AS AQA Geography- Rivers

Flashcards by , created almost 5 years ago

Flashcards on AS AQA Geography- Rivers, created by hannah3g on 11/13/2014.

Created by hannah3g almost 5 years ago
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Question Answer
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. images.jpg (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.