Based on the Water Protection Act of 2013, severe issues caused by the rapid change of water discharge (hydropeaking) must be reduced by operators of hydroelectric power plants in Switzerland. Therefore, a new generation of regulating basins is under construction. In Tesin, the Ritom hydroelectric power plant, constructed in 1921, will be modernized. The project includes a new powerhouse with three machine groups. A compensation basin with a volume of 100’000 m3 is planned in order to minimize the effects of hydropeaking. The discharge exiting the basin to the Ticino will be controlled by a regulating structure. Due to the new compensation basin, the route of the Foss river needs to be modified and new weirs have to be installed to prevent the overflow of the Foss river into the compensation basin. Figure 1 shows the planned basin and the physical model boundaries.