Groundwater flow modeling in a karst area, Blau Valley, Germany

Abstract

Karst aquifers typically have complex flow patterns as a result of the depositional heterogeneities and large conduits from dissolution features. Various field measurements were carried out to build a hydrogeological conceptual model of the Jurassic aquifer close to Blaubeuren (Germany), including drilling data, well tests, and geophysical surveys. These data were assembled to simulate the groundwater flow at a site where a possible new pumped-storage plant is in planning approval. The favorable layout of the lower reservoir is designed without sealing to the connected karst aquifer underneath. Approving this construction concept, various measures and strategies have to be formulated by using numerical modeling to limit possible adverse impacts on the construction site and its environment, considering that the Blau Valley requires high level of protection. Based on the conceptual model, the aquifer system is represented by a three-dimensional finite element model using the FEFLOW numerical code. The model is calibrated for steady-state and transient conditions by matching computed and measured piezometric levels (November 2012—March 2013) from over 30 observation wells to estimate the best-fitted spatial distribution of both hydraulic conductivity and storage coefficient in the aquifer. The model is used to analyze quantitatively the flow regime, the groundwater mass balance, and the aquifer hydraulic properties of this karst area. The results of the study provide necessary information regarding the hydraulic behavior of the aquifer in order to plan the construction phase and the subsequent operation of the pumped-storage plant.