Surface Water Monitoring
The Pajaro Valley Water Management Agency conducts monthly surface water quality checks at the monitoring sites shown on this map. Data collected helps the agency’s hydrologists in their work to maintain water quality throughout the basin.
There are three main watersheds located inside the Agency boundaries, which are the Corralitos Creek Watershed, the Carneros Creek Watershed, and the Watsonville/Harkins Slough Complex. The Pajaro River Watershed extends east of the Agency into San Benito County and is 1,200 square miles in size. The area contributing to the flow in the Pajaro River is much larger than all of the local watersheds combined. PVWMA monitors the surface water in the watersheds for electrical conductivity, calcium concentration, magnesium concentration, sodium concentration, chloride concentration, carbonate and bi-carbonate concentration, sulfate concentration, boron concentration, nitrate concentration, iron concentration, manganese concentration, potassium concentration, turbidity, and in select locations pesticides and fertilizers.
Corralitos Creek Watershed
The Corralitos watershed is the largest single watershed located within the Agency boundaries. The watershed includes Corralitos Creek, West Branch Corralitos Creek, Rider Creek, Browns Creek, Green Valley Creek, College Lake, Salsipuedes Creek, Hughes Creek, and Casserly Creek. All of the flow in this watershed empties into the Pajaro River near Watsonville. The average flow through Corralitos Creek measured at Green Valley Road is 11,350 acre-feet (AF).
Watsonville and Harkins Slough Complex
A network of sloughs drains the northwestern portions of the Pajaro basin. These sloughs include Harkins Slough, Hansens Slough, Galligans Slough, West Branch Slough, Struve Slough, and Watsonville Slough. All these sloughs drain into Watsonville Slough before it discharges into the mouth of the Pajaro River at Pajaro Dunes. The average annual flux through the entire slough system is 5,000 AF (Source: AMBAG, 1984)
Carneros Creek Watershed
This creek contributes the largest influx of freshwater into Elkhorn Slough, an average of 2,800 AF annually. Because this creek previously contained the flow of the Pajaro river, the substrate in the creek bed is very coarse sand. The coarse sand allows for a larger ratio of infiltration to flow in this channel than in any other waterway in the basin. Carneros Creek was dry from June until December during the 2000 water year. Because the flow in the creek drops to zero over the summer months, seawater from Elkhorn Slough can flow back into the creek bed during high tides. This causes vertical infiltration of seawater into the shallow aquifer along the creek-slough interface. Vertical seawater intrusion has been estimated at 2,000 - 4,000 AF per year and is a contributor to high chloride concentrations seen in wells located along Elkhorn Slough. (Source: Fugro West, 1995)