River Exe, Devon case study

Question 1

Where is the River Exe

Answer 1

Source in hills of Exmoor to sea at Exmouth on south coast of Devon

Question 2

Characteristics of upper catchment

Answer 2

Physical- maximum elevation 514m in north, flatter in south- lowest is 26m
Geology- 84% of catchment is impermeable rocks, mainly sandstone, explain the extensive drainage network
Land use- most of land is agricultural grassland, some woodland. High ground of Exmoor there are moors and peat bogs

Question 3

Water balance for river Exe catchment

Answer 3

High rainfall over Exmoor, much absorbed by peaty moorland soils
If saturated or drainage ditches, can flow off easily
Runoff is 65% (this is high), due to impermeable bedrock (reduces percolation and baseflow), drainage ditches reduce amount of soil water storage
Exe responds slowly to rainfall events

Question 4

Two recent developments affecting river Exe water balance

Answer 4

Construction of Wimbleball Reservoir
Restoration of peatland on Exmoor

Question 5

Wimbleball Reservoir

Answer 5

1979, tributary to Exe was dammed to create Wimbleball Reservoir
Supplies water to Exeter and parts of East Devon, regulates water flow and ensures steady flow of water all year- prevents floods or droughts

Question 6

Peatland restoration on Exmoor

Answer 6

Drainage ditches were dug into peat bogs (increased speed of water flow to Exe, reduced water quality as carried more silt)
Peat been dug into for fuel, as surface dried out decomposition occurred, releasing carbon
Working to restore peat bogs, increases water content so transfer slowed, better water quality as slower throughflow
Raised water table by 2.65cm (that’s good)
Storm flow and flood peaks reduced, baseflow increased