CNRFC - Hydrology - River Guidance - Graphical RVF

Location:

SAN JOAQUIN RIVER - VERNALIS (VNSC1)

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

Issuance Time:

Dec 26 2025 at 2:51 PM PST

Next Issuance:

Dec 27 2025 at 9:00 AM PST

Action/Monitor: 24.5 Feet

Minor Flood: 29.0 Feet

Moderate Flood: 32.0 Feet

Major Flood: 37.3 Feet

Plot Type:

Please Note:
1) Each individual timeseries plotted on the graphical river forecast can be toggled on and off by clicking the legend entry above. If the "Observed (Raw Data)" contains bad data and is toggled off, the plot will scale to the remaining timeseries.

2) At extremely low river flows, the "Observed (Raw Data)" may show readings below the lower end of the available rating table, while the "Observed (Simulated)" will only show values at the bottom of the rating table, creating a potential discrepancy between the two readings.

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

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.

Official 7 Day National Weather Service Forecast (CAZ019)

Tonight: Mostly cloudy. A chance of rain until early morning. Lows 41 to 46. Southeast winds 10 to 15 mph with gusts to around 25 mph.

Saturday: Partly cloudy. Highs 48 to 53. Southwest winds up to 10 mph shifting to the northwest in the afternoon.

Saturday Night: Mostly cloudy in the evening then clearing. Patchy fog after midnight. Lows 36 to 41. Northwest winds up to 10 mph.

Sunday: Mostly cloudy in the morning then clearing. Patchy fog in the morning. Highs around 48. Light winds.

Sunday Night: Mostly clear in the evening then becoming mostly cloudy. Lows around 37. Light winds.

Monday: Mostly cloudy. Highs around 48.

Monday Night: Partly cloudy. Lows around 38.

Tuesday: Mostly cloudy. Highs 47 to 53.

Tuesday Night: Mostly clear. Lows around 39.

Wednesday: Mostly cloudy. Highs 47 to 53.

Wednesday Night: Mostly cloudy with a slight chance of rain. Lows around 42.

New Years Day: Mostly cloudy with a chance of rain. Highs around 50.

Thursday Night: Cloudy with a chance of rain. Lows around 45.

Friday: Mostly cloudy with a chance of rain. Highs around 52.

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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Verification - Historical Graphical RVF
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To view other verification locations, use our Historical Graphical River Forecast Interface.