The Arana Gulch Watershed, a 3.5-square-mile basin, is in the middle of Santa Cruz County, 25 miles south of San Mateo County and 25 miles north of Monterey County. The headwaters begin 600 feet above sea level in the foothills of the Santa Cruz Mountains. The upper portion of the watershed is rural and steep (up to 70 percent grade). Three tributaries converge at the beginning of the flood plain behind the Oak Meadow Cemetery. Arana Creek passes under Highway 1 and flows adjacent the Harbor High School athletic fields and through the Arana Gulch Greenbelt open space before draining into the Santa Cruz Small Craft Harbor and the Monterey Bay National Marine Sanctuary. The lower watershed is primarily within the Coastal Zone, while the upper reaches extend beyond it.
The Arana Gulch watershed is representative in size of many small coastal watersheds in central California. Small watersheds are often the breeding grounds of relic populations of steelhead, which raises the preservation stakes. To ensure their adaptability to changing environmental conditions, it is critical to maintain genetic diversity within the species.
There are several jurisdictions that have watershed management responsibilities in the Arana Gulch watershed, including the City and County of Santa Cruz. Additionally, the lower reaches of the watershed fall within the Coastal Zone, the Santa Cruz Port District, and the Monterey Bay National Marine Sanctuary.
Much of the lower mile of Arana Creek flows through a residential and mixed-use area. While facing some of the typical problems associated with urbanization, particularly relating to fish passage, the crucial lowermost and estuarine reaches of the stream are in public ownership with adequate buffers to provide fish and wildlife habitat. AGWA has made considerable strides in making this urbanized reach passable and usable, and plans to continue and expand this effort.
The upper reaches of the stream and its major tributaries flow through several miles of large parcels and extensive open-space holdings supporting grasslands, mixed woodlands, redwoods, and coastal scrub. Many of the factors affecting the lower reaches, particularly as they relate to steelhead restoration and sedimentation in the harbor, have their origins in the upper watershed. For example, due to a water diversion above the property and poor grading, Arana Creek eroded a gully 75 yards long and 8-10 feet deep through an orchard, resulting in the loss of trees and an increase in the sediment load. More native riparian woodland cover adjoining the stream is needed, both to stabilize eroding bank segments and to provide the corridor values and cover needed for a restored natural system.