River exe

• How long is the river exe?

  82.7km
• What Urban areas does the river Exe flow through?

  Exeter and Tiverton
• Land use of the catchment zone

  - 67% agricultural grassland

  - 15% woodland
• Why does surface runoff account for 65% (way above average) of the water balance?

  - most of the rock is impermiable so their is no infiltration

  - drainage ditches on exmoor reduces the soil water storage
• Wimble ball reservoir


  - 150 hectares

  - dam made in 1979 on the river haddeo (a river ex tributary

  - The dam prevents peaks and troughs preventing floods and droughts
• Why does digging drainage ditches on Exmoor have a negative effect?

  - Increases speed of water flow in the area making the catchment area at risk of floods and droughts

  - This increased speed of flow also lowers the water quality as more silt is carried downstream
• How much did the water table increase after the peatland restoration project?

  2.65 cm
• How many km of drainage ditches have been blocked?

  100km
• When was their heavy rain?

  December 2012 - 85.8mm rain fell in 24hrs
• What happened in 2018?


  Drought in July

  average temp of catchment = 24c

  Only rain on 3 days of the month
• what happened in 1979?

  Wimbleball reservoir built on tributary. Surface of 150 hectares
• What are the deforestation stats for the river Exe catchment

  10000 years ago almost entirely forested

  Now only 15%
• What project took place on exemoor

  Mires Peat restoration
• What did the mires peat restoration do?

  Drainage ditches were filled with peat and straw and covered in soil
• Why was the mire peat restoration project needed?

  large drainage ditches dug for agriculture drying out what would be a boggy area
• How much land was restored and how much did the water table rise as a result of this?

  over 1000 hectares

  Water table rose by 2.65cm
• What were the benefits of the Mires project?

  More water storage in upper catchment

  Improved water quality

  More carbon storage

  Improved opportunities for education

  Improved biodiversity

  Improved grazing and water supply for animals
• Why is is improved water storage beneficial in general?

  water transfer is slowed, storage capacity rises, causing a steady supply of water through the year - avoids plant loss during deficits
• Why is improving water storage beneficial to peat?

  More water ensures wet peat - ensures anaerobic conditions so that matter isn't broken down and carbon isn't released
• Why Is improved water quality beneficial?

  slower throughflow means less sediment is carried into rivers, water is cleaner, less expensive to treat and good for wildlife such as salmon
• Why is more carbon storage good?


  Peat is a carbon store

  Dry peat releases carbon dioxide through oxidation

  re-wetting the peat means carbon dioxide is absorbed from the atmosphere and stored
• What is the maximum elevation in the river exe catchment

  514m
• What is the area of the upper catchment?

  601 km2
• What is the geology of the upper catchment?

  Impermeable sandstone - 84% impermeable rock
• what are the % land uses of the catchment

  67% agricultural grassland

  15% woodland and arable farmland
• what is the minimum elevation of the catchment?

  26m
• What is the drainage density?

  Extensive tributary network
• how much rainfall is there every year in the exe catchment?

  1295mm