Drainage Basin: area of land drained by a river and its tributaries

Watershed: boundary between two river systems on high relief land

Precipitation: deposition of moisture from the atmosphere to the surface. Can be: snow, rain, sleet, snow, hail, frost, fog...

Evapo-transpiration: release of water vapour from the earths surface in the form of evaporation and transpiration.

Interception: retaining of water by plant leaves, stems and branches. Water is stopped from reaching the soil directly.

Stem-flow/leaf drip: water that travels through the stem of a plant.

Surface run-off/overland flow: the flow of water over the surface of the ground.

Infiltration: water that soaks down into the soil.

Soil moisture storage: moisture held stationary in the soil.

Through-flow: the movement diagonally downward of water through the soil.

Percolation: the filtering of water donwards vertically through the joints and pores of permeable rock.

Through-fall: droplets of rain dripping straight off leaves and onto the ground.

Groundwater flow: water that flows horizontally underground through rock.

Soil saturation: when the soil contains a lot of water.

Field capacity: the volume of water which is the maximum the soil can hold.

Infiltration rate: the rate at which water infiltrates into the soil.

Water-table: the level below which the ground is saturated.

The water balance:

precipitation = runoff + evapotranspiration +/- change in storage

Dynamic Equilibrium: refers to balanced state of a system when opposing forces are equal. If one element in the system changes then the system changes to reach equilibrium again.