An aggressive release schedule and warm weather has allowed the U.S. Army Corps of Engineers to increase flood control storage along the Missouri River reservoir system heading into the 2012 runoff season, officials said Friday.
“The total volume of water stored in the reservoir system is 56.3 million acre-feet,” said Jody Farhat, chief of the Missouri River Water Management Division, during a conference call with government and media representatives. “That is half a million acre-feet below the base’s annual flood control. That means, as of today, we have an additional half-million acre-feet of flood control storage available for the 2012 run-off season. Last year at this time, the system’s storage was at 56.9 million acre-feet, which is 100,000 acre-feet above the base of the flood control zone.”
According to a media release from the Corps, warmer than normal temperatures throughout the basin in the first half of January inhibited ice formation and allowed the rivers to flow freely, permitting for above-average runoff.
During January, runoff into the system above Sioux City, Iowa, amounted to .98 million acre-feet, which is 131 percent of normal.
In the middle of January, cold weather caused many rivers in the Missouri basin to freeze over, which reduced flows into the system.
Releases at Gavins Point were maintained at 22,000 cubic feet per second (cfs) in January, which is approximately 5,000 cfs above normal for the winter months. Corps officials plan to hold releases at that level through February unless ice-related concerns occur downstream.
“Both the Plains and mountain snowpack are below average for this time of year, and significantly lower than one year ago,” Farhat added. “But it’s still early in the snow accumulation season, and we’ll continue to remain vigilant in monitoring the situation.”
According to the Corps, 61 percent of the peak mountain snowpack accumulation has typically occurred by Feb. 1. Mountain snowpack above Fort Peck is currently below normal at 87 percent of average. In the reach between Fort Peck and Garrison, mountain snowpack is tracking at 96 percent of average.
Corps officials anticipate having a full navigation season this year. It begins in April and closes in November.
However, the March and May spring pulses have been canceled for 2012.
“This is due to a variety of factors, including the 2011 flood and its impacts on the existing infrastructure and ecosystem that are still being assessed, along with the ongoing review of the independent science advisory panel’s report on the Gavins Point spring pulse,” said Joel Knofczynski, the senior hydraulic engineer on the power production team of the Missouri River Basin Water Management office.
During the conference call, reporters from Missouri said their audiences are very focused on Gavins Point Dam.
One reporter questioned how much of the additional flood storage this year is at the last reservoir.
“I think their interest in Gavins Point may be misdirected,” Farhat said. “(Your audience) should be looking at the total system storage, because basically all the water that flows into Gavins Point flows right back out. It’s not a reservoir we use for flood control except when we get a rainfall event right downstream of the dam. We can shut off releases and store maybe a foot or two feet of water for a local flood event.
“Right now, that storage is available in (the Oahe Dam Reservoir),” she continued. “For the downstream folks, that is the best place to have it. Because when we have a downstream event, we shut back Gavins Point releases and then right up the line to Oahe. When we’re operating for flood control on the lower river, that water gets stored in Oahe. We’re anticipating that by March 1, we’ll have about 2 1/2 feet of additional storage in Oahe. That is what will provide the benefit for folks on the lower river.”
Another reporter asked whether it is practical to expand flood storage capacity at the Gavins Point reservoir, which is the smallest along the system.
“We haven’t looked at any options such as that,” Farhat said. “The volume of flood water that passed through the system this year was tremendous. It would take a very large increase in storage to make any appreciable difference.”
Col. Robert Ruch, the commander and district engineer of the Omaha District, said Gavins Point is not configured to handle more storage.
“There is no flexibility, really, to manage it differently to increase storage,” he said.