@misc{HerrmannJahnkeJennetal., author = {Herrmann, Frank and Jahnke, Christoph and Jenn, Florian and Kunkel, Ralf and Voigt, Hans-J{\"u}rgen and Voigt, Jens and Wendland, Frank}, title = {Groundwater recharge rates for regional groundwater modelling: a case study using GROWA in the Lower Rhine lignite mining area, Germany}, abstract = {Abstract: Groundwater recharge rates calculated with the GROWA model have been applied as the recharge boundary condition for the regional groundwater model Rurscholle. This model simulates groundwater dynamics in the Pleistocene aquifers of the Lower Rhine lignite mining area (Germany). GROWA uses an area-differentiated approach to calculate recharge rates depending on runoff-relevant site characteristics, which are represented by a set of baseflow indices. The regional accuracy of the coupled groundwater and GROWA models has been checked using groundwater hydrographs as validation criteria. The results suggest that the current (unadjusted) version of GROWA underestimates the regional groundwater recharge rate by 10-20 mm/yr. The comparative analysis identified areas where recharge calculations could be improved by adjusting the baseflow indices for areas where runoff is dominated by slope, low water-logging and a low degree of sealing. Using the adjusted set of baseflow indices, the mean groundwater recharge rate of the Rurscholle region was modelled as approx. 170 mm/yr. This study highlights the benefit of using a coupled approach and being able to independently calibrate and validate groundwater recharge boundary conditions in regional groundwater models.}, language = {en} } @misc{WendlandBertholdFritscheetal., author = {Wendland, Frank and Berthold, Georg and Fritsche, Johann-Gerhard and Herrmann, Frank and Kunkel, Ralf and Voigt, Hans-J{\"u}rgen and Vereecken, Harry}, title = {A conceptual hydrogeological model for evaluating residence times in Hessen}, language = {en} } @article{KunkelWendlandHannappeletal., author = {Kunkel, Ralf and Wendland, Frank and Hannappel, Stephan and Voigt, Hans-J{\"u}rgen and Wolter, R.}, title = {The influence of diffuse pollution on groundwater content patterns for the groundwater bodies of Germany}, series = {Water Science and Technology}, volume = {55}, journal = {Water Science and Technology}, number = {3}, issn = {0273-1223}, pages = {97 -- 105}, abstract = {Commissioned by Germany's Working Group of the Federal States on Water Problems (LAWA) the authors developed a procedure to define natural groundwater conditions from groundwater monitoring data. The distribution pattern of a specific groundwater parameter observed by a number of groundwater monitoring stations within a petrographically comparable groundwater typology is reproduced by two statistical distribution functions, representing the "natural" and "influenced" component. The range of natural groundwater concentrations is characterized by confidence intervals of the distribution function of the natural component. The applicability of the approach was established for 17 hydrochemical different groundwater typologies occurring throughout Germany. Based on groundwater monitoring data from ca. 26,000 groundwater-monitoring stations, 40 different hydrochemical parameters were evaluated for each groundwater typology. For all investigated parameters the range of natural groundwater concentrations has been identified. According to the requirements of the EC Water Framework Directive (article 17) (WFD) this study is a basis for the German position to propose criteria for assessing a reference state for a "good groundwater chemical status".}, language = {en} }