The hydrogeology of a catchment area and an artificially divided dystrophic lake - consequences for the limnology of Lake Fuchskuhle

The hydrogeology between the catchment area and the divided dystrophic Lake Fuchskuhle with respect to the genesis and the land-water interactions were investigated. Water levels at numerous locations in the catchment area were measured in order to characterize the hydrology. The water balance of the area was calculated based on long term climatic investigations. The geology of the peat was documented at 25 sampling points by cores collected with a peat drill. Chemical parameters including pH. total phosphorus and total nitrogen concentrations. DOC concentration. colour (SAK 436 m(-1)) and the UV254/DOC ratio in the catchment area and in two compartments (NE and SW compartment) were determined, The chemical fluxes of DOC, nitrogen and phosphorus from the catchment area into one compartment (SW compartment) were deter-mined. During the genesis of the Lake Fuchskuhle area two aquifer systems (local peat aquifer, regional sandy main aquifer) developed. Both aquifers are largely independently with almost no lateral interactions. Two compartments are supplied with water from the local peat aquifer. From the other two compartments, however. water is flowing out into the peat body. During high groundwater inflow into the SW compartment higher concentration of DOC. nitrogen and phosphorus in the SW compartment were detected. The fen can be divided in two parts: in the meso - to eutrophic fen northwest and the mainly meso - to oligotrophic - acid fen in the southeast. The significant differences in parameters such as pH. conductivity and DOC concentration gave a clear picture of the heterogeneity of the two compartments and their dependence on the catchment area with the two aquifers.