Building up competence in hydrogeology in Lusatia

Country / Region: Germany: Saxony and Brandenburg

Begin of project: July 15, 2022

End of project: June 30, 2024

Status of project: March 16, 2023

Lignite mining has considerably affected the water balance of the Lusatian river systems (Spree, Schwarze Elster and Lausitzer Neiße) and their adjacent aquifer systems. The mining related impacts will continue to place high demands on the region's water management beyond the scheduled mining phase out in the year 2038. In this context, mathematical models can assist to understand and to quantify the processes taking place in the hydrological system and support water management planning.
The KoHyLa project investigates how the hydrological and hydrogeological processes of Lusatia can be optimally represented in an overarching numerical model. Computational challenges arise, for example, from the requirement to jointly simulate the complex interactions between groundwater and surface waters in the catchments of the three main rivers of Lusatia. In addition, the anthropogenic influences on the natural hydrological conditions in Lusatia, for example through cut-off walls, residual lakes still being flooded, and the regional groundwater drawdown, must be integrated into the modeling system.

Another project focus is the representation of “complex subregions” - examples are the Muskauer Faltenbogen and the Spreewald – within the regional model. These areas should be considered simplified but nevertheless adequate within the upcoming model. For this purpose, models of these subregions are set up to test the impact of simplification strategies.

KoHyLa consists of several components. In the first component, data are collected, analyzed, and evaluated to develop an understanding of the geological subsurface of Lusatia in the form of a conceptual model. In the second step, a simplified groundwater flow model will be created to represent the groundwater budget, including complex interactions with surface waters. The model extent and resolution can be adjusted automatically as it is embedded in a Python-based framework.

The insights gained in the project on the hydrological and hydrogeological conditions of Lusatia will form the basis for future FEZB projects and for consulting services within the framework of the Lusatian groundwater model.

Project goals:

• To develop competence with regard to the hydrogeology and hydrology of Lusatia and its model-based simulation
• To adequately consider the interactions of groundwater and surface waters as well as anthropogenic influences in large-scale groundwater flow models
• To represent complex subregions, regarding their geology or water management, in a simplified way in large-scale groundwater flow models

Example calculation of the hydraulic potential of the near-surface aquifer in Lusatia with MODFLOW 6 Source: BGR