Soggy June pumps up reservoirs

Utah has finished its fourth wettest water year in the past decade, and its reservoirs are holding more H2O than they have in 10 years.

As the water year ended Wednesday, Utah completed a close to average year for total precipitation, according to Todd Adams, Division of Water Resources assistant director.

Utah's statewide total precipitation (measured at 77 mountain "snotel" sites) for the 2009 water year will likely fall just short of the 30-year average but is significantly higher than the past 10-year average. In the past decade, only 1999, 2005 and 2006 were wetter than 2009.

Averaging Utah's 13 water basins together yields a statewide average of almost 96 percent for the past water year. (The figure is slightly skewed due to overlap in some of the basins.) The water years runs from Oct. 1 to Sept. 30.

Despite the good overall picture for the state's water supply, Adams stressed that Utah is the second-driest state in the nation.

"Conservation is a long-term ethic," he said. "We need to practice it always."

The key factor for the 2009 water year was the moisture-laden month of June, the second-wettest June ever in parts of the state. For example, the Salt Lake International Airport had average temperatures almost three degrees below normal and received 2.64 inches of moisture — 343 percent of normal.

June does not typically contribute significantly to the season's runoff and total reservoir storage. This year's June precipitation, however, accomplished two things. First, it delayed reservoir withdrawals around the state, with many areas receiving adequate rainfall to meet farming requirements. Second, the cool, wet conditions improved the efficiency of the runoff, helping most of the state's reservoirs to fill.

With efficient runoff and reduced irrigation demand, reservoirs held up well through the summer irrigation season. Statewide, reservoirs are currently at about 67 percent of capacity. That is a much better statewide average for this time of year than Utah has experienced in the past 10 years and slightly higher than the long-term average.

Almost half of the 33 percent of unfilled storage capacity is in one reservoir: Bear Lake.

"It's just a big hole," Adams said of the lake, which is more than 200 feet deep when full.

Irrigation users were granted the use of 209,000 acre-feet of water out of Bear Lake this year but only had to use 50,000 or less because of the cool, wet start to summer, he said. Bear Lake currently has approximately 170,000 acre-feet more water than it had at this time last year.

That is an increase of 60 percent over last year's storage at the end of September. Still, Bear Lake is well below full and will need several more good water years to fill completely.

All other reservoirs in the northern portion of the state benefited from the wet June conditions and are in good shape.

The central and southern portions of the state have not fared quite as well. In the Sevier region, most reservoirs are slightly below their carry-over storage at the end of last year's irrigation season and significantly below their long-term average. Most of the reservoirs in the southwest and southeast portions of the state are close to last year's end-of-the-year supply and close to their long-term carry-over averages.

e-mail: lynn@desnews.com