Experts: dry winter months to affect summer water supply
Two months of below normal precipitation in most parts of Idaho are likely to affect water supply according to the most recent report released this week by the Natural Resources and Conservation Service.
“The snowpack is lagging from below normal precipitation in January and February. If March is dry that will affect streamflow forecasts,” said Ron Abramovich, Idaho NRCS Water Supply Specialist. Currently, the majority of streams in the state are forecast in the 70-90% of average range.
“We’ve learned from the past that when we get two dry winter months in a row, negative impacts on the water supply start to occur,” Abramovich said. “Abundant March precipitation would help but short of that, preserving the snow that already exists is the best we can hope for.”
High elevation snowpack is adequate and carrying the snowpack average. The low elevation snowpack lacks volume and will melt out quickly as seasonal temperatures increase.
“Knowing what elevation your water supply comes from will help you prepare for this season’s water supply,” Abramovich said. “Lower elevations will melt out sooner and runoff will be low translating to a decreased water supply.”
Abramovich pointed out, this year, NRCS switched to a new time period to calculate normal snowpacks. Percentages may seem higher than last year because the new normals for the 1981-2010 period are lower than the 1971-2000 period. The new normals allow comparison to the most recent climatic norms. Comparing the actual water content of the snowpack (the snow water equivalent) provides a true measure between years; a link to this data is available in the March Water Supply Outlook Report.
The complete March 2013 Water Supply Outlook Report is available online at www.id.nrcs.usda.gov/snow and click on the ‘March 2013 Water Supply Outlook Report’ link. The report includes snowpack, precipitation, runoff, and water supply information for specific basins.
NRCS conducts snow surveys at the end of each month from December through May to make snow runoff predictions and water supply forecasts used in managing Idaho’s water resources.