Calibration and validation of a groundwater model in Switzerland. The Wasseramt aquifer.

In 2006, a 2D groundwater flow model was built and calibrated using hydraulic data in the period 2002-2005. Since 2006 many things have changed in the area. For instance, new pumping wells have been drilled, or the pumping rates at existing wells have been modified. This projects updates the existing model with the new topology and includes new data, e.g., heads at new wells or extension of the existing records, new hydraulic tests, etc.

A major modification to the existing model is the transient modelling of the two main rivers in the area, i.e., Emme and Aare. The water table there is included in the model as prescribed (transient) head boundary conditions. One of the main novelties in this work is the use of an enhanced version of the software Spring. The previous model was calibrated using version 3.4, whereas the new model is calibrated using version 4.1, which amongst other enhancements, greatly improves the treatment of boundary conditions like leakage at water courses. Spring 4.1 is coupled with PEST (Parameter ESTimation software; Watermark Numerical Computing, 2010). PEST undertakes the automatic calibration of model parameters (hydraulic conductivity and leakage coefficient at water courses in this work) via the pilot points method incorporating prior information of model parameters.