river Exe

• background

  • South west England flowing through Devon and somerset
  • approx 82.7km long
  • topography is much flatter in the south
  • mostly Devonshire sandstone and 84% of catchement impermeable rock
  • varied soil with areas of peat bogs
• land use

  • 67% agricultural grassland
  • 15% woodland
  • arable farming
  • historical deforestation but recent afforestation initiatives
• hydrological regime

  • seasonal variation in discharge with higher flows in winter
  • high precipitation and impermeable geology leading to high run off
  • high rainfall but absorbed by peaty moorlands but if saturated or drainage ditches dug water can flow rapidly
  • runoff accounts for 65% of water balance due to impermeable bed rock reducing percolation and base flow
  • drainage ditches reduce soil water storage
• hydrograph

  • Exe responds slowly, reflecting the rural nature of the lower catchment
  • 82% of land woodland or grass
  • shows river regime
• Wimble ball reservoir

  • completed in 1979 by damming a tributary
  • surface area of 150 hectares
  • supplies water to Exeter and parts of Devon
  • regulates flow ensuring a steady flow regime throughout the year
  • prevents peaks and troughs of water discharge which makes flooding and droughts more likely
  • recreational opportunities
  • modifies flow regime, reduces flood risk down stream and alters sediment transport
• Peatland restoration - Emoor Mires project

  • drainage ditches been dug for decades in peat bogs for farming
  • icncreased speed of flow reduced water quality and more silt is carried downstream
  • peat has been dug to use as a fuel
  • aim - restore 2000 hectares of degraded peatlands to enhance water storage and co2 sequestration
  • block drainage ditches to re saturate peat bogs with peat blocks or moorland bales
  • increased water storage, slowed runoff, raised water table
  • reduced carbon loss from peat decomposition
• benefits of peatland restoration

  • increased storage capacity
  • improved water quality as slower flow so less sediment carried
  • more co2 absorbed by peat bogs
  • used for education, leisure, recreation
  • improved all year round grazing and water supply
  • 2015 - 1000 hectares of peat moorland restored, 100km of ditches blocked, water table raised by 2.65cm, water drained from monitoring area reduced by 2/3
  • scientific research done on impact of peat restoration on water table
• data collection

  • 3 stations with dipwell transects across newly blocked ditches
  • electric dipmeter records depth of water table
  • showed water table started to rise meaning soil is retaining more moisture
  • storm flow and flood peaks reduced and baseflow increased
  • South west water report 2012 - increase in water table reflects increased storage of water in peat mass following restoration and other re wetted peatlands