|What is a drainage basin?
|The area of land, bordered by a watershed, drained by a river and its tributaries.
|What is a watershed?
|The boundary of a drainage basin.
|What type of system is the hydrological cycle?
|A closed System.
|What is precipitation?
|Movement of water from the atmosphere to the earth surface in the form of rain snow or hail.
|How does precipitation lead to flooding?
|->Prolonged or heavy rainfall. ->Snow acting as a store of water then melting.
|What is overland flow?
|This is a rapid form of water transfer over the surface of the ground.
|When is overland flow most likely to occur?
|->During periods of heavy rainfall. ->When the soil has become completely saturated.
|What is infiltration?
|The movement of water from the ground surface into the soil.
|What affects the rate of infiltration?
|->The moisture content of the soil. ->The soils porosity. (number of air spaces)
|What is throughflow?
|The downhill transfer of water through the soil layer to the river.
|What is percolation?
|The movement of water from soil into permeable rocks.
|What is permeable rock?
|A rock which can absorb water (porous) or allow water to pass through cracks and joints (pervious).
|What is baseflow (groundwater flow)?
|This is the very slow transfer of water through rocks.
|When can groundwater/baseflow be faster?
|In limestone areas where there are extensive underground channels.
|What is the soil moisture of: ->Clay ->Sand
|->Poor. Clay soils can be very wet and boggy. ->Good. Sandy soils tend to be much drier so they absorb more precipitation.
|What is depression storage?
|When water is stored temporarily on the ground surface in the form of puddles.
|What is interception?
|Vegetation, particularly trees, stopping some precipitation on its way to the ground.
|What does vegetation do to water transfer and why?
|Vegetation slows it down. Some water is lost by evapotranspiration while some water is used for plant growth.
|What is evapotranspiration?
|When water loss from the ground surface to the atmosphere (evaporation) combines with water given off from plants (transpiration) to form a main output from the system.
|What is the water balance equation?
|P=O+E+/-S P=Precipitation O=Total run off(stream flow) E=Evapotranspiration S=Storage (in soil and rocks)
|What causes a high runoff percentage?
|->Lack of trees ->Saturated soil ->Impermeable rock
|What is impermeable rock?
|A rock which cannot absorb water.
|What causes a low percentage of runoff?
|->Lake (storage) ->Lots of trees. ->Dry soil ->Permeable rock
|What is river discharge?
|The volume of water passing a given point in a given period of time, usually expressed in 'cumecs' and calculated as: Cross sectional area x Velocity
|Factors affecting the discharge of a river.
|->Distance downstream ->Climatic changes ->Land use ->Water abstraction ->Channel modifications
|What is a storm hydrograph?
A graph that shows the discharge of a river following a storm event.
Image: images (image/jpg)
|Compare the characteristics of a typical river during low-flow conditions and a typical river during high-flow conditions have?
|A river during low-flow has clear water and a visible river bed while a river during high-flow has murky water and no riverbed visible.
|The amount of energy available in a river to do 'work' depends on...
|->The height the water has to descend (gravity) ->The mass of water available.
|When water starts to move downhill _______ energy is converted into ________ energy.
|When a water starts to move downhill potential energy is converted into kinetic energy.
|What is a load?
|The sediment carried by a river.
|What is solution?
|The invisible transport of chemicals dissolved in the water. Eg. Calcium carbonate.
|What is suspension?
|Very fine-grained mud and silt which is carried in the main body of the water. (makes the river look dark and murky)
|What is bedload?
|Larger sediments being transported along the riverbed, which is too heavy to be picked up and carried as a suspended load.
|What is traction?
|Material rolling along the river bed. Eg Boulders.
|What is saltation?
|Material moving in a series of small bounces along the riverbed. Eg. pebbles
|What is erosion?
|The picking up and removal of material.
|When does erosion occur?
|When the river has surplus energy available.
|What is abrasion?
|Where particles of rock carried by the river scrape away at the riverbed and banks. This can dislodge rock particles to add to the load of a river (sandpaper affect)
|What is hydraulic action?
|Where the power of moving water is able to dislodge loose particles of rock from the riverbed or banks.