Case study the River Exe, Devon
Terms in this set (21)
What is the length of the River Exe?
Which towns does the River Exe run through?
Exeter and Tiverton
How would you describe the upper catchment of the River Exe
Extensive network of tributaries with a high drainage density
Describe the physical characteristics of the upper catchment of the River Exe
601 km^2 - north hilly with a max height of 514 m - south is flatter with an elevation of 26m
Describe the geology characteristics of the upper catchment of the River Exe
84.4% is impermeable sandstone
Describe the Land use characteristics of the upper catchment of the River Exe
67% agricultural grassland - 15% woodland and farmland - 3% moors or peat bogs
The water balance for the Exe catchment
P (1295 mm) = E + O (844 mm) +/- S (451 mm)
Why does runoff occur on the Exmoor?
Rainfall is high. Once ground is saturated or where drainage ditches have been dug water can flow off the hills rapidly
How much of the water balance if runoff
Why is runoff so high?
- Drainage ditches on Exmoor reduce the amount of water storage
- Impermeable bedrock
What does river regime mean?
The pattern of discharge over the course of a year.
Describe the annual hydrograph for the River Exe between 2012-13
What recent developments affect the water cycle on the River Exe?
1) The construction of Wimbleball Reservoir
2) Restoration of peatland on Exmoor
When was the Wimbleball Reservoir constructed and why is it important?
The RIver Haddeo was dammed in 1979 to create a reservoir of 150 ha.
It supplies and regulates water to Exeter and parts of East Devon. The regulation of supply means that there are not major peaks where large amounts of water is wasted.
Wimbleball plays an important role in the supply of water to the region, hence the term 'strategic supply area'.
Why does the peatland need restoring?
- Peat has been dug as a fuel
- Drainage ditches have been dug to make the area more suitable to farming
- As peatland drys out it release carbon from this important store in the form of CO2 and methane
How are the peatlands being resorted and what are the effects of this? (The Exmoor Mires Project)
Drainage ditches are being blocked using peat blocks or moorland bales. This keeps the ground saturated. This boggy, saturated ground is now able to retain the carbon stored in the peat.
What are the benefits of the Exmoor Mires Project?
- More water storage in the upper catchment
- Improved water quality
- More carbon storage
- Improved opportunities for education
- Improved grazing and water supply for animals
How has data been collected to assess the projects effectiveness?
- 3 experiment pools dug with dipwells transects created across the newly blocked ditches.
Describe the changes in the water table using the dipwell data
What were the results of the investigation?
- water tables started to rise (more moisture in the soil)
- Storm flow and peak flows are reduced.
What were the conclusions of the investigation into the Exmoor Mires Project?
The increase in the water tables seen reflect an increased storage of water in the peat mass following restoration and it is consistent with similar changes recorded in other re-wetted peatlands in the UK and Ireland (South West Water report 2012)
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