- Abstraction: Removal of water from rivers, lakes, canals, reservoirs or from underground strata.
- Inputs: Ways in which water can get into the system.
- Store: Ways of storing water in a drainage basin.
- Output: Ways in which water can leave the system.
- Flow: Mechanisms which allow water to move one place to another.
- Greenwater flow: interception and transpiration of water by vegetation or its evaporation from surfaces.
- Grey water: polluted water, excluding sewage.
- Infiltration: a process of water entering rocks or soil.
- Percolation: the filtering of water downwards through soil and through bedding planes, joints and pores of a permeable rock.
- Precipitation: the deposition of moistures from the atmosphere into the earth’s surface such as rain, hail, frost, sleet or snow.
- World water gap: the difference between those people who lives in water poverty and those who have ready and reliable access to water for drinking and sanitation.
- Stream flow: the flow of water in streams, rivers and other channels. Major element of water cycle and main mechanism by which water moves from land to oceans.
- Surface run off: the movement over ground of rainwater.
- Through flow: infiltration through soil.
- Desalination: the conversion of salt water into fresh water by the partial or complete extraction of dissolved solids.
- Over abstraction: the consumption of ground water and surface water beyond their sustainable level, gradually being depleted.
- Helsinki rules: 1996 international legal agreement on the fair use of international waterways used by two countries:
- Water security: the extent to which a region can secure sufficient reliable supplies.
- Water rights: the legal right of a user to use water from a water source.
- Water wars: international conflict because of pressure on water supplies.
- Water pathways: the routed taken between sources of water and where it will be consumed such as pipelines or artificial canals.
- Virtual water: water which is transferred by trading in crops and services which require large amounts of water for their production.
