key definitions Flashcards
afforestation
the planting of trees on land that has never had forest, or has been without forest for a long time
agricultural drought
a rainfall deficiency from meteorological drought that leads to deficiency of soil moisture and soil water availability, which has a knock on effect on plant growth and reduces biomass
aquifer
a permeable or porous rock which stores water
base flow
the normal, day to day discharge of the river
blue water
water stored in rivers, streams and lakes and groundwater in liquid form (the visible part of the hydrological cycle)
catchment
the area of land drained by a river and its tributaries
closed system
a sequence of linked processes with a transfer of energy but not matter between the parts of the system (the inputs and outputs happen within the system). An example is the global hydrological cycle
condensation
the change from a gas to a liquid, such as when water vapour changes into water droplets
convectional rainfall
often associated with intense thunderstorms, which occur widely in areas with ground heating such as the tropics and continental interiors
cryosphere
areas of the earth where water is frozen into snow or ice
cyclonic rainfall
a period of sustained, moderately intensive rainfall; it is associated with the passage of depressions
deforestation
the cutting down and removal of all or most trees in a forested area
desalination
the process of converting saltwater to freshwater suitable for human consumption and industry
desertification
land degradation in arid, semi-arid and dry sub-humid regions resulting from various factors, including climatic variations and human activities
dew point
the temperature at which dew forms; it is a measure of atmospheric moisture
drought
the definition varies internationally. According to the UN, drought is an extended period (a season, a year or several years) of deficient rainfall relative to the statistical average for a region measured over a very long period of time
economic water scarcity
occurs when water resources are available but there is insufficient human, institutional and financial capital to access the water in order to meet demand
ENSO cycle
a naturally occurring phenomenon that involves the movement of a mass of very warm water in the equatorial Pacific due to changes in the surface trade winds , atmospheric circulation and ocean currents
There are two phases- El Nino (warm water to the east) and La Nina (warm water to the extreme west)
eutrophication
excessive richness of nutrients in a lake or other body of water, frequently due to run-off from farming land, which causes a dense growth of plant life and death of animal life from a lack of oxygen
evaporation
the change in state of water from a liquid to a gas
evapotranspiration
the combined effect of evaporation and transpiration
falling or recessional limb
the part of a storm hydrograph in which the discharge starts to decrease and return to base flow
famine drought
a humanitarian crisis in which the widespread failure of agricultural systems leads to food shortages and famines with severe social, economic and environmental impacts
flash flooding
a flood with an exceptionally shot lag time- often minutes or hours
fossil water
ancient, deep groundwater from former pluvial (wetter) periods
frontal rainfall
occurs frequently in mid-latitudes when a warm tropical air mass meets a cooler polar air mass. The warmer air is less dense and rises over the colder air, which causes the warm air to cool , leading to condensation of water vapor, clouds of different types and precipitation
green water
water stored in the soil and vegetation (the invisible part of the hydrological cycle)
groundwater flooding
flooding that occurs after the ground has become saturated from prolonged heavy rainfall