The overall objective of the MuDak-WRM project is the development and application of a globally applicable management system for reservoirs and their basins. To succeed in this development, two major sub-goals have to be fulfilled. We will develop a methodology for a minimum monitoring to assess water quality. Additionally, the complexity of existing models needs to be reduced, to address globally restricted data and budget availability. The project includes monitoring of catchment and in-lake processes. Two case study sites were selected beforehand, the Große Dhünn reservoir in Germany and the Passauna reservoir in south-east Brazil. The monitoring results used for model parametrization lead to an improved system understanding, which again is the basis to define crucial monitoring parameters in space and time. With this information the efforts for an effective water quality observation will be reduced. A continuous assessment of the mass flux into the reservoir, water quality changes inside the reservoir as well as seasonal land cover changes have been successfully monitored in high resolution for an entire year. At the same time a water balance model has been set up in close relation to a catchment emission model.