Rivers Notes

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  • Created by: Emilie
  • Created on: 25-01-15 19:40
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The Drainage Basin Hydrological Cycle
The drainage basin is an area of land drained by a river and its tributaries. The hydrological cycle is
the process by which water is moved within the drainage basin. The drainage basin hydrological cycle
is an open system as water is gained and lost. The system is made up of:

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Vocab Definition
Precipitation Any form of moisture that falls to the Earth's surface (rain, sleet,
snow, hail). Acts as the major input into the system.
Evaporation The physical process by which water is changed into water vapour and
moisture is lost from the system.
Interception Where vegetation catches the precipitation before it can reach the
Throughfall Water drips through the leaves of a plant. Takes place after the
vegetation intercepts the precipitation.
Stemflow Water flows down the trunks or stems of plants.…read more

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Lag Time The period of time between the peak rainfall and peak precipitation in
the drainage basin. This varies according to conditions within the
Using a systems approach, explain how different components of the drainage basin hydrological
cycle are linked
(15 marks)
There are four main components of the drainage basin hydrological cycle: inputs, outputs, transfers
and stores.
The main input into the system is precipitation in the form of rain, snow sleet or hail.…read more

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If the soil is not saturated, then water will infiltrate (move vertically down through the soil). From
here it can be stored as soil moisture storage and if the underlying rock is impermeable (i.e. the
water cannot percolate) it can travel horizontally through the soil as throughflow and eventually join
the channel.…read more

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E > P from April to August (5 months). Evapotranspiration is highest in June/July.
3. Soil moisture recharge occurs as evapotranspiration decreases from October due to reduced
temperatures and less output when trees lose their leaves. P > E here and soil moisture
recharge lasts from October to February as evapotranspiration remains low and precipitation
is at its peak of 50+mm.
4. From February to April soil moisture surplus occurs because the moisture has been fully
recharged in the 5 pervious months.…read more

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A graph showing the variations in a river's discharge (in cumecs) over a period of time. There are two
types: flashy and steady. They show how a river responds to a rainfall event.
Factor Affecting Flashy Hydrograph Steady Hydrograph
Precipitation - Prolonged rainfall ­ soil becomes - If rain falls gently over a long period of
saturated so less infiltration and more time it encourages infiltration and
surface run-off occurs. increases soil moisture storage.…read more

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Thin soils are easily saturated, - A loam soil is best for storing water as
reducing soil moisture storage and it is a mix of sand and clay that
increasing surface run-off. promotes infiltration and storage.
Geology - Impermeable rock such as - Permeable or porous rock which
granite/slate prevents percolation and allows percolation and groundwater
groundwater storage. Therefore, soils storage leads to a steady hydrograph as
are saturated more quickly and water is slowly released as base flow.
surface run-off is more likely.…read more

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River processes
Erosion is the breakup of rocks by the action of rock particles being moved over the earth's surface by
water, wind and ice.
Rivers erode because they possess energy.…read more

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There are four main processes of river erosion:
Abrasion is the scraping and scouring of the load. It is most effective in short turbulent
periods such as when the river is in flood or at bankfull.
Hydraulic action is the force of the moving water. It is effective at dislodging loose grains
from the bed and banks, particularly in those of meanders which can then lead to
undercutting and collapse.
Corrosion (solution) is the dissolving of soluble particles such as limestone and chalk.…read more


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