Case Study: River Exe

• High drainage density :

  more streams & rivers per unit area
• River Exe Location :

  . Source : Hills of Exmoor

  . Sea : Exmouth , South coast , Devon

  . 82.7km

  . runs through Exeter

  . high drainage density

  . extensive tributary network

  . upper catchment above Thorveton Gauging Station (annual hydrograph📈📉 shows Exe responds slow to rain)
• Upper Catchment characteristics :

  1. Physical
  2. Geology
  3. Land Use
• Physical Characteristics:

  . 601km$^2$ area

  . North max elevation : 514m

  . South low elevation : 26m
• Geology Characteristics :

  . 84.4% underlain by impermeable rock : Devonian Sandstone
• Land Use Characteristics :

  . 67% agricultural grassland

  . 15% woodland

  . 3% moors & peat bogs (source)
• Water Cycle & Balance of Catchment effected by 2 developments :

  1. Wimbleball Reservoir
  2. Peatland Restoration on Exmoor
• Wimbleball🎾 Reservoir :

  . 1979 : River Haddeo (tributary) damned = reservoir

  . 150ha

  . supplies water to Exeter & Devon

  . regulates water flow = steady flow regime = prevents discharge peaks & troughs = decreased flooding & drought
• Peatland Reservoir on Exmoor :

  . aim : to restore 2000ha peat bogs by blocking ditches with peat blocks = restores saturated conditions = retains C stored in peat

  . drainage ditches dug in Exmoor for farming = increased water flow = silt = reduced water quality

  . peat dug for fuel = scarred & dried out = decomposition = $CO_2$&$CH_4$
• Peatland Restoration on Exmoor advantages :

  ✅slower through flow = less sediment into rivers = cleaner = less cost 💲to treat & better for wildlife (salmon🐟) & livestock🐑 water supply

  ✅more Carbon storage : dry peat releases C (oxidation) but rewetting + active peat growth = increases C absorption & storage
• River Exe Water Balance :

  . High rainfall 1295mm absorbed by peaty soil

  . Saturated soil + drainage ditches = rapid runoff (65%)

  . Impermeable bedrock = ⬇️percolation

  . Drainage ditches = ⬇️ soil water storage
• River Exe Data Collection :

  . measured effects of 2 projects on water table by installing dip well transects along blocked ditches - measured depth

  . results : water tables rose = increased water storage in peat following restoration (consistent with UK & Ireland)
• groundwater store includes soil storage
• The Ganges River basin differs significantly from the River Exe basin in terms of size, climate, population density, pollution, and management. While the Exe benefits from a smaller, less populated catchment area and better infrastructure, the Ganges faces immense challenges due to its vast, densely populated basin and severe pollution and flooding risks. The scale and complexity of managing the Ganges basin are far greater, requiring significant improvements in infrastructure, pollution control, and flood management