The impact of water management upon groundwater fluctuations in a disturbed bog relict

Abstract

In many disturbed bog relicts in northwestern Europe, attempts have been made to restore the hydrological conditions required for the reestablishment of ombrotrophic plant communities. Water management measures were taken to reduce water losses and to raise (ground) water levels in the bog relicts. Experiences show that after having taken these measures, on many sites groundwater levels remain low at the end of the summer. Suitable conditions for the regeneration of a Spagnum vegetation mostly are restricted to permanently inundated sites. The study presented here aims to clarify the importance of different hydrological characteristics such as hydro-physical properties of the peat layers, transpiration, downward water losses, etc. for the water fluctuations in bog relicts. A groundwater simulation model for peaty soils was developed (SWAMP, Soil Water Modelling in Peat), which makes it possible to evaluate alternative water management measures. In this study the model was used for a location in the Deurnese Peel area in the Netherlands. The results of this study demonstrate the importance of the hydro-physical characteristics of the peat layers for the pattern of groundwater fluctuations. More than any other hydrological variable it seems to be the pore size distribution within the upper peat layers that determines groundwater fluctuations. Probably in most disturbed bog relicts, the hydro-physical properties of the upper layers are not suited for the establishment of a Spagnum vegetation directly on the substrate. Only on permanently inundated sites floating mats of Spagnum peat can develop. On these sites gradually the required hydro-physical conditions within the young upper peat layers are created.