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