Guest opinion: Northern Water did what it could to minimize flooding
General Manager, Northern Water
Although this year’s record-breaking snowpack and streamflows made for an impressive display of Mother Nature’s capabilities, they also posed concerns for property owners along streams, including the Colorado River below Lake Granby, a Colorado-Big Thompson Project reservoir.
Under federal authorization, the C-BT Project is not a flood control project. However, years come when operators still have the opportunity to reduce flooding.
This has been one of those years. As the snow piled high this winter, Bureau of Reclamation and Northern Water forecasters and operators began talking about how to make downstream flows manageable and less damaging once runoff hit.
Federally-developed standard operating procedures call for Lake Granby to rise to six inches below full, at 8,279.5 feet in elevation, and then spill or release all incoming flows back to the Colorado River. Forecasters suspected this year’s record-shattering snowpack would result in significant inflows that would make this procedure cause higher downstream flows than alternative operations that could reduce flooding.
They were right. The flows in the Colorado River above Lake Granby from April through July reached 195 percent of average, producing 429,000 acre feet, shattering the 1984 record of 355,000 acre feet. For perspective, 429,000 acre feet could fill 92 percent of Lake Granby’s active storage capacity.
Reclamation and Northern Water modified normal procedures and made extra storage space available ahead of peak runoff by releasing water out of Willow Creek Reservoir and Lake Granby. These pre-emptive releases meant downstream residents saw steadier, lower river flows over a longer period of time. As runoff peaked, the amount of water released from Lake Granby topped out in late June at about 2,300 cubic feet per second, and we reached that rate again in mid-July after rainstorms produced inflow peaks for the second time.
Without these modified operations, downstream residents would have seen flows hit high, hard and fast, reaching about 3,900 cfs in early July. If operations had not been modified, the outflow would have exceeded 2,500 cfs for nearly 20 days, creating the potential for sustained flooding. As it was, we exceeded 2,000 cfs for only 10 days.
We will continue to make higher-than-normal Lake Granby releases through mid-September to allow water levels to drop to lower winter season levels to prevent freeze damage to facilities. We are coordinating these releases with the Colorado Division of Wildlife to prevent impacts to brown trout spawning.
The two purposes of the C-BT Project are to provide water for agricultural, municipal and industrial use and to generate hydroelectric power. In our operating partnership with Reclamation, we strive to continually meet these Congressionally-authorized needs. We also understand residents’ concerns about flooding. In response Northern Water and Reclamation worked diligently this year to balance rapidly-changing conditions with required operations, keeping our neighbors in mind.
Eric Wilkinson has been Northern Water’s general manager for 17 years and has spent the last 30-plus years working in water resources management in Colorado.
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