Abstract: A system for controlling discharges of untreated water from a Combined Sewer System carrying rainwater and sewage from a drainage basin and having a Combined Sewage Overflow for discharging untreated material comprises the following: at least one cistern located within the drainage basin served by the Combined Sewer System, the cistern being positioned to capture rainwater that is collected from a portion of the drainage basin, the cistern having a drainage outlet for discharging water into the Combined Sewer System, the drainage outlet having a control valve positioned to control water flow through the drainage outlet, and the cistern also having an overflow outlet configured to discharge rainwater in the event that the cistern contains an amount of water approaching its capacity; a detector for obtaining data that correlates with water being discharged through the Combined Sewage Overflow; and a transmitter for remotely controlling the control valve.