By Todd Neeley
DTN Staff Reporter
OMAHA (DTN) -- The historic Missouri River basin flood of 2011 was essentially unavoidable, and the U.S. Army Corps of Engineers did everything it could to control flooding and to manage water supplies during the 2012-2013 drought, the Government Accountability Office concluded in a new report. GAO said there were "no obvious deficiencies" identified and recommended no changes to the Corps' master manual.
While the GAO's lone recommendation is for the Corps to evaluate the pros and cons of incorporating new forecasting techniques into its management of the basin, the report said, "experts agreed that no existing forecasting tools, including those used by the Corps and NOAA (National Oceanic and Atmospheric Administration), could have accurately predicted the extreme rainstorms that occurred in Montana more than a week in advance.
"The December 2011 independent technical review panel report commissioned by the Corps also reached this conclusion, noting that accurate prediction of precipitation more than a week in advance is beyond the current state of science."
GAO said one expert it interviewed reviewed forecasting models available on March 1, 2011. It was determined that of the long-range forecast models available at the time, "only one forecasted a wet spring, and all other models forecasted normal or dry conditions.
"Based on the information the Corps had available in March 2011 -- these forecasts as well as evidence of the slightly above-normal mountain snowpack -- experts who participated in our meeting said they considered the Corps release decisions early in the spring to be appropriate."
In addition, GAO said experts it consulted were in agreement that the Corps could not have prevented the flooding.
"Snow continued to accumulate in the mountains in April and May -- well past the average date of maximum snow accumulation," GAO said. "The experts said that, by June 2011, the volume of water coming into the reservoirs from the extreme rains and melting snow was so great that the Corps had no choice in June and July but to release water to accommodate the inflow and prevent damage to dam infrastructure, such as spillways in danger of being overtopped."
A December 2011 report from an independent technical review panel reached a similar conclusion. That report said the absence of "major" dam failures indicates the Corps' success during the flood.
"Even if the Corps had decided on March 1, 2011, to increase releases due to the slightly larger-than-average snowpack in the mountains and plains, experts who participated in our meeting agreed that action would not have significantly reduced peak flows because of the extremely large amount of runoff in 2011," GAO said.
A group of nearly 200 farmers and other landowners sued the Corps of Engineers in March 2014, bringing claims that the Corps' management of the basin during the 2011 flood amounted to a taking of their property without just compensation.
In that lawsuit, the plaintiffs claim the Corps "departed from its longstanding management policies and practices when it knew that the direct, natural, probably, and foreseeable result of that departure would be increasingly frequent and severe flooding of plaintiffs' land and property."
One expert consulted by the GAO said the Corps would have needed "several months to release enough water" from the reservoirs to have space for runoff that occurred in 2011, and "predicting an extreme runoff year that far in advance is beyond the current state of science."
GAO interviewed 45 stakeholders from the Missouri River basin, including representing organizations in Iowa, Kansas, Missouri, Montana, Nebraska, North Dakota and South Dakota. Stakeholders included city government officials from communities along the river, state emergency management agencies, state fish and wildlife agencies and navigation industry representatives.
GAO said the basin's lowest runoff year was 1931, with 10.6 million acre feet of water. The highest runoff year was in 2011, with 61 MAF -- or enough to cover nearly the entire state of Oregon in one foot of water. GAO said that the previous-highest runoff in the basin was 49 MAF in 1997.
When it comes to the 2012-2013 drought, GAO said the same experts it consulted "agreed that the Missouri River basin's rapid descent into drought could not have been predicted." In particular, one expert consulted by GAO said the Corps could not have predicted the drought with enough certainty to warrant changes in reservoir decision.
GAO said some models were forecasting "wet conditions and others were forecasting dry conditions" leading up to the drought conditions. "As the drought took hold, experts who participated in our meeting said the Corps followed procedures as laid out in the master manual," GAO said.
The experts told GAO that in 2012 the Corps' water release for a full-service navigation season followed the master manual, "but it drained the reservoirs relatively quickly during the very dry summer of 2012," GAO said. "Specifically, according to the Corps report describing its management of the reservoir system in 2012, 22% of the water in storage was released in 2012, which would have reduced the amount of water available for future years if the drought lasted for several years."
In addition, GAO said experts agreed the Corps maintained appropriate "reservoir flexibility" in the winter of 2012-2013 when the Corps "kept winter releases higher than normal to ensure that water intakes along the river had continued access for municipal and industrial uses.
"Experts who participated in our meeting suggested that collecting more hydrologic data, improving existing hydrologic data, and incorporating probabilistic forecasting techniques could improve the Corps' ability to make release decisions in non-extreme events. The experts stated that these data and forecasts would not have predicted the 2011 flood. However, they explained that these data and forecasts could be helpful in future, less extreme, floods."
View the full GAO report here, http://tinyurl.com/…
View the lawsuit here, http://tinyurl.com/…
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