Closing drainage ditches in River Pudisoo catchment in Estonia 鈥� why and how?

It is fair to say that each river is the result of its catchment. The water and sediment flow of the riverbed are directly affected by the character and the condition of the catchment. When we in Estonian State Forest Management Centre, RMK, want to improve the habitats of freshwater pearl mussels (FPM) in the only FPM river of Estonia, River Pudisoo, we cannot look past the issues we have with the catchment.
Closing drainage ditches in River Pudisoo catchment in Estonia 鈥� why and how?
Spring has arrived on the banks of River Pudisoo. (Photo: Mihkel J盲rveoja)

Extensive ditch network, especially in wetlands, is contributing negatively to natural state of the river. It is believed that during the construction of drainage systems, a lot of fine sediment was added to the riverbed. Each maintenance cycle and heavy rains will add even more. Drainage network will also amplify abrupt floods and the effect of droughts. The water will be removed from the landscape much faster than in natural conditions.

Closing the drainage ditches creates the prerequisites for the recovery of the natural water regime. This promotes the rearrangement of the vegetation and restoration of species characteristic to the local habitats. Wetlands in good condition act as natural cleaning filters and water reservoirs in the catchment.

In LIFE Revives project RMK will close ditches in two large wetland areas 鈥� Punsu (208 ha) and K玫nnu suursoo (1400 ha), which are also part of nature conservation areas. It is not very known fact, that a significant part of the former drainage ditches in Estonia is in the current protected areas. In the most strictly protected zones, there are more than 90,000 hectares of peatland forests, which are closer than 150 meters to the ditches (Figure 1).

Figure 1.jpeg

Planning for restoration is a long process. The entire area is examined: existing ditches and ditch embankments are mapped and measured, and their condition is determined. The movement of water in the landscape is primarily affected by the terrain, therefore the ground elevation model is used to determine the locations and sizes of the dams to be built (Figure 2). The planning process can take up to a year before it is possible to start with the first restorations. We are almost finished with the planning of Punsu area, and restoration work can probably start at the end of the year.

Figure 2.jpeg

We have already previously restored two abandoned peat-mining areas in Pudisoo river catchment 鈥� Viru (2013 鈥� 2019) and Hara (2013鈥�2016) fields.

See also a short film about our best practices in mire restoration in Estonia (English subtitles!):聽

Author: Mihkel J盲rveoja, LIFE Revives project coordinator in RMK