Evaporation: The process by which liquid water is transformed into water vapour (gas). A large amount of energy is required for this to occur. The energy is usually provided by heat from the sun.
Evapotranspiration: Total amount of moisture removed by evaporation and transpiration from a vegetated land surface. Transpiration is the process by which water is lost through the stomata in a plant's leaves.
Groundwater Flow: Slowest transfer of water in the drainage basin. Provides the main input of water into a river during drought or dry seasons. Groundwater flows at a slow but steady rate through bands of sedimentary rock. It can take thousands of years for moisture under permeable rocks to return to the drainage basin.
Infiltration: Passage of water into the soil. Takes place relatively quickly at the beginning of a storm but as the soil becomes saturated the infiltration rate falls rapidly.
Interception: Process by which raindrops are prevented from directly reaching the soil surface. Leaves and branches intercept water.
Perlocation: Downward movement of water within the rock under the soil surface. Rate of perlocation depends on the nature of the rock.
Precipitation: Water in any form that falls from the atmosphere to the surface of the Earth. It includes rain, snow, sleet and hail.
Runoff: All the water that enters a river eventually flows out of the drainage basin. It can be quantified by measuring a river's discharge.
Stemflow: Water that runs down the stems and branches of plants and trees during and after rain. Takes place after interception.
Throughfall: Water that drips off leaves during a rainstorm. It occurs when more water falls onto the interception layer of the tree canopy..
Throughflow: Water that moves down-slope through the subsoil, pulled by gravity.
Deposition: Laying down of solid material, sediment, on the bed of a river or sea floor.
Erosion: Break up of rocks by the action rock particles being moved over the Earth's surface by water, wind and ice.
Transporation: Movement of particles from the place they were eroded to the place where they're deposited.
Incised Meander: Caused by rejuvenation. A meander that has cut deeply into the floodplain creating steep banks.
Knick Point: Marked by rapids, represents rejuvenation and is a sudden break in the long profile of the river.
Rejuvenation: Increase in the energy of a river caused by either a fall in its base level or an uplift of land.
River Terrace: Narrow, flat peice of ground that runs parallel to the river on either side, above the level of the floodpain. (Usually created from a fall in base level).
Hazard: Natural event that threatens life and property. Disaster is the realisation of the hazard.
River Management: River basins are subject to strategies designed to prevent flooding and to ensure that there is an adequate supply of water.