Factsheet 4: WATER
The Exmoor Mires Project works with land managers, partner organisations and local communities to
restore damaged peatlands on Exmoor by blocking drainage ditches. Keeping the peat wet will help it
withstand climate change and help to restore the moor, protecting the landscape and historic past stored in
the peat for everyone to enjoy in the future.
Lanacombe, a few months post-restoration
Sustainable catchment management by water companies is becoming increasingly important in a country and
world where demands on our water resources are increasing. The Exmoor Mires Project is a partnership project
led by South West Water as part of their Upstream Thinking initiative. Of particular interest is the potential for
increased retention and improved quality of water running off the moor through mire restoration on Exmoor.
South West Water releases water from Wimbleball Reservoir into the River Exe to supply their abstractions at
Exeter and Tiverton during dry spells. Water needs to be pumped back up to refill the reservoir, but with
hotter summers and increasing demand threatening the constant supply of drinking water, costs are mounting.
The need to better understand the dynamics that peatland restoration plays in water management is vital to all of
us, now and into the future. The partnerships forged with the Environment Agency, the University of Exeter, the
Natural Environment Research Council and the Technology Strategy Board has started that process. They have
made it possible to expand our hydrological monitoring and research to include state of the art innovative
techniques and equipment. They have established an incredibly valuable resource that has given a detailed short
term picture of the hydrology of Exmoor’s peatlands, before and after restoration. Longer term monitoring is vital in
order to gain a fuller picture.
Hoar Oak Water
With thanks to the many volunteers, researchers, landowners, farmers and supporters of the Exmoor Mires Project
You can find out more about us at:
www.exmoormires.org.uk
Telephone: 01398 324491
Address: 7-9 Fore Street, Dulverton, Somerset, TA22 9EX
e-mail: [email protected]
facebook: Exmoor Mires
Centuries of moorland drainage for agricultural
improvement and peat cutting for fuel has dried
out Exmoor’s peatlands leaving them vulnerable
to future changes in climate. Functioning
peatlands sequester carbon but drainage makes
peatlands prone to erosion and oxidation
emitting the greenhouse gas carbon dioxide
(CO2) into the atmosphere. Rewetting raises the
water table and halts decomposition by oxygenfuelled microbes promoting further peat
accumulation and absorption of CO2 from the
atmosphere.
Eroding peat at Roostitchen
You can find out more about what we do at the Exmoor
Mires Project by picking up one of our other factsheets on
restoration, biodiversity, gases, hydrology, agriculture,
archaeology or mapping and remote sensing.
The Exmoor Mires Project is a partnership between the local community, farmers and landowners, the Exmoor National Park Authority, English Heritage, Natural
England, the Environment Agency and South West Water as part of the Upstream Thinking Initiative.
Drainage ditch ON Hoar Moor
www.exmoormires.org.uk
Drainage ditches rapidly channel rainfall off the
moor reducing the peatlands natural water
storage and buffering capacity. This leaves
downstream river reaches more susceptible to
storm spates or periods of low flow during dry
spells.
Research shows that mires store a third more
water after restoration, releasing water more
slowly into Exmoor’s streams and rivers.
Just as a sponge soaks up water, blocking up the
drainage ditches and peat cuttings should reduce
surges after storm events, contributing to
minimising flood damage and regulating the flow
of water running off the moors. The water is
naturally filtered as it slowly seeps through the
vegetated peat. The slower flow of water across
the landscape gives suspended particles in the
water more time to settle out, so we’d also
expect to see a a reduction of suspended
particles and dissolved organic carbon (DOC).
Monitoring Catchments
In partnership with the University of Exeter and
the Environment Agency, two automated
monitoring stations have been installed at
Aclands and Spooners restoration sites to
monitor and analyse pre- and post-restoration
hydrological data.
Water quality and flow rate is recorded at a trapezoidal flume in each catchment using automated flow meters
and water samplers connected via a mobile phone network to allow for remote activation in all weather. The
monitoring records what happens before, during and after storm surge events.
Water quality is tested for Dissolved Organic Carbon (DOC), nitrogen, phosphates, potassium, suspended
sediment, colour and pH at the University of Exeter laboratories. The height of the water table, seepage,
temperature and conductivity is also measured every 15 minutes by a network of dipwells. This can tell us the
effect restoration has had on re-wetting the mire as peat can only accumulate in waterlogged conditions (i.e. a
high water table).
The equipment set up includes:
 A weather station recording
rainfall, humidity,
evapotranspiration, wind and
temperature.
 Trapezoidal flumes armed with
automated flow meters and
pump samplers to measure the
flow rate, volume of water
discharged and water quality.
 Dipwells to measure the water
table height, temperature,
conductivity and water seepage.
Historical linear
mining feature
So far, we’ve collected over 13.1 million
bits of data.
Flow pathways
Initial
research
shows
that
mire
restoration has raised the water table by
an average of 2.2 cm at the Spooners
monitoring site. This is equivalent to an
increase of 110m3 of water stored per
hectare.
Water discharge and DOC after heavy
rainfall is a third less than it was before
restoration, indicating that water is
being retained for longer on the moors.
20931 litres of water = 3 tonnes of
water has been collected and carried off
the moor to be sampled by researchers.
Fence line
Drainage ditches
picked up by LiDAR
Square, tree bordered
Square, tree bordered
enclosure
enclosure
Wetness and flow patterns mapped
across the landscape at Spooners
Modelling the hydrology and flow patterns of
Exmoor’s mires using remote sensing, false colour
and aerial photography and Geographic
Information Systems has enabled the hydrological
connectivity of the landscape to be mapped.
Remote sensing is an effective way of surveying
large and spatially remote areas. The topography of
the landscape is closely connected to the
underlying hydrology, as water always flows
downhill. We use High-resolution Light Detection
and Ranging (LiDAR) to image the surface terrain
and model the flow of water across the moors.
Thermal Imaging (TABI) has not been used to map
peatland processes before, but has so far proved
promising in delineating wet and dry areas of peat
and other structural features.
These experiments aim to gain a greater
understanding of how mire restoration changes
the way water runs off the moor and how
effective ditch blocking has been in increasing
water storage capacity and improving water
quality. This is important to be able to assess the
provision of mire ecosystem services for
payment schemes to farmers and landowners.
A dipwell is a piece of plastic tubing
about a metre long and 3cm wide
with holes in the sides to allow
ground water to seep in.
Each
dipwell is sealed at the bottom and
stuck into the ground leaving 10cm
poking out. They are installed in a
grid-system with a water level
probe in each and wired up to the
central data logger.
Ongoing aerial surveys post-restoration enables
changes in the hydrology of each catchment to be
monitored. By extrapolating the findings from the
monitoring catchments will help to develop
predictions of hydrological function on a moorland
scale and quantify the value of peatland restoration
in terms of water quantity, quality and carbon
sequestration.
Pinkery Pond
www.exmoormires.org.uk