Water Cycle EQ1 Key Terms

• Orographic rainfall


  Concentrated on the windward slopes and summits of mountains.
• Convectional rainfall


  Often associated with intense thunderstorms, which occur widely in areas with ground heating such as the tropics and continental interiors.
• 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 vapour, clouds of different types and precipitation.
• Drainage basin


  The catchment area from which a river system obtains its supply of water.
• Storm hydrograph


  Shows changes in a river's discharge at a given point on a river over a short period of time (usually before, during and after a storm).
• Precipitation


  The movement of water in any form from the atmosphere to the ground.
• Processes


  The physical mechanisms that drive the flux of material between stores.
• Stores


  Reservoirs where water is held, such as the oceans.
• Precipitation


  The movement of water in any form from the atmosphere to the ground.
• Throughflow


  Water moving sideways through the soil, downslope under the influence of gravity.
• River regime


  The annual variation in discharge or flow of a river at a particular point or gauging station, usually measured in cumecs.
• Cryosphere


  Areas of the Earth where water is frozen into snow or ice.
• Percolation


  The transfer of water from the surface or from the soil into the bedrock beneath.
• Water budget

  The annual balance between inputs (precipitation) and outputs (evapotranspiration and channel flow) at a place.
• Surface run-off

  The movement of water that is unconfined by a channel across the surface of the ground. Also known as overland flow.
• Catchment


  The area of land drained by a river and its tributaries.
• Watershed

  The highland which divides and separates waters flowing into different rivers.
• Systems approach

  Systems approaches study hydrological phenomena by looking at the balance of inputs and outputs, and how water is moved between stores and flows.
• Infiltration


  The movement of water from the ground surface into the soil.
• Aquifer

  A permeable or porous rock which stores water.
• Blue water

  Water stored in rivers, streams, lakes and groundwater in liquid form (the visible part of the hydrological cycle).
• Green water

  Water stored in the soil and vegetation (the invisible part of the hydrological cycle).
• Evapotranspiration


  The combined effect of evaporation and transpiration.
• 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.