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Delta Watersheds

What is a watershed?
A watershed is a land that water flows through before it drains into a creek, a river or the sea. 

The picture to the left is the San Joaquin River and is part of a large watershed. 

The Marsh Creek is also a watershed.

Photo by the Delta Science Center

The Marsh Creek Watershed
The Marsh Creek Watershed drains the east side of Mount Diablo. It covers about 128 square miles of rangeland, farmland, protected parkland and urban land. 

Marsh Creek flows near an abandoned mercury mine, which is tainting the runoff of a Marsh Creek Tributary. This in turn not only contaminates the Delta, but also contaminates the Chinook salmon that swim in the ocean, the Delta and up Marsh Creek to spawn. 

For more information on the Marsh Creek Watershed see the Friends of Marsh Creek's website at

San Joaquin River Watershed
Another watershed within the Sacramento-San Joaquin Delta is the San Joaquin River Watershed. The San Joaquin River is about 300 miles long. It begins in the Sierra Nevada mountain range on California's eastern border. The river runs down the western slope of the Sierra and flows roughly northwest through the Central Valley, to where it meets the Sacramento River at the Sacramento-San Joaquin Delta. 

 Photo and map courtesy USGS.