Fig. 3

The hydrogeological map shows the basic hydrogeological characteristics of the study site (red). The aquifer in the northern part of the study area contains the Upper and Lower Aquifer, the one in the south consists only of the Upper Aquifer. The area with a restriction on the allowed drilling depth defined by the online information system for shallow geothermal energy for the state of Baden-Württemberg, called ISONG (LGRB 2017) is marked yellow, and the cross section used for the energy flow approach is indicated by the green line. The groundwater flow direction is north-westwards