the river exe

Question 1

where is it?

Answer 1

• flows 82.7km from it’s source in hills of Exmoor to the sea at Exmouth, Devon

Question 2

characteristics of river exe- physical

Answer 2

• area of upper catchment= 600km^2
• max elevation= 514m
• land= much flatter south (lowest point=26m)

Question 3

characteristics of river exe- geology

Answer 3

• approx 85%= underlain by impermeable rocks (sandstone)

Question 4

characteristics of river exe- land use

Answer 4

• 67%= agricultural grassland
  15%= woodland + arable farmland
  3%= peatlands + moors (North)
• wide floodplains in middle course
• increased impermeable surfaces due to urbanisation in Exeter

Question 5

what is its water balance value

Answer 5

1295mm
- precip (1295mm)= evap +/- soil water storage (451mm) + runoff (844mm)

Question 6

water balance- where is there high rainfall

Answer 6

• high rainfall everywhere (particularly Exmoor)
  –> much absorbed by peaty moorland soils
  BUT if saturated/where drainage ditches have been dug, water can flow off hills rapidly

Question 7

water balance runoff + reasons for this

Answer 7

• runoff= 6.5% of water balance (which is high)
  –> main reasons for this:
• impermeable nature of the bedrock= less percolation + base flow
• drainage ditches reduce amount of soil water storage
• affected by recent developments (Wimbleball reservoir + peatland restoration on Exmoor)

Question 8

wimbleball reservoir- when was it created

Answer 8

1979

Question 9

wimbleball reservoir- surface area

Answer 9

150 hectares

Question 10

wimbleball reservoir- who does it supply water to

Answer 10

Exeter + East Devon

Question 11

wimbleball reservoir- what does it do?

Answer 11

regulates water flow= steady flow regime during the year –> controls discharge, prevents peaks + troughs during the year + prevents droughts + flooding

Question 12

peatland restoration on Exmoor- what has been happening for decades+ impacts of this

Answer 12

• for decades drainage ditches= been dug up in peat bogs of Exmoor to make it suitable for farming –> this has increased speed of water flow to River Exe = reduces water quality as more silts carried downstream
• peat= been dug as fuel= leaves ugly scars on landscape –> as past surface has dried out= decomposition occurs= releases carbon from important carbon store in form of CO2 + methane

Question 13

exmoor mires project- what does it aim to do

Answer 13

• aims to restore 2000 ha of Exmoor to boggy conditions
• works to restore the peat bogs by blocking drainage ditches with peat blocks/moorland bales

Question 14

exmoor mires project- impacts of restoring the peat bogs

Answer 14

increases water content + returns ground to saturated, boggy conditions that would naturally occur in moorland env.
–> these conditions help to retain carbon stored within the past

Question 15

benefits of exmoors mires project work

Answer 15

• more water storage in upper catchments- water is transferred flow= increase storage capacity + steady water supply during the year
• improved water quality- slower throughflow= less sediment carried into rivers= cleaner water, less expensive to treat + better for wildlife
• more carbon storage- peat= carbon store + peat growth= CO2 is naturally absorbed from atmosphere + stored
• improved opportunities for education, leisure, recreation
• peatland habitats= biodiverse with many species
• improved grazing + water supply for animals

Question 16

2015
how much peat moorland had been restored?
how many ditches blocked?
how much has the water table raised by

Answer 16

peat moorland restored= over 1000ha

ditches blocked= 100km of them

water table raised by 2.65cm= reduce water that drains by 2/3