3.1.1.6 River exe Flashcards
(20 cards)
Where is the river exe?
South west England, Devon
How long is river exe source to mouth?
82.7km
What type of bedrock accounts for 84.4% of the River Exe catchment?
Devonian sandstone which is impermeable
Max elevation north?
514m
How many km2 is the upper catchment?
602
15% of land in the catchment is used for what?
arable farmland for crops.
What area is the area were gonna look at?
Thorveton
What two developments in the river exe has affected the water cycle?
wimbleball resouvioir
drainage of peatland in exmoor.
how was wimbleball resouvoiur made?
1979 river haddeo was dammned and is 150ha
Why was peat dug out for what 2 uses?
Soil and fuel logs
Negatives of peat being drained?
Increased the speed of water flow back into river exe. Inc soil erosion and more silt to be carried.
What does the drying of peat surface lead to due to drainage?
as peat surface is dried out decomposition happens which means carbon and methane is released contributing to global warming.
What is peat good for and what happens when it’s removed.
Peat is a store of water in terms of soil moisture.This increases lag time and slow the rate of return
When peat is drained surface run of increases which means the lag time decreases as water flows into drainage ditches insead of throughflow. This increases the chance of flooding due to water rapidly leaving the system.
Drainage ditches lead to soil erosion so more silt is enters the river channel leading to sediments being deposited. This leads to the river bed being increased and less capacity to store water increasing the chance of flooding. It also decreases the quality of water which may mean heavy reliance on chemicals to treat water.
What is the exmoor mires project?
They restore the peat bogs by blocking the drainage ditches with moorland bales or peat blocks to increase water content and saturation. This is to absorb carbon dioxide as the bog accumulates. Also allows plants to grow such as sphagnum moss which can store alot of water and filters water putting better quality water into the river.
How much mm of peat grows in healthy conditions and how much co2 is that stored
a tonne per mm of peat a year stored.
Aim of the project?
To restore 2000 ha of Exmoor to natural boggy conditions with peat and moorland bales.
Achievments:
2015 1000 ha of peat moorland has been restored and nearly 100km of ditches blocked raising the water table by 2.65cm
Why is raising the water table by 2.65m a massive positive.
It improves soil moisture for crops
keeps peat wet and allows more absorption of Co2 reversing the effect os peat drainage .
Filters water .
What type of sampling was used on here?
Stratified - A group or type of sample picked out on purpose e.g. the attitudes of 16-25 year olds on a soap opera
SEE positives
Social gains: Consistent and cleaner water supply for residents in the area and reduced risk of flooding (although higher baseflows)
Economic gains: water is of higher quality so easier to treat (costs less money) and can be used for more purposes eg: agrictulture.
Environmental gains: areas is restored to natural state – less carbon released contributing to global warming (global scale) and more consistent river discharges so less disruption to river wildlife systems (plants and animals)
