The River Exe

Question 1

source and mouth of the river

Answer 1

source - exmorr national park
mouth - exemouth

Question 2

river length

Answer 2

96km

Question 3

annual rainfall of upper + lower catchment

Answer 3

upper - up to 2000mm
lower - 800-1000mm

Question 4

geology

Answer 4

84% underlain by impermeable rock creating high SR
- lower catchment is more permeable

Question 5

releif

Answer 5

• maximum elevation = 514m
• lowest elevation = 26m
• land is much flatter in the south

Question 6

land use %of grassland + woodland)

Answer 6

• 67% agricultural grassland
• 15% woodland

Question 7

water balance

Answer 7

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

Question 8

what % of the water balance is runoff accounted for and what are the reasons for this

Answer 8

65%
- impermeable nature - bedrock reduces percolation + baseflow
- drainage ditches on Exmoor reduce amount of soil water storage
- much of rainfall is absorbed by the peaty moorland soils. when this becomes satuarated runoff increases

Question 9

where is the Wimbleball Reservoir loacted and when was it constructed

Answer 9

• located on the River Haddeo, a tributary of the upper catchment
• constructed in 1979

Question 10

area of the Wimbleball Reservoir

Answer 10

150 hectares, one of the largest in SW England

Question 11

role of the Wimbleball Reservoir

Answer 11

• supplies water to Exeter + parts of east Devon
• acts as a major water store holding approximately 21 million m³
• ensures steady flow and prevents peaks + troughs of discharge

Question 12

how does the Wimbleball Reservoir alter the natural water balance

Answer 12

• in the winter when rainfall exceeds evapotranspiration, it stores surplus water
• in the summer when evapotranspiration exceeds rainfall, it releases stored water

Question 13

positves of the Wimbleball Reservoir

Answer 13

• maintains river flow during drought
• acts as a store to reduce the risk of flooding
• supports aquatic ecosystems during low-flow periods

Question 14

negatives of the Wimbleball Reservoir

Answer 14

• flooding of farmland + habitats during construction
• changes sediment transport + river ecology
• extreme rainfall can exceed storage capacity

Question 15

when did the Exmoor mires project begin and who it led by

Answer 15

begain in 2010
led b y the Exmorr national park authority

Question 16

aims of the Exmoor mires project

Answer 16

aims to restor 2000ha of Exmoor back to boggy conditions by blocking drainage dithces with peak blocks + moorland bails

Question 17

why are drainage ditches bad

Answer 17

the lower the water table + increase surface runoff, increase downstream flood risks, cause drying of peat and carbon loss

Question 18

why are boggy conditions with more peat bogs better

Answer 18

peat acts like a sponge increasing water storage
- it reduces SR + increase lag time
- it improves the water balance with more water retained soils
- they are major stores of carbon and prevent release of CO2 if not dried out

Question 19

benefits to the Exmoor mires project

Answer 19

• increase storage in upper cathcment
• transfers are slowed + more steady throughout the year
• improved water quality - slower throughflow means less sediment in rivers
• increases carbon storage
• improved opportunity for education, leisure and recreation
• improved grazing + water supply for animals

Question 20

limitations to the Exmoor mires project

Answer 20

• has limited effect during extreme rainfall
• only affects part of the river catchmenmt - small spatial scale
• requires ongoing maintanance
• dry peat releases CO2 through oxidation