『Abstract
　A case study was carried out with the aim to practically test whether estimates of groundwater discharge rates into dredging lakes can be made via an uncomplicated and straightforward technique using radon-222 as naturally-occurring groundwater tracer. Lake Ammelshainer See, a dredging, seepage lake, approximately 25 km east of Leipzig, Germany, was chosen as the investigation site. In order to evaluate changes in the spatial and temporal radon-222 patterns in the lake during different stages of stratification, sampling campaigns were conducted in April 2007 (well mixed stage) and in May 2007 (thermal stratification stage). Groundwater flow estimates were made using a radon mass balance approach accounting for all radon fluxes into and out of the lake and assuming steady-state conditions with respect to these radon fluxes. Once all positive and negative radon fluxes related to the lake water volume were determined, groundwater discharge was estimated by using the advective radon input and the radon activity concentration of the porewater as key parameters. The results showed that in case of a lake with a size and shape of Lake Ammelshainer See (530,000 m²) reasonable groundwater discharge estimates can be made by collection and analyzing just a few water samples and a few samples from the sediment layer.

Keywords: Radiogenic isotopes; Groundwater; Surface water; Interaction; Lake; Germany』

Introduction
Study area
Materials and methods
　Modeling approach
　Sampling and measurement
　　On-site activities
　　Laboratory measurements
　Hydrologic studies based on Darcy's law
Results
　pH, electrical conductivity, and temperature depth profiles
　Excess radon-222 profiles
　Radon concentration of the discharging water
　Diffusive benthic fluxes
　Atmospheric evasion
　Radon budget and groundwater discharge
Summary and conclusion
Acknowledgments
References