Case Study: Carbon Cycle - RIver Exe

Question 1

How far does the River Exe flow?

Answer 1

80km to the sea at Exmouth.

Question 2

what is the water balance for the river Exe?

Answer 2

precipitation (1295mm) = evaporation +/- soil water storage (451mm) + runoff (844mm)

Question 3

What is the average precipitation into the River Exe?

Answer 3

1295mm

Question 4

What is the evaporation +/- soil water for the River Exe?

Answer 4

451mm

Question 5

What is the runoff for the river Exe?

Answer 5

844mm

Question 6

What percentage of preciptation runoff?

Answer 6

65%

Question 7

Why is the runoff percentage quite high?

Answer 7

Area - 600㎢, source in hills of Exmoor, flatter in the south.
Geology - over 80% is impermeable rocks e.g. Devonian sandstones
Drainage ditches to drain peatlands reduce soil water storageHigh levels of precipitation

Question 8

What is the area of land like around the River Exe?

Answer 8

600km2, source in hills of Exmoor, flatter in the south.

Question 9

What is the geology like in Exmoor?

Answer 9

over 80% is impermeable rocks e.g. Devonian sandstones

Question 10

What is an example of the impermeable rocks in Exmoor?

Answer 10

Devonian sandstones

Question 11

Why is there a longer lag time

Answer 11

Land use - Almost 70% grassland, 15% woodland and farmland. 3% peat bogs

Question 12

What is the percentage of grassland?

Answer 12

70%

Question 13

What is the percentage of woodland and farmland?

Answer 13

15%

Question 14

What is the percentage of peat bogs?

Answer 14

3%

Question 15

What factors affect securing a sustainable water supply (&/or flooding) in a named catchment?

Answer 15

The River Exe catchment
Wimbleball Reservoir
Peatland restoration on Exmoor - Exmoor Mires Project

Question 16

Which river runs through the Wimbleball Reservoir?

Answer 16

1979 River Haddeo, upland tributary, dammed to create Wimbleball Reservoir.

Question 17

What is the surface area of Wimbleball Reservoir?

Answer 17

Surface area of 150ha

Question 18

Where does the Wimbleball Reservoir supply water to?

Answer 18

Exeter and parts of East Devon.

Question 19

What does the Wimbleball Reservior do?

Answer 19

Regulates water flow, flattening the regime, reducing risk of flooding or drought.

Question 20

What has happened to peat bogs in Exmoor?

Answer 20

Drainage ditches have been built in the past to make peat bogs suitable for farming. However, this has increased speed of water flow to the Exe and reduced water quality carrying more silt.

Question 21

What happens as peat dries out?

Answer 21

decomposition has taken place, releasing CO2 and CH4

Question 22

What else is peat dug for?

Answer 22

Fuel

Question 23

What has the mires project done?

Answer 23

restored peat bogs (mires) by blocking drainage ditches

Question 24

What has replaced the ditches?

Answer 24

More water storage in upper catchments, ensuring steady supply of water through the year

Question 25

What has resulted from the Mires project?

Answer 25

Improved water quality - slower flow means less sediment carried to rivers, good for salmon.
More carbon storage - water content increases and returns ground to saturated, boggy conditions. This helps to keep carbon in the peat.Improved opportunities for education, leisure, recreation.
Improved grazing and water supply for animals.