Snowpack, water supply looking good - for now

The U.S. Department of Agriculture has released its most recent Idaho Snowpack and Water Supply Outlook Report, which shows that the state is on track to replenish its water supply.

 The report, however, comes with a caveat – we were in the same position now as we were this time last year.

 “Despite the warm October, a cold November and December helped bolster Idaho’s snowpack to above normal levels,” according to the Jan. 1 report. “Although there are still several months left in the snow accumulation season, the snowpack through much of the state is already halfway to reaching normal peak snowpack conditions. The 2023 water year is off to a good start, but last year serves as a good reminder that continued snowfall is required to reach normal peak snowpack conditions and ensure adequate springtime runoff.”

 Most of the annual streamflow in the western U.S. depends on accumulated snowfall in the mountains during the winter and early spring. As the snowpack accumulates, hydrologists estimate the runoff that will occur when the snow melts using data collected at SNOTEL and other sites.

 “We love to start the new year off with good news; the snowpack is well above normal throughout the state,” the report states. “However, a strong sense of déjà vu permeates water year 2023; we are in the similar situation as last year. In order to fully recover from the drought, we need an ample snowpack to replenish depleted reservoirs and provide sufficient springtime natural streamflow before irrigation deliveries begin.”

 More than 70 percent of surface water supply comes from snowpack, but there are other factors in addition, including spring precipitation (rain), timing of the snowmelt, soil moisture and groundwater conditions.

 Last winter, southwest Idaho received above normal snowpack, but a warming trend melted much of it early, which ultimately led to a water shortage during the 2022 growing season. Water levels at Crane Creek and Mann Creek reservoirs were so low, the Weiser Irrigation District was forced to impose alternating watering schedules. The reservoirs ran out of water early, leaving users dependent on what was left in the Weiser River.

 In the end, there was enough water for everyone, but resources are drained and what will happen this summer depends, of course, on how much snow and rain the area receives between now and spring runoff.

 The first part of January was expected to be wetter than normal, with that prognostication coming true.

 The Idaho SNOTEL water year, from Oct. 1 to present, puts Weiser at 131 percent normal precipitation, with most of Idaho at or exceeding normal. Payette sits at 117 percent and Boise at 128 percent, while areas in southeast Idaho range from 120 percent to as much as 172 percent of normal.

 According to the National Weather Service, the precipitation outlook puts southwest Idaho between the normal to above normal range for the remainder of January and into February.

 According to almanac.com, much of Idaho’s long-range weather, “will be warmer than normal, with the coldest periods in mid-November and early February. Precipitation will be above normal, with above-average snowfall in the far north and far south. The snowiest periods will be in mid-November, late December, early to mid-January, and early February. 

 “April and May will be cooler than normal, with above-normal precipitation, on average. Summer will be slightly cooler than normal, with rainfall above average in the north and below normal in the south. The hottest periods will be in mid- to late July and early August. September and October will be cooler and drier than normal, on average.”