Case Study: Carbon Cycle - RIver Exe Flashcards
How far does the River Exe flow?
80km to the sea at Exmouth.
what is the water balance for the river Exe?
precipitation (1295mm) = evaporation +/- soil water storage (451mm) + runoff (844mm)
What is the average precipitation into the River Exe?
1295mm
What is the evaporation +/- soil water for the River Exe?
451mm
What is the runoff for the river Exe?
844mm
What percentage of preciptation runoff?
65%
Why is the runoff percentage quite high?
Area - 600㎢, source in hills of Exmoor, flatter in the south.
Geology - over 80% is impermeable rocks e.g. Devonian sandstones
Drainage ditches to drain peatlands reduce soil water storageHigh levels of precipitation
What is the area of land like around the River Exe?
600km2, source in hills of Exmoor, flatter in the south.
What is the geology like in Exmoor?
over 80% is impermeable rocks e.g. Devonian sandstones
What is an example of the impermeable rocks in Exmoor?
Devonian sandstones
Why is there a longer lag time
Land use - Almost 70% grassland, 15% woodland and farmland. 3% peat bogs
What is the percentage of grassland?
70%
What is the percentage of woodland and farmland?
15%
What is the percentage of peat bogs?
3%
What factors affect securing a sustainable water supply (&/or flooding) in a named catchment?
The River Exe catchment
Wimbleball Reservoir
Peatland restoration on Exmoor - Exmoor Mires Project
Which river runs through the Wimbleball Reservoir?
1979 River Haddeo, upland tributary, dammed to create Wimbleball Reservoir.
What is the surface area of Wimbleball Reservoir?
Surface area of 150ha
Where does the Wimbleball Reservoir supply water to?
Exeter and parts of East Devon.
What does the Wimbleball Reservior do?
Regulates water flow, flattening the regime, reducing risk of flooding or drought.
What has happened to peat bogs in Exmoor?
Drainage ditches have been built in the past to make peat bogs suitable for farming. However, this has increased speed of water flow to the Exe and reduced water quality carrying more silt.
What happens as peat dries out?
decomposition has taken place, releasing CO2 and CH4
What else is peat dug for?
Fuel
What has the mires project done?
restored peat bogs (mires) by blocking drainage ditches
What has replaced the ditches?
More water storage in upper catchments, ensuring steady supply of water through the year
What has resulted from the Mires project?
Improved water quality - slower flow means less sediment carried to rivers, good for salmon.
More carbon storage - water content increases and returns ground to saturated, boggy conditions. This helps to keep carbon in the peat.Improved opportunities for education, leisure, recreation.
Improved grazing and water supply for animals.
