Physiographic and Climatic Controls on Regional Groundwater Dynamics.

The main goal of this study is to explore whether the ideas established by surface water hydrologists in the context of predictions in ungauged basins can be useful in hydrogeology. The concrete question is whether it is possible to create predictive models for groundwater systems with no or few observations based on knowledge derived from similar groundwater systems which are well observed. To do so, this study analyzes the relationship between temporal dynamics of groundwater levels and climatic and physiographic characteristics. The analysis is based on data from 341 wells in Southern Germany with 10‐year daily groundwater hydrographs. Observation wells are used in confined and unconfined sand and gravel aquifers from narrow mountainous valleys as well as more extensive lowland alluvial aquifers. Groundwater dynamics at each location are summarized with 46 indices describing features of groundwater hydrographs. Besides borehole log‐derived geologic information, local and regional morphologic characteristics as well as topography‐derived boundary and climatic descriptors were derived for each well. Regression relationships were established by mining the data for associations between dynamics and descriptors with forward stepwise regression at a confidence level >95%. The most important predictors are geology and boundary conditions and, secondarily, climate, as well as some topographic features, such as regional convergence. The multiple regression models are in general agreement with process understanding linked to groundwater dynamics in unconfined aquifers. This systematic investigation suggests that statistical regionalization of groundwater dynamics in ungauged aquifers based on map‐derived physiographic and climatic controls may be feasible. Key Points: Important physiographic and climatic controls on groundwater dynamics in Southern Germany are quantifiedEmpirical models are successfully constructed to explain groundwater dynamics based on climatic and physiographic system characteristicsThe constructed empirical models are generally consistent with physical process understanding [ABSTRACT FROM AUTHOR]