CNRFC - Hydrology - Observed River/Reservoir Conditions

SAN JOAQUIN RIVER - VERNALIS (VNSC1)

Latitude: 37.68º N	Longitude: 121.27º W	Elevation: 35 Feet
Location: San Joaquin County in California		River Group: San Joaquin

Monitor Stage: 24.5 Feet

Flood Stage: 29.0 Feet

Danger Stage: 29.5 Feet

Observed Data Credit
	Raw streamflow data is provided by the US Geological Survey (USGS). View USGS Data for this station location.

Historical Stage/Flow Data
Note: Water Year 2025 is currently showing peak daily mean values. These will be updated to instantaneous peaks in the coming months.
Water Year	Peak Discharge (cfs)	Stage (feet)	Date
Most Recent 5 Years
2025*	4,9400	12.97	Mar 20, 2025
2024*	10,300	18.12	Mar 6, 2024
2023*	34,400	29.82	Mar 19, 2023
2022*	2,600	10.83	Dec 29, 2021
2021*	2,470	10.76	Jan 31, 2021
Historical High Stage/Flow Events (Period of Record - Jul 1922 to Present) - Ranked by Flow
1951*	79,000	27.75	Dec 09, 1950
1997*	75,600	34.88	Jan 05, 1997
1969*	52,600	34.55	Jan 27, 1969
1938*	51,200	26.64	Mar 16, 1938
1956*	50,900	26.89	Dec 25, 1955
1983*	45,100	31.49	Mar 07, 1983
* Discharge affected by regulation or diversion

Location Photographs
Upstream Photo	Gage House Photo	Downstream Photo

ESRI™ Locator Map

Official 7 Day National Weather Service Forecast (CAZ019)

Tonight: Mostly cloudy. A slight chance of rain after midnight. Lows 44 to 51. Southeast winds up to 10 mph.

Sunday: Partly cloudy with a slight chance of rain in the morning, then mostly cloudy with a chance of rain in the afternoon. Highs 57 to 64. Southeast winds 10 to 15 mph with gusts to around 30 mph.

Sunday Night: Rain. Lows 45 to 50. Southeast winds 10 to 15 mph with gusts to around 25 mph.

washingtons birthday: Rain. Highs around 51. Southeast winds 10 to 15 mph. Gusts up to 25 mph in the afternoon.

Monday Night: Rain. Lows 39 to 44. South winds 10 to 15 mph with gusts to around 25 mph.

Tuesday: Rain. Highs 45 to 51.

Tuesday Night: Rain. Lows around 39.

Wednesday through Thursday: Mostly cloudy with a chance of rain. Highs 47 to 53. Lows around 38.

Thursday Night: Mostly cloudy with a slight chance of rain. Lows 33 to 39.

Friday through Saturday: Mostly cloudy with a chance of rain. Highs 52 to 57. Lows 33 to 40.

Flood Impacts
37.29 Feet	Stages above 37.3 feet results in flooding outside the levees. Top of levee.
29.6 Feet	Homes along east bank of river on Airport Court in Manteca experience flooding.
26.0 Feet	Severe seepage occurs outside the levees. The area covered by seepage will increase as the river stage rises.
24.5 Feet	Monitor Stage - water reaches the toe of levee.
21.0 Feet	Seepage begins into crop area outside of levees.

Product Disclaimer

This river graphic is not intended to serve as a substitute for official flood watches, warnings, advisories, or statements issued by the NWS Sacramento Weather Forecast Office. Observations are preliminary and subject to change. River levels identified as "forecast" should be consistent with those contained in official NWS products. River levels identified as "guidance" have significant uncertainty due to future weather or reservoir regulation and are provided for planning purposes only.

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