HYDROLOGICAL DIFFERENCES BETWEEN BOGS AND BOG-RELICTS AND CONSEQUENCES FOR BOG RESTORATION

The hydrology of bog relicts differs from that in undisturbed bogs. The surface layers of these relicts mostly consist of moderately to strongly humified, secondary weathered peat as a result of drainage and peat cutting. The hydrophysical properties of these layers cause relatively high groundwater level fluctuations. Deep drainage systems, both in the bog relicts and in their surroundings, may have increased the downward seepage. Reduction of these downward water losses may be crucial for the restoration of the required hydrological conditions in certain bog relicts (hydrological bufferzone as external water management option). The potential of internal hydrological modifications, where the increase in storage capacity near the surface is essential, should be emphasized in many bog relicts. Considerable reductions in water level fluctuations can be achieved e.g. when the open water within the area is enlarged and when this water is equally distributed over the area with small peat ridges in between. In general, attention should be given to both the internal and external options in studies on water man agement.