Case study: the river Exe, Devon Flashcards
How far does the river Exe flow from its source to the coast?
82.7km
Where is the source of river Exe?
in the hills of Exmoor
Where does the river Exe reach the coast?
The south coast of Devon
Name 2 places that the river Exe pass through?
Tiverton and Exeter
How many km^2 is the area of the upper catchment of river Exe?
601 km^2
What is the maximum elevation of the upper catchment of the river Exe?
514 metres
What is the maximum elevation of the lower catchment of the river Exe?
26 metres
What % of the catchment of the river Exe is underlain by impermeable rocks?
84.4%
What % of the land around the river Exe is agricultural grassland?
67%
What % of the land around the river Exe is woodland?
15%
What % of the land around the river Exe is moors and peat bogs?
3%
Is rainfall high or lover at the river Exe?
high, particualy over Exmoor
What % of runoff accounts for the water balance?
65%, quite high compared to other UK rivers
What are the 2 reasons for runoff being high at the river Exe?
- the impermeable ground that reduces percolation and baseflow
- drainage ditches on exmoor reduces the amount of soil storage
What does the annual hydro graph of the river Exe show?
- that the river responds relatively slowly to rainfall events
- after flooding, the discharge recedes slowly, reflecting the rural nature of the lower catchment
Define river regime.
the pattern of discharge over the course of a year
What 2 recent development have effected the water cycle and balance at the river Exe?
- the construction of Wimbleball reservoir
- the restoration of peatland on Exmoor
What tributary of the river Exe was dammed to create the Wimbleball reservoir?
the river Haddeo
What year was the Wimbleball reservoir built?
1979
What is the surface area in hectares of the Wimbleball reservoir?
150 hectares
What is the benefit of the Wimbleball reservoir for the river Exe?
it regulates water flow, ensuring a steady flow regime during the year
Why were drainage ditches dug at Exmoor?
drainage ditches were dug in the peat bogs of Exmoor to
- make it suitable for farming
- to use the peat as fuel
What was the impact of the drainage ditches at Exmoor on the river Exe?
Increased the speed of water flow to the Exe which reduces the water quality as more silt is carried downstream into the river Exe
What was the impact of the drainage ditches on the carbon cycle?
as the peat surface dried out, decomposition occurred, releasing carbon from this important carbon store into the atmosphere in the form of carbon dioxide and methane
What was the Exmoor Mires Project?
to restore the peat bogs by blocking the drainage dithces with peat blocks or moorland bales
How many hectares of Exmoors peatlands did the Exmoor Mires Project aim to restore?
2000
What are the 5 benefits of the Exmoor Mires Project
- more water storage in upper catchments
- improved water quality
- more carbon storage
- improved opportunities for education, leisure and recreation
- improved grazing and water supply for animals
How many hectares of peatlands was restored by 2015 from the Exmoor Mires project?
1000
How much did the water table rise by from the 1000 hectares of peatlands being restored by 2015?
2.65 cm
As there is a large drainage density at the river Exe, what type of regime does it have?
flashy
