Integrated RWQM1 based water quality modelling using OpenMI, a case study of the river Zenne, Belgium

In the past, the QUAL principles have been widely used to describe the processes that define the oxygen levels in rivers. The more recently developed IWA river water quality model No.1 (RWQM1) has however a more sound theoretical background. Moreover, as the state variables of RWQM1 are similar to those of the activated sludge model for waste water treatment plants, RWQM1 better suits the needs in the framework of integrated river basin management. Accordingly, we used the RW QM1 principles to model the in-stream physico-chemical processes that affect the oxygen concentration. Hereby, the RWQM1 simulator was used as a model component in an integrated model that also contains three other models: a Soil and Water Assessment Tool (SWAT) model to simulate the hydrologic processes, the Storm Water Management Model (SW MM) to simulate the hydraulic processes and a stream water temperature model. We linked the models dynamically, using the Open Modelling Interface (OpenMI). The integrated model is applied to simulate the water quality of the river Zenne (Belgium). The results show that the integrated model simulates various components with a quality that ranges from 'Unsatisfactory' to 'Very Good'.