Select a language:

Rain & Stream Data

OC Watersheds is responsible for a wide array of programs designed to assess the status of the surface water environment in Orange County. The North and South OC Monitoring and Assessment Sections manage environmental monitoring, and Geographical Information System (GIS) data and provide Orange County rainfall information for the latest as well as historic storm events. These Sections install operate a network of rainfall and stream gage stations located throughout Orange County, which comprise the Automated Local Evaluation in Real Time (ALERT) system.

Please visit the OC Environmental Resources GIS/Data Portal (below left) for access to a number of interactive maps and GIS data, and the Hydrology Data Portal (below right) for access to current and historic rainfall and stream gage data:

OC GIS PORTAL Hydro Data Portal

The Monitoring and Assessment Sections are also responsible for implementing environmental monitoring programs required by the area wide municipal stormwater permits issued to the County and cities of Orange County by the Santa Ana and San Diego Regional Water Boards, otherwise known as "municipal separate storm sewer system" or "MS4" permits. This unit also supports monitoring required by Total Maximum Daily Loads (TMDLs), the development and implementation of special monitoring studies, and participation in regional monitoring efforts such as the Stormwater Monitoring Coalition (SMC) and the Southern California Bight program.