Using Electrical Conductivity as a Proxy for Q: A Madman’s Delusion or Elusive Science

Salt Dilution (SD) is an accurate, safe, relatively inexpensive, and easily employed method to measure water flow in turbulent streams and rivers. Often, Temperature Compensated Electrical Conductivity (EC.T) sensors are deployed continuously in Automated Salt Dilution (AQ) flow measurement systems. Recent studies (Cano-Paoli, K., Chiogna, G., and Bellin, A. 2019) have examined how well a continuous EC.T record can be used in regression analysis to estimate the Discharge. EC.T has the benefit of not requiring a stable Pressure Transducer (PT) elevation and avoids other complications of a stage-discharge station, such as shifting hydraulic controls. However, EC.T can be impacted by sediment fouling, aeration, and seasonal/storm event-related changes to the relationship with Q. This study examines how robust a combined stage-discharge-EC.T time series can be for the generation of a maximum likelihood flow hydrograph. This relationship can be useful for infilling missing data and determining hydraulic control shifts in the stage-discharge relationship. Examples are presented from several mountainous catchments.