Peatlands for Water

Peatland plays a significant role as a water/carbon store and as a habitat. The island of Ireland has one of the highest concentrations of peatbog of any country worldwide, with 20% wetland coverage. In fact, approximately 68% of the island of Ireland’s drinking water comes from peatland, whilst up to 75% of its soil carbon is in the form of peat.

A key focus for the Source to Tap project was to investigate techniques for restoring formerly afforested peatland, which could be used to benefit drinking water quality in source drinking water catchments. Water from healthy, intact peat bogs requires less treatment, as it is well filtered by the Sphagnum moss. But when the bog is damaged, more carbon seeps into the water, colouring it and requiring costly treatment processes.

Greater quantities of sediment in our rivers and lakes also have an impact on freshwater habitats and water-dependant species.

Source to Tap piloted peatland restoration techniques from commercial forest back to peatbog.

Different peat restoration methods were trialled on a test site at Tullychurry Forest in County Fermanagh, owned by Forest Service (DAERA).

The restoration took place immediately after felling. The forest had been planted in a ridge and furrow pattern, creating pathways for water to escape, and so this needed to be addressed and water levels raised back up to prevent water from escaping from the site.

Download our Forestry Pilot Literature Review to find out more about current best practice for forestry post-felling peat restoration techniques and other techniques available to reinstate peat both on previously afforested sites and degraded bog sites.

Two methods were trialled: Cell Bunding and Drain Blocking

Cell Bunding (also known as Deep Trenching) is the construction of watertight ‘ponds’ called cells made from low peat walls, constructed at a 90-degree angle to the slope with a bund roughly every 30 cm fall in height.

‘Finger bunds’ are then constructed at intervals in line with the slope, joining the parallel bunds to prevent lateral erosion and wave action. Creating these watertight cells allows the water table to rise, encouraging the growth of Sphagnum moss.

Drain blocking with peat dams, is a popular method of peatland restoration. Peat dams were used to block drains and brash mats at 12 m intervals or every 30 cm drop in ground level. Dams were constructed using saturated peat from a borrow pit adjacent to the dam location.

Control area – The control area was designed to mimic existing forestry best practice when leaving a site to restore back to peatbog. In this area, drains were blocked with peat dams only where they exited the felled area.

Download our ‘How-to’ guide to Cell Bunding to find out more about their installation and their effectiveness.

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Sphagnum moss – the bog builder!

After the initial work to raise the water table, a 1 hectare section of the cell bunded area was sprayed with a mulch mix of sphagnum mosses to see whether this speeded up the process of recolonisation.

Sphagnum mosses play a vital role in the creation of peat. By storing water in their spongy forms, they prevent the decay of dead plant material and eventually form peat. Therefore, getting the conditions correct to encourage Sphagnum recolonisation was an important part of the restoration process.

Monitoring the success of restoration

Each of the three restoration areas (Cell bunding, Drain blocking, Control) were monitored using shallow groundwater dip wells.

These were sunk around 1.5 – 2 metres into the ground and used to monitor water table recovery post-restoration, and to collect water samples which were analysed for Colour and True Colour.

An area of intact blanket bog and an area of standing trees were also monitored for comparison with the three treatment areas.

Results

Cell bunding has been shown to work as a viable peat restoration technique for formerly afforested peatlands on flat terrain with deep peat. Biodiversity, water quality and carbon storage benefits are beginning to be realised through cell bunding and drain blocking using a series of peat dams (wave damming) at the Tullychurry Forest peatland restoration site, but further, long-term, monitoring is required to understand the recovery of the site over time.

Why not visit the site and see peat restoration in action?

You can visit the peatland restoration site for yourself at Forest Service (DAERA)’s Tullychurry Forest, near Lower Lough Erne, County Fermanagh. There is an interpretation panel on site that explains what has been done to help restore what was afforested land, back to peatland.

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