Diverse Sediment Permeability and Implications for Groundwater Exchange in Closed Lake-Wetland Catchments (West Polesie, East Poland)

Abstract

Seepage lakes lacking surface-water inflow or outflow, but with surrounding peatlands, are important and vulnerable ecosystems with water budgets that depend largely on inputs from precipitation and groundwater discharge. We studied the sediment diversity in two such lake-wetland systems and their surrounding catchments. The lakes were located in relatively close proximity to one another within the West Polesie Transboundary Biosphere Reserve, West Polesie, East Poland. In spite of physiographic similarities, the studied lake-wetland systems and their catchments displayed considerable diversity in their underlying sediments. This was determined from data collected from several hundred geological boreholes and 164 determinations of the saturated hydraulic conductivity of the organic and mineral sediments (constant and falling head methods). Our research results showed that the functioning of a closed lake-wetland ecosystem is greatly influenced by the hydrogeological properties of its sediments. In the case of wetland zones surrounding lakes, especially closed-drainage seepage lakes, it is very important to identify the geological settings and the hydrogeological properties of those sediments in order to better understand groundwater influences.