The poor 2009-10 winter is taking its toll on Magic Reservoir, a popular fishery and boating destination in southern Blaine County that's also an important supply of irrigation water to downstream users.
The best the manmade water body can expect this summer is to reach about three-quarters of its normal full capacity, the USDA Natural Resource Conservation Service states in its May 1 "Idaho Water Supply Outlook Report." The agency goes on to say that the reservoir will look much like it did during the most recent year of greatly decreased water flows on the Big Wood River system.
"Magic Reservoir is 70 percent full and will not fill," the report states. "Shortages are expected and water supplies will be similar to those in 2007."
Elsewhere across Idaho, the water supply picture is better at many reservoirs. That includes other nearby water bodies like the Little Wood and Mackay reservoirs, which are both seeing nearly full conditions due to carryovers from last year.
Of Idaho's 28 major water storage facilities, 22 were reporting average or better water conditions on April 30. The cool, wet weather that the state received in late April helped delay the snowmelt, which should help many Idaho irrigators this summer.
According to the Natural Resource Conservation Service, the cool weather of late April held off the region's snowmelt and even added to local mountain snowpacks. Despite below-average river flows in Idaho, that will allow irrigators to water their crops later in the season because the snowmelt has been delayed.
"If the cool and wet conditions had not occurred in April, snowpacks across the board would have melted out much earlier," said Ron Abramovich, a water supply specialist for the Natural Resource Conservation Service. "Rivers would have peaked too soon."
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Abramovich said most of Idaho's irrigators should be able to make it through the season. He said some surface water shortages are likely in central and southern Idaho basins, including the Big Wood, Big Lost, Little Lost, Oakley and Salmon Falls drainages and for users that rely on natural stream-flow levels for irrigation needs.
April precipitation was above average across most of the state, the Natural Resource Conservation Service reports. Monthly precipitation ranged from 94 percent of average in the Big Lost River basin east of the Wood River Valley to 140 percent of normal near the headwaters of the upper Snake River and the Bear River drainage in eastern Idaho.
Current snowpack levels across Idaho are a mixed bag—running anywhere from 45 to 85 percent of normal. In many spots throughout Idaho, low-elevation snowpacks were already melted by mid-April. Though snowmelt began in higher elevations in early April, the cool temperatures the state received in late April combined with precipitation temporarily halted the melt and even added water content to the snowpack.
Abramovich said there is still enough snow in the central, northern and upper Snake River basins to produce another peak in streamflows.
"Reservoir operators are hoping the peak streamflows occur when they normally do in the latter half of May, he said. "That way they can maximize water storage and delivery for all the various users."
Headed into the weekend, the National Weather Service is calling for highs in the 60s in the Wood River Valley with mostly sunny to partly cloudy skies. The weather service is calling for a return of cool, moist weather early next week.
Jason Kauffman: jkauffman@mtexpress.com
A dog plays in the shallow water along the east shores of Magic Reservoir on Wednesday. The USDA Natural Resource Conservation Service has said that boaters, anglers and other water users can expect Magic Reservoir to only fill to 70 percent of its normal capacity this summer due to below-average flows from the Big Wood River. Photo by David N. Seelig
