All aspects of irrigation are projected to be quite good this year, Idaho water officials say.
Lyle Swank, Idaho Water District 1 manager in Idaho Falls, said the snowpack is over 100% in all the vital areas. That adds onto the carryover water from last year bringing a much-needed opportunity to recharge the East Snake Plain Aquifer.
“Recharging the aquifer is done by letting water out into the canals before irrigation season begins to let that water filter back down into the ground,” Swank said. “Of course, once the weather heats up, the water will start being used for irrigation. Until then, this is a great way to recharge the aquifer. I’m glad we have enough water to be able to do that. It certainly needs to be recharged.”
Water left in the reservoirs last year also helps with the outlook.
“We had a very good carryover from 2018,” Swank said. “It was also a good water year. We had a couple really dry years in 2012 and 2013 when the water supply was seriously depleted but we’re looking a lot better now.”
Swank said the generous snowpack and rainfall are working well to reestablish water level throughout the area.
The period of using water rights began in mid-March for some areas and April 1 for others. However, most are not being used for irrigation yet. Full canals now are due to recharging.
All water right priorities are currently being filled as water is spilling past Milner Dam, according to the April 1 water report.
Irrigation water supplies for all of Idaho are looking very positive, said Ron Abramovitch, water supply specialist with the Idaho Natural Resources Conservation Service at Boise.
The Clearwater Basin is at slightly better than 40% of normal. Water amounts increased to 50% to 80% moving south, with southern Idaho having the most precipitation. Areas south of the Owyhee, Bruneau, Salmon Falls and Goose headwaters in Nevada and Utah had March precipitation totals of 150% to 200% of average.
“Streamflow forecasts decreased slightly from March 1 because of the below-normal March precipitation but still mirror the snowpack, increasing as you move from northern Idaho to southern Idaho,” he said.
February’s extra precipitation more than made up for March’s lower rainfall, Abramovitch said.
He said most farmers had already made their crop planning based on the current irrigation supply projections, which are quite positive for a full irrigation water supply in 2019.
The National Weather Service reported that March was drier than expected and April also could be drier than usual. However, heavy snowpack and rainfall have the water levels and reservoir levels looking very good, Abramovitch said.
The April 1 study released said the snow-water equivalent is 107% for the average median values for this time of year at SNOTEL sites in the Snake River Basin above the Palisades Reservoir. Henry’s Fork Basin is at 116% and Willow Creek, Blackfoot River and Portneuf River Basins are at 121% of average. The runoff forecast of the Snake River at Heise is 99% of average.
The study showed precipitation this water year, beginning Oct. 1, is closer to average than median snow-water equivalent, although some sites have reported lower than average precipitation totals since the water year began.
Higher-elevation SNOTEL sites, where snow is measured, are close to average while lower sites have higher levels. This increases the chances for a swift runoff as lower elevations melt.
“We are closely monitoring all our water sites,” Swank said. “So far, we feel very good about being able to manage the reservoirs and the runoff without serious flooding danger anywhere.”
The Upper Snake River Reservoir System has a capacity of 4,172,708 acre-feet. It is currently at 3,479,224 acre-feet as of April 2.
Of course, Mother Nature is always a factor to be reckoned with.
“How much more precipitation we get has to be considered,” Swank said. “And, the temperatures determining how fast the snowpack melts also are important factors. We keep a very close eye on all the elements related to the reservoirs and runoff. Still, we’re feeling pretty confident we’ll be able to manage any potential flooding. It’s all part of the annual challenge.”