The SPAW Model: Application to Infiltrating BMP Facilities

The recently formulated SPAW model provides comprehensive soil moisture accounting in agricultural ecosystems. This paper examines how SPAW can be applied to infiltrating BMPs under the much higher runoff loading rates typical of urban runoff BMPS. Using SPAW, it is thus possible to better project the important BMP performance characteristics of interception percentage and retention time as a function of media infiltration properties. SPAW results can then be integrated with detention routing procedures to project runoff volume and peak flow reductions provided by distributed BMP facilities. A case study of biofiltration swales with check dams to provide detention storage is then presented. In over 5 km of biofiltration swales the effect of stone check dams placed every 30 to 35 meters to provide detention storage has been modeled for its effect upon infiltration volumes. This presentation summarizes the hydrological approach, and presents hydrographs that demonstrate the very promising potential of distributed infiltration BMPs.