The last few patches of snow are clinging to the north faces of the Sierra Nevada's Carson Range as temperatures rise to 100 degrees and hotter.
Photo by Kurt Hildebrand.
By Kurt Hildebrand
Friday, July 5, 2024
It’s not just hot in Carson Valley, it has also been extremely dry, with the last measurable rainfall in Minden recorded on May 14.
While dry conditions help when harvesting, those same conditions make it harder to grow hay.
Key to Carson Valley’s agriculture are rights to irrigation water in the Carson River, which officials with the Carson River Subconservancy has been slowly decreasing over the year.
Executive Director Ed James said work on a 30-year Watershed Regional Drought and Water Sustainability Plan is underway.
The plan will combine data gathered by the subconservancy and information from the various water purveyors in the watershed.
James said that work will also be shared with the U.S. Geographical Survey, which is currently conducting a study specific to Carson Valley.
“This is not a master plan,” he said. “It’s just providing additional information to those purveyors as they plan for the future. Most entities know what they want for their local area. What we’re doing is providing information that’s outside of the local area so they can do better planning for the future.”
He said it’s also not designed to take anyone’s water rights or propose any changes to either Nevada water law or the Alpine Decree, which divides the river into segments and establishes water rights priorities.
James said a review of water use in the Valley comparing 1974-1941 with 1975-2009 showed that flows on the river at the Carson gauge near Prison Hill indicated levels that were historically higher in June and July have shifted to March, April and May. That’s important because irrigation season begins April 1 and may be the result of warmer temperatures.
“If you look at March, the later dates show more flow occurring than there was historically,” he said. “There’s a shift in runoff on the Carson. That water is coming down faster and sooner. It benefits the Lahontan reservoir because Lahontan fills in the winter and springtime.”
There isn’t a reservoir or other manmade structure to capture water upstream from Carson Valley when irrigation water dries up.
He said ranchers have two choices, either to pump more water when it’s dry or to not irrigate and leave fields fallow.
“It’s something we can’t control,” he said. “The East Fork has very little manmade impacts upstream from us, so this is what Mother Nature is giving us today.”
And according to records, increasing agricultural pumping also increases the draw on the Valley’s aquifer.
There are an estimated 100,000 acre feet of recharge in Carson Valley and supplemental agricultural water rights account for around half of that.
Municipal water use accounts for around 13,000 acre feet while agricultural irrigators have pumped anywhere between 5,000 in wet years and 18,000 acre feet in dry years between 2007 and 2020.
Domestic wells in the Valley are fairly stable at around 4,000 acre feet, according to information prepared by Lumos and Associates.
“Surface water and ground water use goes up and down basically on wet or dry years,” James said. “In 2011 it was a very wet year. Then in the years 2014-15, it was a very dry year, and we see the see total demand in the groundwater go up.”
Despite an average winter there were above average flows on the river compared to the historic average, before it dropped to below average runoff in June.
He said that the Subconservancy believes Carson Valley will see an additional pumping of 1,700 acre feet over the next 30 years.
Overall, water pumping in Carson Valley is rising on average over time with 30,000 acre feet, up from around 27,000 acre feet in 2007.
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