Quantifying Nonstorm-Water Discharges to Storm-Water Systems with Model Analysis

Many separate storm-water systems in China suffer functional problems of discharge of dry-weather pollutants or non-storm-water materials into storm-water systems via pipes or other direct connections, which plays as a main contributor to receiving water pollution. The general methods of identifying and locating illicit connections are not really suitable for pump drainage systems with severe problems on the decision-making level. This note presents an efficient methodology for diagnosing the systems and quantifying the flow rate of non-storm-water inflow with a hydraulic model. In this methodology, complicated hydraulic connections were simplified to virtual equivalent pipes, and then hydraulic parameters of the equivalent pipes were calibrated and verified with the hydraulic model that was built based on fieldwork. The method was successfully applied to the North Beixinjing storm-water system along the Suzhou Creek, Shanghai, China to quantify dry-weather flow from illicit connections and inflow of receiving body into the storm-water systems.