Mapping and quantifying groundwater inflow to the Spree River (Lusatia) and its role in Fe precipitation and coating of the river bed

摘要

Local groundwater inflow is an unknown but central component for the precipitation and accumulation of iron in the Spree River, Lusatia. In this study, the natural tracer radon was used to map and quantify local groundwater inflows into the Spree and Kleine Spree rivers in the Lusatian lignite mining district. During two measurement campaigns, the total groundwater inflow for a 20 km long reach of the Kleine Spree and a 34 km long reach of the Spree ranged between similar to 3,000 and similar to 7,000 m(3)d(-1) (Kleine Spree) and between similar to 20,000 and similar to 38,000m(3)d(-1) (Spree). Particularly high groundwater inflow was identified (up to 70% of total inflow) along the Spreewitzer Rinne, a local aquifer consisting of excavated mining materials. Along these river reaches, large amounts of dissolved iron are entering the rivers with inflowing groundwater. Using the measured iron and sulphate loadings, we calculated that up to 120 tons/day of iron (oxy)-hydroxide was retained in the combined Spree and Klein Spree catchments.