During heavy rainfall, wastewater treatment plants (WWTPs) are often unable to cope with the volumes of water arising, and some wastewater may then be discharged untreated into surface waters. Eawag, in cooperation with the HSR (Hochschule für Technik Rapperswil) and industrial partners, has developed a control system which ensures more efficient use of the storage capacity of existing wastewater infrastructure. Software known as INKA processes measurement data from the sewer network, information on the condition of receiving waters and precipitation data so as to calculate the optimal outflow volumes. The system ensures more even utilization of WWTP capacity in wet weather and controlled retention of excess wastewater within the sewer network. As well as improving water pollution control, this makes it possible to operate sewer networks more cost-effectively.