Mapping and Quantification of groundwater inflow into lake Ammersee, upper Bavaria

Silvia Schultes1, Catharina Keim, Benjamin Gilfedder
1 Limnologische Station, Universität Bayreuth

P 4.8 in BayCEERversity: Across scales, compartments & communities

Introduction

From previous investigations (Bueche & Vetter 2014) is known, that lake Ammersee is recharged by groundwater to a certain percentage. Groundwater inflow spots are mapped by the groundwater indicator Radon (222Rn) and inflowing groundwater will be quantified.

Material and Methods

The first investigation was conducted in April 2017 on the southern shore of lake Ammersee. The Radon concentration in around 1,5 m water depth along the southern shore was mapped by a continuous method of Radon measurement. Seefloor close water samples were taken along the same track for the analysing of Radon and further chemical parameters (point measurements).

Results

First examination of point measurements reveal Radon concentrations up to 100 Bq/m3 in the southeastern area and around the estuary of the river Ammer (see figure 1). The continuous measurements show Radon concentrations between 26 Bq/m3 and 96 Bq/m3.

In July 2017 a second field campaign was conducted. Areas with high Radon concentrations measured in the first campaign were studied in detail. One spot at the eastern shore of lake Ammersee shows maximum concentrations in the second investigation up the 72 Bq/m³ (see figure 2). Radon concentrations of water samples in the eastern bay of lake Ammersee (Herrschinger Bucht) are up to 101 Bq/ m³ (see figure 2).

Conclusions

Results of both field campaigns indicate an important groundwater inflow in the southeast area of lake Ammersee. Especially one spot on the eastern shore analysed in the second field campaign confirms groundwater inflow because of maximum Radon concentrations in that area. Furthermore, results of the second field campaign reveal important groundwater inflow in th north of the bay in the eastern part of lake Ammersee (Herrschinger Bucht).
All Radon measurements as well as the installed seepage meters in the northern area of the bay of lake Ammersee (Herrschinger Bucht) will provide information about the quantity of groundwater inflow.