Drainage Basin Terms And Definitions Flashcards
Evaporation
The transformation of water droplets into water vapour in the atmosphere by heating.
Precipitation
All forms of moisture that is transferred from the atmosphere to the earth’s surface, subsequent to evaporation and condensation e.g. Rain, hail, sleet or snow.
Potential evaporation
The amount of water loss that would take place from a surface given unlimited supply of water.
Transpiration
Transformation of moisture from within a plant’s leaves to become water vapour in the air, via the minute pores i.e. stomata.
Evapotranspiration
Collective name for evaporation and transpiration.
Condensation
The process which water vapour is converted to water droplets (usually visible as cloud). It usually accompanies a fall in temperature and requires condensation nuclei.
Sublimation
Transfer of water from its solid form (ice) directly into its gas form (water vapour).
Interception
The interruption of precipitation falling to the earth’s surface. Water or snow can be stored temporarily on leaves of plants, trees, buildings etc.
Leaf drip/throughfall
Intercepted water falling from leaves to the ground surface.
Stem flow
Intercepted water trickling down stems and branches to the ground.
Surface storage
Water which lies on the surface of the ground e.g. lakes, ponds, puddles, and reservoirs.
Surface runoff/overland flow
The movement of water over the surface of the land, usually when the ground is saturated or frozen or when precipitation is too intense for all to infiltrate.
Channel flow
The movement of water within the river channel.
Infiltration
The downward movement of water into the ground surface. N.b. water seeps vertically into the soil/rock through pores (air spaces).
Infiltration capacity/rate
The maximum rate at which water can pass through the soil (mm/hr).
Field capacity
When soil is saturated i.e. all available pore spaces between soil particles are filled.
Throughflow
The movement of water laterally/downslope through the soil ( above water table).
Percolation
The downward movement of water in the soil or rock layers, due to gravity.
Groundwater storage
Water stored beneath ground surface in permeable ground strata (usually above an impermeable rock layer) creating a zone of saturation.
Water table
The upper level of the zone of saturation.
Groundwater flow
The lateral movement of water below the water table or in underlying rock strata.
Stream/channel flow
Water moving over the surface in a contained channel.
Recharge
When groundwater stores depleted by a dry spell are refilled by water percolating through soil and rock layer.
Channel catch
Precipitation falling directly into a stream or river - a small % of precipitation as most falls into the drainage basin.
