The Trinity River Basin is part of the Klamath River Watershed. The Trinity River Basin encompasses approximately 2,900 square miles.
The Trinity is the longest tributary to the Klamath running approximately 130 miles from its headwaters in the Shasta Trinity National Forest (east of the Scott Mountains) to its confluence with the Klamath near Weitchpec in Humboldt County.
The Trinity is home to coho and Chinook salmon and steelhead trout. The Trinity River Diversion (part of the federal Central Valley Project), completed in 1963, diverts most of the flow from Trinity River into the Sacramento River.
In 1984, the Trinity River Restoration Program was initiated and a series of legislative decisions have resulted in increased flows to the Trinity, as well as significant restoration projects in the watershed.