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Significant Pressures: Peat
Peat extraction for commercial or domestic purposes, and modification or drainage of peatlands for other uses such as forestry or agriculture, has been identified as a significant pressure in 119 (8%) water bodies that are At Risk of not meeting their water quality objectives (Table 1, Figure 1). This is the sixth most prevalent significant pressure type in river water bodies.
Table 1: Number of At Risk water bodies with peat as a significant pressure
|Waterbody (WB)||Number of WBs||Number of At Risk WBS||Number of Wbs with peat as a significant pressur||% of WBs with peat as a significant pressure||% of At Risk WBs with peat as a significant pressure|
Impacts on water quality and habitat from Peat
The main impacts on water quality and river habitat arising from peat extraction and drainage include the release of ammonium and fine-grained suspended sediments, and physical alteration of aquatic habitats.
There is evidence from targeted water quality monitoring data that ammonium concentrations downstream of modified peatlands can be very high, and can exceed the environmental quality standard of 0.065 mg/l that is required to support Good Ecological Status. The mean ammonium concentration over the last cycle (2010-2015) in water bodies impacted by peat was 0.08 mg/l. We also know from the biological monitoring programme that there is excess suspended sediment in some places, which can build up on stream beds and clog stream gravels, impacting on fish spawning and invertebrate habitats.
Water bodies that are impacted by peatlands are most commonly at Moderate status for those waterbodies with an Environmental Objective of “Good” status and at Good status for those sites with an Environmental Objective of High status (Figure 2), however, the majority of ‘At Risk’ Waterbodies with Peat as a significant pressure have additional pressures associated with them.
How do the problems arise?
The most likely situations for generation of suspended sediment from peat are:
- Mechanised peat extraction where milling, drying and harrowing, and peat harvesting creates loose peat particles which can be washed and blown into streams;
- Installation of drainage channels in peat which results in flow pathways for sediment reaching water bodies; and,
- Erosion following heavy rainfall.
The ammonium arises from lowering the water table in the peat when it is drained, which breaks down the peat and releases ammonium. Further research is required to precisely understand this process, and the combined impacts of ammonium, pH and dissolved organic carbon on the aquatic environment.
Drainage of peatlands also results in changes to the hydromorphological condition of rivers, for example, modification of the channel bed and riparian area, river channel diversions altering the river network, increasing the connectivity of land drains to the river network, and altering the flow and sediment regime.
The mitigation actions for impacts from peatlands include the use of settling ponds to prevent sediment reaching stream channels, and blocking drainage channels and rewetting to prevent losses of ammonium and sediment, and improve hydromorphological condition. These actions also have multiple benefits for biodiversity, climate change and natural flood water retention.
Regulation of extraction
Large-scale peat-extractive industries from areas above 50 hectares are required to hold an Integrated Pollution Control (IPC) licence from the EPA for their activities. Bord na Móna currently owns or controls 7% of the peatlands of Ireland and is the largest peat extraction operator. Environmental Impact Assessment (EIA) and Appropriate Assessment under the Habitats Directive will be mandatory in the consideration of licence applications.
The Catchment Assessment Team will undertake Local Catchment Assessments in the Areas for Action to identify precisely which activities in peat are impacting water quality. They will work together with the operators of peatlands to implement appropriate mitigation actions. They will be guided by The National Peatlands Strategy which states as a principal that “Policies and decisions relating to the use of peatlands shall take full consideration of potential impacts on water quality and the attainment by the State of mandatory water quality standards”.
In addition, Bord na Móna have a Sustainability 2030 Strategy which addresses the long-term rehabilitation of its cutaway bogs. Many bogs will cease peat production for energy generation under these plans and will become available for rehabilitation. Bord na Móna expects to rehabilitate 9,000 hectares of cutaway bogs across 25 peatlands by 2021 and will look to implement best available measures to further reduce water quality impacts. These measures are expected to improve water quality over time in 12 associated water bodies.
There is on-going research into peatlands including ‘The Living Bog’ EU Life Project (2016-2020) which is focused on restoration and conservation of twelve raised bog SACs. The 2018 EPA Research Call also included a topic on evaluating mitigation strategies for improving water quality from drained peatlands.
Find out more:
You can view the individual water bodies where peat is a significant pressure on www.catchments.ie/maps
For planning and policy, including measures, see www.bit.ly/rbmp20182021