Within the framework of DFG research group CAOS, the goal of this project is to develop methods for optimal quantitative precipitation estimation (QPE) with high resolution in space and time. To this end we combine observations from C-band weather radar, Dual-Pol radar, Micro Rain radar, Distrometers and rain gauges. In addition, we merge observation-based QPE with results from numerical weather modeling through data assimilation. Test area is the 288 km2 Attert catchment in Luxembourg.