Courtesy
An aerial photo of Mason, Nev., taken over the Memorial Day weekend, shows the extent of the flooding. Mason is an unincorporated community in Lyon County about four miles south of Yerington. Courtesy photo - City of Yerington Public Works
Sunday, June 4, 2023 | 2 a.m.
Members of the Walker River Paiute Tribe in Northern Nevada have placed sandbags around their houses and wrapped them in plastic sheeting to prepare for flooding from what is projected to be the highest recorded water levels in the Walker River since 1906.
Historic snowpack is melting and dumping a record amount of water runoff in northern and western parts of the state. The onslaught is filling rivers and streams and overwhelming some properties while residents brace for the flooding to peak.
The three major watersheds fed by the Sierra Nevada mountain range — the Truckee, Carson and Walker rivers — are receiving snowmelt 270% to 380% above the 30-year median, according to the National Resource Conservation Service.
In response, eight Nevada counties and two tribal governments last week passed emergency declarations, and Gov. Joe Lombardo signed a state of emergency to allow affected counties and tribes to be eligible for federal assistance to repair damaged infrastructure and mitigate further flooding.
“We’re not flooded yet, we’re just expecting it,” said Jefferson Emm, a manager for the Walker River Paiute Tribe’s environmental department.
Emm said the tribal staff formed an emergency sandbagging workforce to make sure all residents were prepared. Nevertheless, the tribal council has requested a sandbagging machine and other assistance from the federal government, he said.
“There isn’t a single person alive on the planet that would be able to tell us what to expect to experience,” Emm said.
There are three reservoirs on the Walker River system: Bridgeport, Topaz Lake and the Weber, which is on the Walker River Paiute reservation. The reservation is at the tail end of the river, protected from floodwaters by the Weber Dam.
Snowmelt from the Sierra Nevada mountain range flows into the Bridgeport Reservoir first, which is at 26% capacity in anticipation of more water to come. From there it flows to the Topaz Lake Reservoir, at 43%, and finally to the Weber Reservoir.
Nearby Lyon County, which partially overlaps with the reservation, has already seen its fair share of flooding.
Emm said in Mason Valley, floodwaters have started to creep up porch steps and reach houses. Miller Lane, a major shortcut through the valley in Yerington, has been closed off because of flood water, increasing travel time through the town by about half an hour.
A home is encroached upon by floodwaters near the Mason Bridge in Mason, Nev. last month. The area could have been further inundated if not for the removal of a tree that was blocking the culverts under the bridge. - Photo courtesy of Taylor Allison, emergency/communications manager for Lyon County office of Emergency Management
Taylor Allison, emergency manager for Lyon County, said the California Nevada River Forecast Center and Walker River Irrigation District predicted a peak flow between 3,900 and 4,200 cubic feet per second, similar to the 1997 flood that inundated Yerington.
“The difference between the 1997 flood and our current situation is that the flood was only about a four-day event in January, and this is going to be a prolonged event,” she said.
The county has been working with Peri and Sons Farms and the irrigation district to build up the banks of the river near Yerington. Allison said that should hopefully protect irrigation drains east of the river, which can only handle about 400 cubic feet per second.
The second priority, she said, is protecting Yerington’s sewer system. She said residents on the west side of the river had been sandbagging their homes as well.
“We would see that flow for a good six to seven weeks, and we absolutely don’t want to see that happen,” Allison said.
Monitoring the flows should give residents and emergency management one to two days of warning before the peak comes. She said the timing could vary, but that peak is estimated to hit in mid-June.
The Bureau of Indian Affairs projects the Walker River’s flow through the Walker River Paiute Tribe’s reservation could reach 4,500 cubic feet per second at some point in June. Emm said the tribe was preparing for a 5,000-cubic-foot-per-second event, just in case.
In that scenario, about 20 homes and businesses would be in the flood’s path. Emm said property and business owners are preparing for what’s most likely headed their way.
If the irrigation canals just south of the Weber reservoir flood, they could send water straight into the reservation’s town. Emm said the Bureau of Indian Affairs is workshopping ways of blocking off or digging out the canals in that scenario.
“Certainly there’s several fields that are already going to get drowned out by this flood, but if it were to beach the head gates at the canal … there’s nothing really in the way to stop it,” Emm said.
Emm said the Bureau of Indian Affairs’ last inspection of the dam revealed gaps in the spillway that could let water in and erode the dirt below it. The bureau will monitor the dam around the clock, he said.
If the spillway were to erode, the Bureau of Indian Affairs could close it and instead open a smaller emergency spillway designed to erode away and let water through should the dam ever reach maximum capacity.
If the dam were to fail, over 71,000 cubic feet of water per second would flood the town in about 90 minutes, but Emm said that’s extremely unlikely.
“The last update on the dam suggests it’s doing its job perfectly,” he said. “Before the dam would ever have a chance to fail, that other emergency spillway design would take place.”
Emm said the reservation’s agriculture is mostly alfalfa, which requires irrigation to grow but will die off if submerged by floodwaters for too long. Irrigating during the hottest summer months is also tricky, he said, because alfalfa can cook in the water under high heat.
“I think it’s reasonable to expect a lot of the lower-lying fields are going to get impacted,” Emm said.
Jeff O’Connell, a forest hydrologist with the U.S. Forestry Service, said this year’s snowmelt has already exceeded snowmelt in 1983 and 1997, other notable flood years. O’Connell said most of Nevada has already seen peak runoff, but areas influenced by the Sierra Nevada snowmelt most likely have a few weeks to go.
O’Connell said the wildland urban interface — those places where the forest ends and private development begins — have begun flooding in his region and throughout the West.
“This is everywhere from Salt Lake to Denver, where we’ve encroached on natural ecosystems that we can’t help,” O’Connell said. “We should expect, whether it be interactions with wildlife or Mother Nature or flooding, that it’s going to happen.”
A new regimen designed to address wildfire risks, which he called “beyond historic,” may worsen flooding since it has altered landscapes that for years had been adapted to cope with flooding. New trails, roads and grazing livestock all create new conduits for runoff that didn’t exist previously, he said.
Jeff Anderson, a snow surveyor for National Resources Conservation Service, said the snowmelt runoff may likely roll over soil starved of moisture from the prolonged drought and keep going rather than sink in and stave off future fires and replenish groundwater tables, he said.
“We’re hoping, and anticipate, that we’ll get a slower melt,” Anderson said. “That’s the key to it, get a slower melt off of some of these high snowpack areas. … We want it to sink into the ground and let those grasses grow.”
Recreation in the region’s forests and parks has been affected too. High flows mean lots of fallen trees and branches are in the water.
Hiking and biking trails are thawing out, but slowly, he said.
“This time last year we probably had about 80% of our campgrounds open and people recreating, this year, it’s 20%,” Anderson said. “They can’t get out there and do the things they’re used to doing, and when they step into these rivers and think they’re safe …it’s really not that safe at all.”
Anderson said he didn’t anticipate many accidents, but under this season’s conditions visitors need to be aware of how quickly they could be swept away by rushing waters cold enough to cause hypothermia.
“We’ve had some rescues here on the Truckee River by our local fire department, getting people out of the water,” Anderson said.
Parts of a forest can also dry out quickly on the heels of flooding, making fire prevention just as serious as it is every year.
Still, O’Connell said in the long term, the snowpack and its flooding will make a positive difference in future fire seasons.
“It’s all a net positive; people just have to be patient,” O’Connell said.
