San Lorenzo River: What’s in a Watershed: Part I

A juvenile steelhead trout is counted as part of a fish count conducted by the City of Santa Cruz annually. .
A juvenile steelhead trout from Laguna Creek caught during the City’s summer lagoon surveys in 2013. Photo courtesy of and © Jeff Hagar.

If you live in a watershed, does that make you an aquatic creature? Of course not! A watershed is the geographic area that drains to a common surface or water body. It’s made up of not only the rivers, lakes, aquifers, creeks, and streams, but also the area of land surrounding these bodies of water.

A watershed is the area of land where all of the water drains to the same river, creek or stream. In this diagram, the watershed boundary is marked with the dotted purple line. Photo courtesy and © of the Central Sierra Environmental Resource Center.
A watershed is the area of land where all of the water drains to the same river, creek or stream. In this diagram, the watershed boundary is marked with the dotted purple line. Photo courtesy of and © Central Sierra Environmental Resource Center.

San Lorenzo River Watershed

Have you visited the towns of Santa Cruz, Felton, Ben Lomond, Brookdale or Boulder Creek? Have you spent time in Fall Creek State Park, Henry Cowell State Park, Pogonip Open Space, Quail Hollow Ranch Park or Castle Rock State Park? If so, you’ve visited the San Lorenzo River watershed. This is the largest watershed in Santa Cruz County, spanning 135 square miles. One of the best ways to go explore the entire watershed is to get in your car and travel up the winding roads of Highway 9, that is, if you don’t get car-sick.

See if you can trace the San Lorenzo River from the Boardwalk to the Santa Cruz Mountains and find out if you live in or are visiting the San Lorenzo Watershed. Map courtesy of Santa Cruz County Geographic Information Systems.
See if you can trace the San Lorenzo River from the Boardwalk to the Santa Cruz Mountains and find out if you live in or are visiting the San Lorenzo Watershed. Map courtesy of and © Santa Cruz County Geographic Information Systems.

Much of the watershed is comprised of the Santa Cruz Mountains, which are part of the Pacific Coast Range. These mountains are made of sedimentary rock which is slowly being uplifted. The watershed is very prone to erosion, which results in the high levels of sedimentation throughout the river and in downstream reaches that are the most important for salmonid habitat.

The San Lorenzo River watershed has varying discharge and rainfall depending on where you are. Rainfall can be less than 25 inches per year near the ocean, to up to 60 inches in the higher mountain elevations. Wherever it falls in the watershed, much of it drains to the sea. The hydrograph below shows the amount of water flowing into the sea at the mouth of the San Lorenzo between 2012 and 2014. The values range from only a few cubic feet per second in the summer to hundreds of cubic feet per second during winter storms. Particularly strong winter storms can result in discharge rates over 1000 cubic feet per second. Large storms also deposit lots of sediment into the river at once.

Hydrograph showing mean discharge of San Lorenzo River at Santa Cruz from January 2012 to January 2014, in cubic feet per second. Graph courtesy and © of USGS.
Hydrograph showing mean discharge of San Lorenzo River at Santa Cruz from January 2012 to January 2014, in cubic feet per second. Graph © of USGS.

We use the San Lorenzo River watershed for a variety of reasons, and we use it a lot. Rock and sand quarries, logging and human occupancy are the three major human uses. These activities all contribute to sediment build up in the water column, which negatively affects river health. Septic systems and livestock surrounding the river increase pathogen and nitrate levels. All of our actions within the watershed can affect this important river ecosystem.

The San Lorenzo River watershed contains not only the San Lorenzo River, but also the river’s tributaries including Boulder Creek, Zayante Creek, Carbonera Creek and Branciforte Creek.

Branciforte Creek: A Dam Removed

The lower portion of Branciforte Creek, like the San Lorenzo River, is contained within a system flood control structures. However, unlike the San Lorenzo, there’s not much vegetation and plant life within the concrete walls of the Branciforte Creek channel.

The channelized lower portion of Branciforte Creek meets the San Lorenzo River in downtown Santa Cruz. Photo courtesy and © of the Coastal Watershed Council.
The channelized lower portion of Branciforte Creek meets the San Lorenzo River in downtown Santa Cruz. Photo courtesy of and © Coastal Watershed Council.

From this confluence, Branciforte Creek travels up into the Happy Valley area of Santa Cruz along the road aptly named Branciforte Drive. You can visit the upper areas of Branciforte Creek by visiting Delaveaga Park and then taking a short hike to the riverbank.

In 2013, a dam was removed on Branciforte Creek. The dam, constructed in 1931, was no longer serving its initial purposes for water supply, recreation and fire protection. Its removal came after a push by local, state, and federal resource agencies to remove barriers to salmonid migration.

 Dam on Branciforte Creek before removal. Photo courtesy of Resource Conservation District of Santa Cruz County.
Dam on Branciforte Creek before removal. Photo courtesy of and © Resource Conservation District of Santa Cruz County.
Dam removal in progress on Branciforte Creek in 2013. Photo courtesy of Resource Conservation District of Santa Cruz County.
Dam removal in progress on Branciforte Creek in 2013. Photo courtesy of and © Resource Conservation District of Santa Cruz County.
Immediately after removal of dam on Branciforte Creek. Photo courtesy and © of Resource Conservation District of Santa Cruz County.
Immediately after removal of dam on Branciforte Creek. Photo courtesy of and © Resource Conservation District of Santa Cruz County.
Two years after the dam was removed, a healthy ecosystem thrives here on Branciforte Creek. Photo courtesy and copyright of Resource Conservation District of Santa Cruz County.
Two years after the dam was removed, a healthy ecosystem thrives here on Branciforte Creek. Photo courtesy of and © Resource Conservation District of Santa Cruz County.

The Resource Conservation District of Santa Cruz County brought down the dam, with partners like American Rivers, NOAA and the County of Santa Cruz. The dam was removed and wood structures, vegetation and erosion control measures were installed. This project opened almost three miles of upstream spawning and rearing habitat for salmonids and will hopefully encourage the removal of other fish passage barriers throughout Branciforte Creek and San Lorenzo River.

Take the Self-Guided Mobile Tour

This piece is part of the San Lorenzo River Tour by the Coastal Watershed Council. Download the free app with many tours of the Santa Cruz area and beyond.

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Go to Mobile Ranger Guides in the Apple App Store
Go to Mobile Ranger Guides in the Google Play Store
  1. Sources Used




About The Author

Coastal Watershed Council

The Coastal Watershed Council is a nonprofit organization formed in 1995 in response to the declining health of watersheds in the Monterey Bay region. Our mission is to preserve and protect coastal watersheds through community stewardship, education and monitoring.

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