Drainage basin key terms

• Precipitation (Input)


  Rain, hail, sleet or snow.

  Duration and intensity will impact processes within the system.
• Condensation (input)


  Water vapour turning to liquid.

  May form fog.
• Vegetation (store)


  Plants are 80 to 90% water; take in water from soil moisture store through their roots.

  Vegetation cover intercepts the precipitation and a store may be held on leaves and branches.

  Tropical rainforests can intercept 58% of rainfall.
• Surface storage (store)


  Occurs in built environments as puddles.

  Occur in natural environments as puddles when the soil moisture store is waterlogged, when the water intensity is higher than infiltration rate, or when on impermeable rock.
• Soil moisture (store)


  Pore spaces between soil particles fill with water and air. The amount of pore space varies in different soils: clay has 40 to 60% volume, whereas sand has 20 to 45%.
• Groundwater (store)


  Water stored underground in permeable and porous rocks.
• Channel (store)


  The volume of water in a river channel.
• Stemflow (transfers)


  Water flows down the stems of plants and trees.
• Infiltration (transfer)

  Water on the surface soaks into the soil.

  The speed with which this happens is the infiltration rate.

  Texture, structure and organic content of soil all affect infiltration rate.

  The rate normally declines during the early part of a storm.
• Overland flow (transfer)


  Rainfall flowing over the ground surface either because the soil is saturated or because the rainfall is exceeding the soil infiltration capacity.
• Channel flow (transfer)


  The flow of water in rivers.
• Throughfall (store)


  Water moving from vegetation to the ground.
• Throughflow (stores)


  The lateral movement of water down a slope to a river channel. Slower than overland flow but the rate is increased by root systems of vegetation.
• Percolation (transfer)


  Downward movement of water into underground stores.
• Groundwater flow (transfer)


  Downward and lateral movement of water within saturated rock. This is a very slow movement.

  Water-bearing rocks are called aquifers.
• Evapotranspiration (output)


  Combined loss of water at the surface through evaporation and transpiration by plants.
• Leakage (output)


  Loss from groundwater stores.
• Run-off (output)


  The movement of water across the land surface.