Benny Selle

Catchments as reactors: a comprehensive approach for water fluxes and solute turnover

Sustainable water quality management requires a profound understanding of water fluxes (precipitation, run-off, recharge, etc.) and solute turnover such as retention, reaction, transformation, etc. at the catchment or landscape scale. The Water and Earth System Science competence cluster (WESS, http://www.wess.info/) aims at a holistic analysis of the water cycle coupled to reactive solute transport, including soil–plant–atmosphere and groundwater–surface water interactions. To facilitate exploring the impact of land-use and climate changes on water cycling and water quality, special emphasis is placed on feedbacks between the atmosphere, the land surface, and the subsurface. A major challenge lies in bridging the scales in monitoring and modeling of surface/subsurface versus atmospheric processes. The field work follows the approach of contrasting catchments, i.e. neighboring watersheds with different land use or similar watersheds with different climate. This paper introduces the featured catchments and explains methodologies of WESS by selected examples.

A data exploration framework for validation and setup of hydrological models

Over the course of hydrological research projects often a large number of heterogeneous data sets are acquired from sources as diverse as boreholes, gauging stations or satellite imagery. This data then need to be integrated into models for the simulation of hydrological processes. We propose a framework for exploration of geoscientific data and visually guided preparation of such models. Data sets from a large number of sources can be imported, combined and validated to avoid potential problems due to artefacts or inconsistencies between data sets in a subsequent simulation. Boundary conditions and domain discretisations for surface and subsurface models can be created and tested regarding criteria indicating possible numerical instabilities. All data sets including simulation results can be integrated into a user-controlled 3D scene and aspects of the data can be enhanced using a number of established visualisation techniques including thresholding and user-defined transfer functions. We present the application of this framework for the preparation of a model for simulation of groundwater flow in a river catchment in southwest Germany investigated in the scope of the WESS project.

Integrating hydrogeochemical, hydrogeological, and environmental tracer data to understand groundwater flow for a karstified aquifer system.

For karstified aquifer systems, numerical models of groundwater flow are difficult to setup and parameterize. However, a system understanding useful for groundwater management may be obtained without applying overly complicated models. In this study, we demonstrate for a karstified carbonate aquifer in south-western Germany that a combination of methods with moderate data requirements can be used to infer flowpaths and transit times of groundwater to production wells.

Case Study: Ammer Catchment

This chapter explains the step by step development of a steady state groundwater flow model with the help of the geographical information system ArcGIS and the numerical modelling tool OpenGeoSys. This groundwater flow model of a catchment in southwestern Germany was developed in the context of the Water Earth System Science (WESS) competence cluster. Details on the project may be found in an article by Grathwohl et al. (2013) or at www.wess.info. This case study focusses on the identification of flow paths and travel times of groundwater with respect to a number of production well sites. To this end, the best possible representation of the groundwater flow system was implemented as an OpenGeoSys simulation model. For more details on the development of a conceptual model of groundwater flow for the study area and the practical context of this work the interested reader is referred to articles by Pavlovskiy and Selle (2014) and Selle et al. (2013a).