Download Hydrosphere Sample Answers

Hydrosphere Sample Answers
5b) Study and Reference Diagrams Q5A and 5B.
Mark 6
Describe and explain the changing river levels at Stratford-on-Avon between 5
and 13 April.
There is zero rain fall on the 5th and 6th April, then there is rain fall of up to 12
mm on the 7th and 8th April. However the river level remains steady at under 1
meter from the 5th to late on the 8th. This is due to rain infiltrating the soil
therefore not reaching the river.
The rain increases dramatically to 60mm on the 9 April then subsides to 4mm on
the 10th. The hydrograph shows a steep rising limb reflecting the water reaching
the river fairly quickly. The peak discharge in the river is over 2.8 meter on the
10th of April which is a lag time of only one day. The reason the water reaches
the river quickly may be due to a combination of any of the flowing factors: steep
slopes, many steams for drainage, little vegetation, mostly impermeable rock
type, or to be a small drainage basin.
From the 11th to 13th there is less than 2mm of rain each day. The recessing limb
declines gradually from the 11th to 13th with discharge only nearing its original
level of under 1 meter on the 13th. This is due to moisture from the heavy rain
reaching the river via through flow and base flow.
2005 Hydrosphere
6b) Describe and explain with the aid of a diagram or diagrams how a meander is
formed.
Mark 6
Meanders are formed by the processes of erosion and deposition. Water moving
to the outside of the bend encounters little friction and therefore has a faster
velocity. The force of the fast moving water hitting against the outer banks erodes
it by Hydraulic action. This is when the pressure of the water mechanically drags
away particles of lose material from the river wall. Also the water carrying
particles in suspension rub against the outside of the bend and erode it by means
of corrasion.
These eroded particles are transported to the inside of the next mender by
helicodial flow, the corkscrew like movement of the water. These particles are
deposited on the inside of the bend which creates a gentle slip-off-slope.
Particles are deposited because as the water encounters friction it’s velocity and
energy is reduced and it is no longer able to transport the particles.
As this process repeats over and over the meander migrates across the flood
plain.
Or
Water never flows in a straight line and the river bed is not an even surface. At
the upper and middle course of the river there will be deeper sections of the river
with fine sediment. This is called a pool, and the river will flow slower here. Water
will flow faster at riffles which are shallower parts of the river with larger bed load.
These pools and riffles cause the river to swing from side to side. The pools tend
to move to the opposite side of the river channel and this is where a meander will
develop. Riffles can be found at the straighter sections of the river channel.
The fast moving water has more energy to erode and will erode the outside of the
river channel where the pools are. It will do this by corrasion and hydraulic action.
On the other side of the bend deposition will occur and create a gentle slope
called a slip off slope.
As this process repeats over and over the meander will get bigger and will
migrates across the flood plain.
2006 Hydrosphere question 5
5a) A drainage basin is an open system with four elements – inputs, storage,
transfers and outputs. Describe the movement of water in the drainage basin.
Precipitation falls within the drainage basin, this is the input to the system.
This precipitation can be stored in surface storage such as lakes, lochs or on
leaves of vegetation. It will also be stored or below the ground as soil storage or
as groundwater in the pores and joint of permeable rocks resting on top of
impermeable rocks.
Water is transferred by overland flow: thoughflow, this is when water in the soil
moves underground in the direction of rivers and stream: and groundwater flow
which is the slowest of all water movement and can take up to years after
precipitation occurs to moves out of the system.
Initially precipitation falls on vegetation, this is called interception and reduces the
amount of water reaching the ground. Water is then transferred thought the top
layers of the soil by soil infiltration. It may be stored here as soil storage or
transferred out by though flow. Some water will be transferred by percolating
further down though permeable rocks.
Moisture can leave the sytem by evaporation form lakes and lock, or can be
transpred from