Pajaro River - Watershed

Watershed

The watershed is approximately 1,300 square miles (3,400 km2) and covers portions of Santa Cruz, Santa Clara, San Benito, and Monterey Counties. The Pajaro River mainstem begins just west of San Felipe Lake, also called Upper Soap Lake, which is a permanent natural lake formed by the confluence of Pacheco Creek, Tequisquita Slough and Ortega Creek. Pacheco Creek's headwaters are in the Diablo Range at about 400 feet (120 m) elevation. The Pajaro River mainstem flows west for 30 miles (50 km), passing the city of Watsonville and emptying into Monterey Bay. Lower Soap Lake, also called Soap Lake, is an intermittent body of water a few miles downstream of the upper lake. This type of water body forms when the channel below is unable to keep up with the flow coming from upstream.

San Felipe Lake lies just south of the Santa Clara County line in San Benito County, just south of Highway 152 east of Gilroy at the foot of the Diable Range. The lake is a sag pond dammed by the fault scarp of the Calaveras Fault, which forms a natural dike along the western shoreline. It is perennial in all but the driest years, e.g. 1977. San Felipe Lake used to be 50% larger until the man-made North and South Outflow canals, which drain to the Miller Canal, were cut through the western rim in 1874.

The Pajaro River's largest tributary is the San Benito River which is much longer than the Pajaro, flowing northwest from its source at an elevation of 4760 feet on San Benito Mountain on its course between the Diablo Range and the Gabilan Range, traveling for about 65 miles (105 km) before its confluence with the Pajaro River, about 15 miles (24 km) upstream from the ocean.

A residential development, agricultural fields, and Zmudowski State Beach border the Pajaro River mouth and the connecting Watsonville Slough. The river mouth is often open to tidal action for extended periods, especially during the winter months. Should the mouth fill with sediment, it must be physically reopened to prevent nearby agricultural fields from flooding.