water and carbon cycles CS 2( river catchment/ drainage basin- river Exe) Flashcards
where is the river Exe?
source Hills in Exmoor, through Tiverton and Exeter to sea at Exmmouth
how long is the River Exe?
82.7km
name 3 physical characteristics of the River Exe?
- area if upper catchment 601 km
- max elevation 514m in N
- lowest elevation 26m in S
what are the 2 geology characteristics of the river?
- 84.4% of catchment is underlain by permeable rocks
- predominantly Devonion sand stones extensive drainage works
what are the 4 land use characteristics?
- 67% argi land
- 15% woodland
- 3%of exmoor/peatbogs
- arable farmland
what is the water balance equation for the river?
precipitaion (1295mm)= evaporation+/- soil water storage (451mm) + surface run off (844mm)
what is the water balance over exmoor?
increased rainfall
what happens to the rainfall over exmoor?
much absorbed by peaty soils
what is the cause for water to flow of hills rapidly over exmoor?
drainage ditches or saturated land
what are the 2 reasons for ‘runoff accounts for 65% of WB increase?’
1) imperbale nature of bedrock= reduced percolation and base flow
2) drainage ditches on exmoor reduce amount of soil water storage
what were the two developments?
- construction of wimbleball res
- restoration od peatland on exmoor
how was the reservoir created?
1979 river haddeo (upland trip of river exe) was dammed to create WR
what is the surface area of the res?
150 her
what are the two main aims of the res?
- supplies water to Exeter and parts of east Devon
- regulates flow, ensure steady flow of regime during year (prevents peaks and troughs that make flooding more likely)
why was there a peatland restoration scheme?
drainage ditches dug in peat bogs so suitable for farming= ^ speed of water flow to exe= reduces water quality & more silt carried down stream
