A current guideline document of the German Federal state of Hesse on the analysis of impacts of wastewater discharges on river water quality was extended by dynamical modelling approaches. At the Technical University of Darmstadt, a methodology, based on the pollutant load model SMUSI 5.0, was developed. ifak developed a river water quality model suitable for practical applications (‘Simple Water Quality Model’). The connection to a framework with OpenMI interface allows integration also of third-party component packages.