The National Pollutant Discharge Elimination System MS4 Permit in the County of Los Angeles was issued in 2012. The Permit provided for Permittees to collaboratively develop an Enhanced Watershed Management Program (EWMP). The EWMP approach allows for Permittees to comprehensively implement watershed based collaboration among Permittees and other partners on multi-benefit projects that retain all non-storm water runoff and runoff from the 85th percentile, 24-hour storm event. The permittees developed a EWMP and Coordinated Integrated Monitoring Program for the Santa Clara River to comply with requirements in the Permit. The state is now drafting the next permit that includes regional, watershed based permit for compliance. The City of Santa Clarita is also a member of the Regional Water Management Group of the Upper Santa Clara River Integrated Regional Water Management Plan. Measure W, a countywide tax approved by the voters in 2018, is distributed on a watershed basis through watershed steering committees. Watershed approaches have their benefits, but also require a different set of compliance skills. This presentation will focus on the lessons learned watershed based compliance.