River Exe - Water Cycle

Question 1

The River Exe General Facts

Answer 1

82.7km from its source in the hills of Exmoor, through Tiverton and Exeter, to Exmouth on the south coast of Devon.
High drainage density.

Question 2

Characteristics of the Exe Upper Catchment

Answer 2

Physical - Upper catchment are of 601km squared.
- Max elevation is 514m
- Minimum elevation is 26m
Geology - 84.4% (estimation) of the catchment is underlain by impermeable rocks (predominately Devonian sandstones)
Land use - Most of the land is agricultural grassland (67%)
- Woodland (15%) and arable farmland
- Moors and Peatbogs (3%)

Question 3

Water Balance

Answer 3

Rainfall is high over Exmoor, most absorbed by the peatland - saturated land or dug-out drainage ditches can increase rapid runoff down hills.
Runoff accounts for 65% of the water balance (relatively high compared to UK rivers). This is because 1 the impermeable nature of the river reduces baseflow and percolation, and 2 drainage ditches on Exmoor reduce the amount of soil water storage.

Question 4

Developments Affecting the Water Cycle

Answer 4

Wimbleball Reservoir
- 1997, the River Haddeo (an upland tributary) was damned to create the reservoir.
- It covers a surface areas of 150 hectares.
- The reservoir supplies water to Exeter and parts of South Devon.
- It regulates water flow and ensures a steady flow throughout the year. It makes floods and droughts less likely.
Peatland Restoration on Exmoor
- Drainage ditches have been dug for agricultural purposes, which has inadvertently increased water speed flow to Exe, reducing water quality.