Professor and Program Director Milwaukee School of Engineering
When modeling wet weather flow in sanitary sewers the RTK method is often used. The RTK method converts a specified amount of rainfall into sewer flow, regardless of changes in the soil’s moisture content and saturation. Robert Czachorski and Tobin VanPelt (2001) sought to remedy this issue when they developed the antecedent moisture modeling (AMM) procedure, which explicitly accounts for antecedent moisture conditions. AMM tracks antecedent moisture using rain and temperature signals. The rain signal adds moisture to the soil according to the magnitude of the temperature signal. High temperatures reduce added soil moisture because evaporation and transpiration are higher, resulting in drier antecedent moisture conditions, while low temperatures do the reverse. Since 2021, AMM has been applied with great success on hundreds of projects. AMM, in its current form as documented by Czachorski, Edgren and Gonwa (2022), has the potential to revolutionize sanitary sewer system modeling. Nearby streams experience roughly the same antecedent moisture conditions as a sanitary sewer system. Is it possible that streamflow provides a better indicator signal of antecedent moisture conditions than temperature? Preliminary testing shows promise. This presentation provides the results of a more complete exploration of streamflow as an indicator of antecedent moisture conditions in AMM, along with the utility of AMM to accurately simulate wet weather flow in sanitary sewers.
