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Wyo H20 storage levels climb

by Wyoming Livestock Roundup

    Wyoming storage levels saw big benefit from the late-May spring storm that hit most of the state and the much-needed moisture has boosted crops and rangeland conditions moving into summer.
Storage levels
    Wyoming Bureau of Reclamation Area Manager John Lawson reported Buffalo Bill and Boysen reservoirs will fill and Pathfinder and Seminoe reservoirs have seen big improvements. He also says the storm increased almost all snowpack levels in the state’s basins.
    Lawson says he expects a higher-than-average runoff into Buffalo Bill for June and July. He is looking at 4,400 cubic feet per second (cfs) from the dam, which is “far above the irrigation demand.”
    Originally not expected to fill, Boysen is now expected to reach fill level. Lawson reports a release of 2,300 cfs from the reservoir and says the irrigation demand is only 1,200 cfs. Boysen’s release may move up to 3,000 or 3,500 cfs, while still retaining the ability to fill.
    “It’s good news to have this much,” Lawson says.
    An increased snow pack for Seminoe and Pathfinder reservoirs is also helping conditions. Lawson says the storm didn’t have as big of an effect on these reservoirs but with the above-average snowpack these two reservoirs will begin to see gains.
    Lawson cited National Weather Service information that reported eight inches of rain at Glendo in a five-day period and the rain increased inflows into Glendo Reservoir from 4,000 to 12,000 cfs. The influx of water filled Glendo into the exclusive flood pool; the added storage in the reservoir to catch flood flows. Releases from the flood pool later this month will assist in meeting downstream needs and Lawson says they haven’t seen these kinds of conditions for nine or 10 years. Lawson says he is also seeing similar activity on a smaller scale for Guernsey Reservoir.
    As a result, Gray Reef releases in the upper system were cut from 2,300 cfs to the minimum release of 500 cfs. Pathfinder and Seminoe outflows are also much less and outflows won’t increase again until the irrigators turn back on, which Lawson estimates won’t happen until mid-June.
    The good news keeps coming and Lawson says Pathfinder’s expected level this September is 271,000 acre feet. That compares to Sept. 30, 2007 where Pathfinder was only 17 percent full at 171,000 acre feet. Similar good news for Seminoe is expected as well with an estimated level this September at more than 400,000 acre feet.
    “This isn’t a complete recovery but it is sure welcomed,” Lawson says. “If we get a few more years like this we could be in great shape.”
    Moving into summer State Climatologist Steve Gray says we’ve had a better winter in terms of building snowpack than we have in the last eight to nine years and the cooler spring temperatures helped us hang on to the snow pack. Gray explained the state is at historical average levels but the levels are looking better than they have in a few years.
    Natural Resources Conservation Service snow-pack data indicates more than 100 percent of average snow water equivalent for all Wyoming basins as of June 3. The levels range from 133-270 percent across the state, according to the June 3 data, with an average of 132 percent as of May 26.
    Gray says the low country was having a fairly bad spring, particularly the Western part of the state, which was at only 25 percent or lower of historical averages for moisture. However, the storms at the end of May brought enough moisture to the majority of the state to get back to historical averages for spring.
    “It looks like the moisture might have come just in time to turn things around in the low country,” Gray says.
    Depending on future conditions, the moisture could mean different things for the state. Gray says the state is starting with an average spring in terms of total amount of precipitation received. “Average” may sound strange given the amount of moisture received, but Gray says historical averages from 1970 to the drought put the numbers at about average. But Gray also says in the context of the last seven to nine years of drought, the state is in good shape going into the summer season. Gray says conditions could worsen if the weather produces a string of hot, windy days but conditions may see additional improvements if Wyoming receives more spring and summer thunderstorms.
    “The summer is starting out better than we have in recent years but the true nature of it is yet to be determined,” Gray says.
    Liz LeSatz is summer 2008 intern for the Wyoming Livestock Roundup and can be reached at

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