Canal blocking strategies for hydrological restoration of degraded tropical peatlands in Central Kalimantan, Indonesia

In the 1990s the Government of Indonesia decided to develop one million hectares of peatlands for agriculture in Central Kalimantan on the Island of Borneo. The construction of thousands of kilometres of canals resulted in over-drainage and targets for agricultural production failed. Abandoned, the area has been subject to severe forest and peat fires. Restoration of degraded peatlands normally starts with restoring the water table to rewet the surface in order to control fire and to initiate reforestation. Canal blocking strategies are a potential means for accomplishing this. In a test plot in the Northern part of Block C of the former Mega Rice Project (MRP), a series of dams were constructed and (ground)water tables and subsidence rates were monitored to assess the effects of dam construction on peatland hydrology. The resulting higher water tables did not completely compensate for the negative effects of increased subsidence near the canals. The canals, which are “eating” themselves into the peatland, create depressions in the peatland surface leading to interception of overland- and interflow and increased risk of overtopping of dams during extreme rainfall events. The lessons learned are being used to improve blocking strategies and dam design. The changes in peatland topography caused by drainage, however, need to be better understood in order to further refine strategies for hydrological restoration of degraded peatlands in Indonesia.