Background At the end of the last Ice Age, some 10 000 years ago, extensive peat bogs developed where the border between the Netherlands and Germany is now. After the bogs around Amsterdam, Utrecht and Haarlem had been dug up for peat production, layers of peat further inland were exploited. Thus large quantities were cut in the Korenburgerveen (Korenburg peat bog) in the east of the country. The original raised bogs and fens here, coupled with a wide variation in cutting methods from place to place, gave rise to a very complex hydrological situation, with local outflow or inflow of groundwater or rainwater and broad fluctuations in the water table. Besides ombrotrophic peat bogs, the Korenburgerveen also contains marsh birchwoods, eutrophic willow woods, wet heaths and, in seepage areas, acidic grasslands with an abundance of species. The conservation NGO Natuurmonumenten bought 94 ha of land in the Korenburgerveen as early as 1918, but the living peat bog largely disappeared as a result of a drop in the groundwater level in the surrounding farmland and an influx of nutrient-rich water. Since the mid-1980s, a management plan has been in operation. By exchanging plots of land, Natuurmonumenten has built up a consolidated block, which which has enabled the consistent hydrological management of this area. Objectives In co-operation with the other two owners of this area (the municipality of Winterswijk and the Vragenderveen Foundation), Natuurmonumenten launched a large-scale hydrological restoration project for this area. Support from LIFE Nature would make it possible to carry out the final parts of this project. The LIFE Nature Korenburgerveen project comprised a complex set of measures to dam or deviate water, in accordance with on-site requirements, in order to allow certain ecological communities to develop anew. For example, around significant areas of active bog, wooden barrier walls would be sunk into the ground to dam up the water and thereby allow the raised bog ecological communities to regenerate and expand. Another project action would see the restoration of the original profile of the Schaarsbeek (one of the main streams in the area), which would create a stronger flow in places and prevent pollution caused by groundwater runoff from adjacent farmland. Specific project actions would include: The construction of dams through the peat layer in the Vragenderveen to increase the water level so as to improve hydrological situation of mire core area; Placement of a levee in the Dal van de Schaarsbeek ditch to increase the water level and reshaping of the river profile to reduce the speed of the current; The construction of dams through the fen peat layer in Pollendijk to maintain the water level but to reduce seepage – a measure to improve the hydrological situation of the mire core area; and The construction of dams through the peat layer in the Corlese Veen to increase the water level so as to improve hydrological situation of mire core area and to integrate this with the level of the Schaarsbeek. Results The project actions have taken place as planned and additional measures have also been carried out. Specifically, the Vragenderveen dams were completed in January 2002, almost one year ahead of schedule. Two parallel dams were also built between the Nijenhuisdam and the Korenburgerveensloot. The Dal van de Schaarsbeek levee was constructed and the river successfully reshaped, allowing the digging of a parallel ditch to capture runoff water containing nitrates from surrounding farmland. Both the Pollendijk and Corlese Veen dams were built as planned. The impact of the project actions has been noticeable: the average groundwater level has increased and it decreases by less during the summer period than before the project. This was one of the main objectives of the restoration works. Improvements in water quality after the works are not clear and monitoring of water quality parameters should go on in order to intervene if necessary. Monitoring indicates an increase in numbers of mosses that are characteristic of raised bogs. However, the development of vegetation differs by area and it is not always clear in which direction it will evolve, as in several cases plant species that are indicative of different conditions have been found together in the same area. In the central part of the Vragenderveen, the signs appear to be positive with an increased distribution of raised bog species. However, in other areas this effect is not apparent, with an increase in species that favour more alkaline conditions. Attention should be paid to the threat of eutrophication and consequences for the flora and fauna in the area. Whether the ecological objectives of the project will be achieved is still to be seen over 25-30 years. In the next few years it will be possible to assess whether the site is developing as expected.