drainage basin system

• Precipitation


  water falling from the atmosphere, in any 3 states
• channel precipitation


  Precipitation that falls directly into the river channel
• Interception


  Water being prevented from reaching the surface by trees or grass
• Stemflow


  the flow of intercepted water down the trunk or stem of a plant
• Through fall


  Water dripping from one leaf to another
• Infiltration


  movement of water downwards from the surface into the soil
• infiltration capacity


  the maximum rate at which soil can absorb water
• Percolation


  movement of water down through the pores in the soil into the groundwater zone
• Throughflow


  water flowing through the pores in the soil, parallel to the surface, to the river channel
• Porosity


  proportion of pore space to solid material
• Permeability


  ease with which water will pass through a substance
• Hortonian overland flow


  water runs over the surface because the intensity of the precipitation is higher than the infiltration capacity of the surface
• Saturated overland flow


  water runs over the surface because the ground below has become saturated and no further infiltration can occur
• water table


  upper layer of permanently saturated pore spaces in the ground water zone
• saturated zone

  area of subsurface where all pore space is filled with water
• Base flow


  the slowest form of water movement through rock, and accounts for the constant flow of water in rivers during periods of low rainfall
• Recharge


  new water from precipitation that refills the baseflow levels after abstraction
• Hydrostatic pressure


  force exerted by water in the groundwater zone
• Aquifer


  a sufficiently permeable water-bearing rock that is above a layer of rock that prevents the water from seeping away
• Aquitard


  an area of low permeability
• Aquiclude


  an area of zero permeability
• Spring


  water seeps directly out of the ground where an aquifer reaches the surface