10.4122/1.1000001751 Kayhanian, M. Ha, S. Stenstrom, M. K. Constituents'' annual load estimation from highways DTU Library, Technical University of Denmark (DTU) 2005 Highway runoff GIS event mean concentration (EMC) rational method constituent load estimation stormwater University of California, Center for Environmental and Water Resources Engineering University of California, Department of Civil and Environmental Engineering en Conference presentation 10.4122/1.1000001752 text/xml 1 Constituents\342\200\231 Annual Loads Estimation (CALE) is a program to estimate annual stormwater runoff constituent loads from highways and their shoulders. It uses Visual Basic for Applications, which is included with ArcGIS Desktop (ESRI, Redlands, CA). The program is based on the rational method and Event Mean Concentrations (EMCs), which has become a popular method of estimating constituent loads. The program uses several data sources which are spatially referenced by incorporation into Geographical Information System (GIS) layers. The program is automated in that the user only needs to select specific watersheds. The watersheds are highlighted by the GIS application and the constituent loads are presented in tables. Results obtained by CALE showed that the improved area calculation and the use of regional EMC reduces the estimated load by up to 40% for most constituents over earlier, simpler models.