Use the back button on the browser to return to your page	Glossary
	for the Great Stour case study

	Abstraction	The removal of water before it enters the river.
	Aquifer	A layer of permeable rock sandwiched between two layers of impermeable rock. E.g. a layer of chalk sandwiched between two layers of clay. The chalk layer becomes saturated with water - this is called an aquifer.
	Base flow	The water flowing in a stream which is fed by ground water. During dry periods it is only the base flow which passes through the stream channel.
	Bioaccumulate	Process which harmful substances move through the food chain, by one creature eating another, accumulating (at higher concentrations) in the top carnivores.
	BOD	Biological Oxygen Demand. It is a measure of how quickly organic matter can de-oxygenate the water. Water with high BOD figures is thus badly polluted. Lower figures are better.
	Brownfield site	An area of land that has already been built upon.
	Carcinogenic	A cancer producing substance.
	Culvert	An artificial drainage channel for transporting water quickly from place to place.
	Effective rainfall	The amount of water (from rainfall) left after evaporation has taken place.
	Evapotranspiration	The evaporation of precipitation from plants.
	Groyning	Solid structures which point into the sea. E.g. rocks, to prevent erosion of the coast.
	Infiltration capacity	The maximum rate at which water can enter the ground water table.
	Landfill leachate	Pollutants from landfills which soak through the soil enter the groundwater table and finally into the river.
	Levees	Artificial embankments made to protect areas against floods.
	Meteorological Office	An organisation that studies the weather in order to forcast future weather conditions.
	NNR	National Nature Reserves are protected areas of land designated by the British Government. They are designated to protect general ecological habitats.
	Oxygenation	The process of oxygen dissolving into a liquid (in this case from the air into the river).
	Pervasive	Easily spread throughout. e.g. Oil spreading on the surface of water onto animals and coastlines etc.
	Phytoplankton	Microscopic plants that live in open water.
	Relief	The differences in the height of land.
	SPA	Special Protection Areas are protected areas of land designated by the European Union under the Birds Directive.
	SSSI	Sites of Special Scientific Interest are protected areas of land designated by the British Government. They are designated to protect wildlife habitats, geological features and landforms.
	Sump	A low area into which liquid drains and collects.
	Tertiary rocks	Rocks laid down before the Quaternary (Ice Age) period and after the Secondary (Post Cretaceous - chalk) period.
	Toxic	A harmful or deadly substance.