Ecosystem Services Evidence Case Study EXMOOR MIRES ... · South West Water: million, but there is...
Transcript of Ecosystem Services Evidence Case Study EXMOOR MIRES ... · South West Water: million, but there is...
Ecosystem Services Evidence Case Study
EXMOOR MIRES, SOMERSET, UK
1o Ecosystem Service Driver:
Water regulation
Restoration and re-wetting of
upland mires slows flow rates and
supports more sustainable water
supplies from natural landscapes.
2o Outcomes & Benefits
Provision of fresh water
Climate regulation
Habitat provision
Beneficiaries & Service Buyers:
South West Water:
Private Company supporting
sustainable resource supply and
reducing operational costs
UK General Public:
As drinking water customers in the
South West Water region.
Service Seller:
Farmers & landowners on Exmoor
Intermediary:
South West Water
Broker
University of Exeter
Natural England
Environment Agency
English Heritage
Knowledge providers
Further Information:
South West Water:
www.upstreamthinking.org
www.southwestwater.co.uk
Water Supply from the Exe
The River Exe rises in the hills of Exmoor and its waters are used to supply
several towns and the city of Exeter in Devon. To ensure continued water
supply to these customers, in the 1970s South West Water built the Wimbleball
Strategic Reservoir in the headwaters of the Exe on the River Haddeo.
However, in recent years, with increasing demand, low rainfall and the possible
threats of climate change the water level in Wimbleball has dropped
considerably during recent summers posing a threat to the continuous supply
of water.
Assessing the prospects for trade
The Exmoor Mires Project represents a real opportunity to make a significant
difference by implementing sustainable hydrological management in upland
river catchments. Increased storage and retention times of surface waters
should result in local modifications to the existing hydrology with small scale
reductions in peak flows, elevated base-flows and reduced water velocities.
The buffering capacity of restored wetlands may contribute locally to the
reduction of environmental damage associated with extremes in flows. Topographical and thermal imaging analyses were undertaken to examine the
hydrological flow patterns in the upland peat areas and to identify the locations
of natural and non-natural drainage features. This allowed the currently wet
and dry peat areas to be identified and targeted to achieve optimal results.
The estimated cost of creating a second
reservoir to meet this challenge is
estimated to be in the region of £90
million, but there is a possible
alternative: the restoration of the peat-
land mires on Exmoor to reinstate their
water storage capacity. This approach
was estimated to cost just £5-10 million.
Hydrological
modelling
This research project also produced a
flow-path model using a Geographic
Information System to classify
channels and to produce
visual displays that support
decision making over hydrological
connectivity and which also highlight
other features e.g. of archaeological interest.
Rendered surfaces composite images of Moorland at Spooners Site illustrated as TABI/LiDAR/Hillshade composite
The initiative to restore upland mires and reverse the degradation of peat bogs
to optimise water storage capacity through natural hydrology began with a
pilot in 1998 run by the Exmoor National Park Authority and partners, and is
now in its second full working phase led by SWW.
Ecosystem Services Evidence Case Study
EXMOOR MIRES, SOMERSET, UK
Monitoring & Outcomes
The monitoring programme design, instigation and set-up, with delivery from
partners in the Environment Agency and Universities of Exeter and Bristol, has
progressed to the point where all the monitoring sites are now established.
The Flow Monitoring Flume construction and installation has also been
completed by the contractor AVQ Water Solutions.
The University of Exeter is carrying out extensive monitoring work, examining
hydrological functioning (i.e. water table depth, flow and seepage), water
quality (i.e. colour, dissolved and particulate organic carbon), gaseous fluxes,
vegetation composition and structure, before and after ditch blocking. The
work is taking place on two sites (Aclands and Spooners) representative of
upland peatland on Exmoor. On each site, three different drains and the exit
point of the catchment are closely monitored. This will provide the first
detailed evidence base quantifying the value of peatland restoration in terms
of water quantity, quality and carbon sequestration Secondary benefits & outcomes
The Mires Project is also expected to deliver secondary benefits.
(1) Water quality: through slowing of flow/run off and sedimentation
to channels and increases natural filtration of vegetated uplands.
(2) Carbon sequestration: peatlands are huge carbon stores, while
damaged areas release carbon dioxide (CO2) into the atmosphere
through oxidation processes. Restoration halts oxidation and
promotes active peat growth - increasing the absorption of CO2
from the atmosphere.
(3) Habitat provision: rewetting uplands reconnects fragmented
habitats, which may have been degraded or lost, by increasing
linkages within headwater ecological networks.
Delivery of interventions
A programme of ditch blocking has been undertaken using generally one
of two methods; either using baled rush or Molinia, or with peat/
vegetation taken from immediate area as backfilling to points ‘blocked/
dammed’ with timber. These were planned based on surveys (a total area
of 623 hectares and 64 km of ditches surveyed to date) and site
evaluation, as were mire restoration pools.
In the first project round (2006-10), on a budget of £400,000, a total of 50
km (4,300 ditch blocks) resulted in the re-wetting of over 350 hectares
across 17 sites.
Funds came from project partners and via Natural England’s Agri-
Environment schemes (HLS, ESA) for capital works on privately owned
moorland. The current project round is worth £2.4 million, and with
advances in technical surveying techniques has mapped a further 150
potential sites covering over 5,000 hectares. A grant for £150k has
successfully been obtained from the EA to support the ongoing
monitoring work.
Photo: L. B. Tettenborn