating into the soil (either because it is saturated or because the rain is falling faster then it can infiltrate). This increases surface run off rates.
         • High levels of surface run off mean water is finding its way to the river very quickly. This means the river is much more likely to flood.
   • THROUGH FLOW: water which flows SLOWLY through the soil
   • GROUNDWATER FLOW: water which flows very SLOWLY through the underlying rock

2. Water stores

   • surface water e.g. rivers, lakes and reservoirs
     • Weather. During periods of prolonged or heavy rainfall, stores of water in the drainage basin will increase.
   • soil
     • Weather. During periods of prolonged or heavy rainfall, stores of water in the drainage basin will increase.
   • rocks
     • Geology
       • Porous rocks have gaps (pores) where water can be stored. Limestone is a porous rock.
       • Non porous rocks have no spaces so they cannot store water
     • Weather. During periods of prolonged or heavy rainfall, stores of water in the drainage basin will increase.