Friday, April 4, 2008

Idaho water reserves look good

Forecasters say recent cool, wet weather helped boost snowpacks

Express Staff Writer

Because of the cool, wet weather the region received in past weeks, streamflows will likely be around normal on the Big Wood River and other area waterways this spring and summer, the National Weather Service has predicted.

    The mountains may not realize it yet, but spring has arrived in Idaho.
    On Tuesday, the state’s water season officially began. State hydrologists consider the Idaho water season to run from April 1 through Sept. 30.
    Every winter, Idaho farmers, hydrologists and wildfire officials anxiously track snow depths in the state’s backcountry to see what kind of runoff will occur during the warmer months ahead. For the most part, Idaho’s irrigators rely on higher-elevation snowpacks to fill the state’s reservoirs and rivers. Lower elevation snowpacks generally melt out in April and May.
    Yesterday, Thursday, April 3, the Pocatello office of the National Weather Service released its eastern Idaho weekly hydrological update.
    The report said the cold, wet weather Idaho has recently received has added “a well-needed boost” to eastern Idaho snowpacks. The NWS said the weather brought a 2 percent increase in average snow-water equivalent in the 10 eastern Idaho river basins where the Natural Resources Conservation Service tracks snow depths.
    The NWS said this finally put the average snowpack in the 10 basins above normal, to 102 percent of average, based on NRCS data. Of the 10 basins, the Blackfoot and Portneuf basins in extreme southeastern Idaho received the biggest boost, with an average 5 percent increase, the NWS said.
    The Henry’s Fork and Teton basins also received a big boost of about 3 percent.
    And for the first time in weeks, none of the 10 eastern Idaho basins lost anything in the way of snow depth, the NWS said.
    Looking forward to the next seven-day period, the NWS said the next Pacific weather system will move onshore today.
    “Some precipitation will move into the central mountains late in the day Friday and spread over the remainder of southeast Idaho Friday night,” the NWS report states. “A cold front will move through Idaho Falls and Pocatello around midnight Friday night, bringing light snow to the valleys and two to five inches in the mountains.”
    The NWS added that another weather system will move through southern Idaho between Sunday morning and Monday morning with 2 to 4 inches of snow possible in the mountains.

    Based on online data provided by the NRCS, the snowpack in the Big Wood basin, which includes the Wood River Valley as well as the Camas Creek drainage in the Fairfield area, was at 101 percent of average on Thursday.
    The figure is calculated by averaging the snow-water content of nine Snotel sites in the Big Wood basin.   
    Short for snowpack telemetry, Snotel sites relay a vast array of weather data from remote mountain sites to Idaho’s NRCS headquarters in Boise. Snotel evolved from a NRCS congressional mandate in the mid-1930s to measure Western snowpacks in order to forecast water supply. Today, there are 83 individual Snotel sites throughout Idaho’s mountains.
    Snowpack readings in the Big Wood basin over the past few months show fluctuations in their percentage of normal. The snowpack was 110 percent of average around the beginning of February but just 96 percent of average by mid-February.
    This year’s snowpack depths in the Big Wood basin are a far cry from last year’s, which reached a low of nearly 30 percent of normal last spring.
    For now, snowpacks in the 19 Idaho river basins measured by the NRCS look increasingly positive, with percentages ranging from a high of 124 percent of average in north-central Idaho’s Clearwater Basin, to a low of 91 percent of normal in the Big Lost Basin, just two drainages away from the Wood River Valley to the east.
    Overall, snowpack percentages in Idaho’s 19 measured river basins average about 106 percent of normal.

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