CNRFC - Hydrology - River Guidance - Graphical RVF

*** IMPORTANT *** Week of June 16 - Website Data Outage - Due to a major computer upgrade the week of June 16, nearly all data on the CNRFC web site will not be updated. We anticipate the down time to be approximately 4 days. The latest deterministic hydrologic forecasts for official forecast points will continue to be available at the National Water Prediction Service during this time.

Location:

WALKER RIVER - MASON AT SNYDER LANE (MASN2)

Latitude: 38.92º N	Longitude: 119.19º W	Elevation: 4420 Feet
Location: Lyon County in Nevada		Bulletin Group: Eastern Sierra		River Group: Eastern Sierra

Issuance Time:

Jun 16 2025 at 6:18 AM PDT

Next Issuance:

Jun 17 2025 at 9:00 AM PDT

Action/Monitor: 9.0 Feet

Minor Flood: 9.8 Feet

Moderate Flood: 11.0 Feet

Major Flood: 11.6 Feet

Please Note:

Significant losses can occur in the Mason Valley upstream of the Mason stream gage. Increased forecast uncertainty exists in the long range forecast due to these unknown losses.

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
Water Year	Peak Discharge (cfs)	Stage (feet)	Date
Most Recent 5 Years
2024*	917	6.69	Jun 8, 2024
2023*	3,810	11.64	Jun 8, 2023
2022*	321	5.48	May 30, 2022
2021*	316	5.48	May 11, 2021
2020*	335	5.62	Oct 8, 2019
Historical High Stage/Flow Events (Period of Record - April 1974 to Present)** - Ranked by Flow
1997*	3,900***	12.72	Jan 04, 1997
2023*	3,810	11.64	Jun 8, 2023
2017*	2,910	10.94	Jun 24, 2017
1995*	2,980****	11.57	Jul 11, 1995
1983*	2,790***	11.31	Jun 19, 1983
2011*	2,420	10.77	Jul 01, 2011
* Discharge affected by regulation or diversion.
** Break in data between Oct 1984 and Sept 2010.
*** Prior to Sep 30, 1984 - gage location 0.1 mile downstream at different datum.
**** Estimated using other gages and MASN2 rating #5.1

Location Photographs
Upstream Photo	Gage House Photo	Downstream Photo

ESRI™ Locator Map

Flood Impacts
13.0 Feet	Near record flooding in the Mason Valley-Yerington area. Significant flooding of homes and businesses in Yerington possible if breaches develop and the river spreads east. Extensive flooding of agricultural lands likely. Many primary and secondary roads flooded.
12.5 Feet	Major flooding in the Mason Valley-Yerington area. Extensive flooding of farm and pasture lands. Many roads flooded. Some portions of Yerington flooded if breaches develop and the river spreads east.
12.0 Feet	Major flooding in the Mason Valley-Yerington area. Some portions of Yerington flood if breaches develop and the river spreads east. Many roads flood. Extensive flooding of farmland and pasture near the river flood.
11.6 Feet	Major flooding of lowlands throughout the Mason Valley-Yerington area. Structures adjacent to river in floodplain may be damage if not protected. Mason Valley Widlife Management area likely inaccessible. Flooding of many secondary and some primary roads occurs.
11.3 Feet	Moderate flooding of lowlands to farm and pasture lands throughout the Mason Valley-Yerington area. Some low structures adjacent to river begin to flood. Several secondary and some primary roads flood. Exceeds flood peak of June 2017.
11.0 Feet	Moderate flooding of lowlands, pasture and farmland adjacent to river throughout Mason Valley-Yerington area. Several rural and some secondary public roads flood. Yards and basements of lowest homes adjacent to the river in Mason and Yerington begin flooding. Preventative sandbagging is necessary. Possible damage to irrigation structures and levees Similar to June 24, 2017 peak, and slightly higher than July 1, 2011 peak.
10.8 Feet	Minor flooding of lowlands...pasture and farmland adjacent to the river throughout the Mason Valley-Yerington area. Some rural roads flood. Preventative sandbagging of low structures in Mason and Yerington may be necessary as river rises, but limited flooding occurs. Some minor flooding of basements and yards in Mason. Similar level to floods of July 1 2011.
10.5 Feet	Minor flooding of lowlands, pasture, farmland and some rural roads in Mason Valley. Preventative sandbagging of lowest homes in Mason and Yerington should be done as river rises, but limited flooding occurs. There may be some minor flooding of yards and basements in Mason.
10.3 Feet	Minor flooding of lowlands,pasture and farmland in Mason Valley-Yerington area. Preventative sandbagging of lowest homes and businesses adjacent to river should begin if further rises are possible. Some flooding of rural roads, likely including Miller Lane.
10.0 Feet	Minor flooding of lowlands, pasture, cropland and some rural roads throughout the Mason Valley/Yerington area. No flooding of structures.
9.8 Feet	Flood Stage, Minor lowland flooding begins throughout Mason Valley-Yerington area, with some inundation of lowlands and rural roads.
9.0 Feet	Monitor Stage, near bank full conditions. No flooding in the Mason Valley-Yerington area.

Official 7 Day National Weather Service Forecast (NVZ001)

Today: Sunny. Highs 84 to 94. West winds around 10 mph increasing to 15 to 25 mph with gusts up to 40 mph in the afternoon.

Tonight: Clear. Lows 50 to 60. West winds 20 to 30 mph with gusts up to 45 mph becoming northwest 10 to 15 mph after midnight.

Tuesday: Sunny. Highs 82 to 92. Northwest winds 10 to 15 mph.

Tuesday Night: Clear. Lows 55 to 65. Northwest winds 10 to 15 mph.

Wednesday: Sunny. Highs 90 to 100. Light winds becoming north around 10 mph in the afternoon.

Wednesday Night: Clear. Lows 58 to 68.

juneteenth through Friday Night: Breezy, clear. Highs 90 to 100. Lows 54 to 64.

Saturday through Sunday: Breezy, clear. Highs 75 to 85. Lows 41 to 51.

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 Reno 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
Month:	Day:	Year:	Cycle:
To view other verification locations, use our Historical Graphical River Forecast Interface.