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.

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.

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.

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.

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.

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.