San Diego County is located in the far southwestern corner of the state of California in the United States of America. The County has incrediable biodiversity and contains 99 threatened or endangered species, the higest number of any County in the United States.

What is a Watershed? Definition: The specific land area that drains water into a river system or other body of water. Watersheds are also sometimes referred to as drainage basins or drainage areas with the technical term being hydrologic units. Ridges of higher ground generally form the boundaries between watersheds. At these boundaries, rain falling on one side flows toward the low point of one watershed, while rain falling on the other side of the boundary flows toward the low point of a different watershed.

The United States is divided into 18 major drainage areas and 160 principal river drainage basins containing about 12,700 smaller watersheds. California has 153 watersheds. San Diego County contains 16 watersheds with 11 major hydrologic units draining into the Pacific Ocean or San Diego Bay. The Project Clean Water website at Project Clean Water has very good detailed information on our watersheds.
The San Diego Stream Team historically has conducted bioassessment in nine of our watersheds and currently focuses on the following:
Carlsbad
Los Penasquitos
San Diego
San Luis Rey
Tijuana