Pollutant Load Estimation for Water Quality Monitoring Projects

Abstract

monitoring projects. The mass of nutrients delivered to a lake or estuary drives the productivity of the waterbody. The annual suspended sediment load transported by a river is usually a more meaningful indicator of soil loss in the watershed than is a suspended sediment concentration. The foundation of water resource management embodied in the TMDL (total maximum daily load) concept lies in assessment of the maximum pollutant load a waterbody can accept before becoming impaired and in the measurement of changes in pollutant loads in response to implementation of management measures. Estimation of pollutant load through monitoring is a complex task that requires accurate measurement of both pollutant concentration and water flow and careful calculation, often based on a statistical approach. It is imperative that a NPS monitoring program be designed for good load estimation at the start. This Tech Note addresses important considerations and procedures for developing good pollutant load estimates in NPS monitoring projects. Much of the material is taken from an extensive monograph written by Dr. R. Peter Richards, of Heidelberg University, Estimation of Pollutant Loads in Rivers and Streams: A Guidance Document for NPS Programs. The reader is encouraged to consult that document and its associated tools for additional information on load estimation.