Deriving Flows in a Waste Water System from SCADA Data

Traditional extensive monitoring campaigns ensure collection of flow data but tend to be expensive and can be unreliable. Tauranga City Council and DHI have worked together on a novel methodology for deriving flow information from water levels recorded at waste water pump stations. This methodology produces consistent, comprehensive records at a reasonable cost in a short time. 

Most urban utilities today collect large amounts of real time data that is captured by sensors and transmitted over a telemetry network. This data informs real time decisions in network operation, including alarm monitoring and emergency response to incidents and failures, yet these same utilities are often short of reliable flow data for model calibration and desktop analyses ( I&I assessment or pump station performance analysis in particular). 

Many SCADA systems have a built-in flow calculation routine, but often with severe limitations (e.g. unreliable in wet weather event or submerged inflows). The DHI flow derivation methodology overcomes these limitations by combining the information collected by SCADA with the network asset data, pump capacity curves, operational data and basic flow hydraulics. The methodology was verified against historical flow metering campaigns. Each derivation case was also “calibrated” against SCADA derived flows where these flows are known to be reliable. 

The process allowed TCC to extract a comprehensive historical record of inflows into the pump stations. This has proven beneficial and cost effective to all involved in the waste water system operations, maintenance and planning.