Cool spring has kept mountain melt-off on ice
The second half of April is typically when the Carson River begins to see peak runoff, though that might not be true this spring.
The West Fork at Woodfords is expected to rise above the monitor stage of 12.5 feet late Saturday night by a couple of inches. Flood stage on the West Fork is 13.5 feet.
The senior partner in the Carson River, the East Fork, is expected to remain well short of the 13-foot monitor stage, rising to 11.9 feet by 1 a.m. Sunday.
Flood stage for the East Fork entering Carson Valley is 14 feet.
So far, snowpack in the Carson River basin is running about twice average for this time of year.
Ebbetts Pass, at the headwaters of the East Fork, has 62.4 inches of water locked in the snowpack. Carson Pass at the top of the West Fork has 50.4 inches of water in the snowpack, according to Natural Resources Conservation Service data.
In a report written by Carson Water Subconservancy District Watershed Program Specialist Shane Fryer, the snow-water equivalence this year is in the upper 10 percent.
“Compared with the past 30 years of data, the Carson is ranking very high in available water,” he said.
While 2019 has been very productive, it doesn’t compare with the levels reached in the record year of 2017.
While precipitation hasn’t been that substantial, cold weather has helped keep the river’s main source of water on ice, so far this year.
Fryer points out that average temperatures this year have been below the 30-year average.
“If this cold trend continues into spring, we could expect a delay or a longer duration spring runoff with reduced peak flow,” he said.
Preparation for flooding along the river has been ongoing since 2017, and included clearing and snagging near the major bridges in Carson Valley.
Stormwater Manager Courtney Walker said work to increase channel capacity on Cradlebaugh Bridge, where the East Fork crosses Highway 88 and Lutheran Bridge wrapped up in November.
More than 18,800 cubic yards of material was removed from the river, costing $490,000.
“I believe this slough being full of debris and willows may be the reason Highway 395 did close a couple of times during flood events in 2017,” Walker said.
Similar work done downriver from Riverview in the Gardnerville Ranchos was credited in reducing flooding near Carson Valley Golf Course in 2017.
Work was coordinated by the Carson Valley Conservation District, with help from the county, the subconservancy and the Nevada Division of Water Resources.
While spring is a key source of river flooding, there are fewer means of predicting flash flooding that occurs out of the Pine Nuts during the summer.
El Niño years have seen more monsoonal flow into Western Nevada during the summer. Flash flooding that struck Johnson Lane and Fish Springs in 2014 and 2015 were in a run-up to or during an El Niño year.
A weak El Niño has developed during the winter of 2018-19 and if forecast to continue into the summer.
El Niño is a large-scale warming of ocean surface temperatures across the central and east Central Pacific.