C1 Restoration of hydrological regime

Restoration activities in Soomaal. Photo: Jüri-Ott Salm

Main reason of the wetland degradation at the project sites is drainage – it directs and enchances water flow out of the wetlands. Closing off the drainage network is absolutely paramount for any kind of wetland restoration.

All drainage network within the project areas will be closed by various methods, specified during the formulation/updating of the restoration plans and technical designs (Actions A1 and A2).

The length of the drainage ditches in the restoration area reach approximately 240 km (Feodorisoo mire 13 km; Tudusoo 65 km; Laukasoo 38 km; Ohepalu 6 km; Soosaare 16 km; and Sirtsi 91 km; additional not mapped app 11 km). Please see added maps of project areas for details.

In the course of implementation of the restoration activities, the project team follows also guidelines from handbook “Ecological restoration in drained peatlands – best practices from Finland” prepared by Finnish agencies Metsähallitus – Natural Heritage Services and Finnish Institute SYKE in 2014.

To restore the habitats hydrology, the most used method will be continuous infilling of ditches with peat from adjacent areas. In addition,  supporting dams may be used, especially in areas with steeper slopes and stronger/larger water flows. Dams will be used also in area without reasonable thickness or quality of peat. Peat dams will be used where possible as on-site, natural material is available and those dams can be quickly built by excavator. Experience from similar projects from Latvia and Finland indicate abovementioned solutions as most cost effective restoration measures.

The sequence of infilling ditches and building of dams is following for all the project sites:

– Preparatory work for dam building and infilling ditches – marking the road for the excavator to reach the restoration area; if necessary, removal or cutting of trees is planned along the access road and ditches;

– Marking the dam building points in the field according to the Restoration Plan and Tecnical Design;

– Marking the areas for taking peat (remaining as small water bodies suitable for Rana arvalis (amphibian), Leucorrhinia dragonflies (semi-aquatic invertebrates)) for infilling ditches;

– Building of dams in accordance with the approved Technical designs and/or infilling the ditches;

– Levelling of the former ditch sides and removal of any temporary structures.

Manual work will be applied only in the places that are not accessible by the excavator. For example, wooden dams will be built by hand if peat of sufficient volume or quality is not available on site.

Peat and wood-peat dams will be built by hand using the methodology elaborated in other restoration projects in Estonia, also it is relevant to gather information from other restoration projects, e.g.  LIFE project sites in Latvia, Finland and Sweden. For this purpose study tours to these countries are of crucial value (Action E1).

Volunteers are involved into dam building activities in remote areas as well as in the case of small ditches (e.g. the case of Soosaare mire). ELF has  over  20 years of experience of organizing volunteer camps and they serve important educational and informative value besides actual work being done. Special activity is determined for this action (C3).

Manipulations of the tree cover. In some cases, drainage has led to considerable increases in tree cover in naturally open or sparsely wooded mires. Removal of tree cover reduces evapotranspiration which could considerably drop water level in the ground, making tree cover additional vector of the water loss from wetland. Therefore, in some cases only closing the ditches in not enough to bring water levels close to natural state for mire habitats and additional measures, concerning a thick tree cover must be implemented. Also, removal of tree cover restores more natural light conditions that favor the establishment of Sphagnum moss cover – a key component of the northern boreal mires, and otherwise helps the landscape to revert to a near natural state more rapidly. Proper actions regarding to the tree cover will be planned together with a research team from Tartu Un., State Forest Management Centre (RMK) and Environmental Board. The action itself if necessary – cutting and removal of trees from the restoration sites – will be carried out and coordinated by RMK. Relevant agreements have been made in a planning stage of this project.

Restoration actions will be implemented by different private companies recruited via public tendering. The companies should preferably have previous experience on restoration actions in peatlands, experience of building dams. In addition, definite licenses for working in amelioration works should be provided by the company.

During the duration of LIFE project, the maintaining of dams in the project sites will be the responsibility of the private company which has built the dams. ELF experts will check the condition of the closed drainage systems after each spring flood during the project. Remotely controlled aircraft with high quality camera  and on foot visits will be used for such surveys.

In the 1st phase restoration will be started in abandoned peat mining fields and it is scheduled that restoration work will be finalised in Sirtsi and Soosaare mires (in total 130 ha) by autumn 2017. If licencing for restoration with relevant restoration and technical plans runs smoothly there is chanche that more areas could be restored by then. It is expected that restoration in other project areas could start also in 2017 and lead to restoration of 50% of project areas by autumn 2018.  Hereafter it is expected that majority of work will be finished by the beginning of summer in 2019 and that the results of inspection and monitoring in spring  and summer 2019 will not imply the need for major additional actions. Still, if it is needed, there is time for repair work in 2nd phase of 2019 and 1st phase of 2020.