Mountain runoff declines

Mountain snowpack is producing less runoff than anticipated in the upper reaches of the Missouri River reservoir system, but record flooding is occurring at several downstream locations.

Those were the main points stressed on a conference call conducted by the U.S. Army Corps of Engineers Friday.

Jody Farhat, Omaha, Neb., Corps’ chief of water management for the Missouri River Basin, said that a lot has changed within the system in the past 10 days. Farhat stated that, “for some reason snowpack melt is turning out to be far less than originally forecast.”

It is possible that diminished runoff will lead to a revision of the Corps’ earlier projections for Lake Sakakawea. A new Sakakawea outlook is expected the first week of July. The June outlook called for a maximum summer elevation of slightly over 1,846 for Sakakawea at the end of July. Current projections show Sakakawea should end this month at 1,844.8 feet.

Recent heavy rainfall at various locations below the Upper Missouri Reservoirs has led to record flooding along the Missouri River. Steve Predmore, National Weather Service, said flooding at some Iowa locations reached three feet above crest records set in 1993. Predmore noted there was minor to moderate flooding at several locations in the lower Missouri River Basin, a threat that he termed “typical” for the lower third of the basin throughout the summer.

“There are no other locations on the Missouri River expected to reach flood stage,” said Predmore after noting expected crests in Nebraska and Missouri.

Releases from Gavins Point and Fort Randall, the two southern-most reservoir on the Missouri River system, had earlier been reduced to help alleviate downstream flooding. However, said Farhat, as the flood threat recedes outflows will be increased.

“Gavins Point went from 30,000 cfs to 10,000. Fort Randall was cut dramatically, from 22,000 cfs to 2,000,” said Farhat. “We’ll increase releases from Fort Randall Saturday and noon Monday for Gavins Point.”

Farhat explained that both the Gavins Point and Fort Randall reservoirs had risen while outflows were curtailed but, barring additional rainfall, would soon return to more normal operating levels. Furthermore, said Farhat, “only 16 percent of the flood control zone” of the three upper Missouri River reservoirs, including Lake Sakakawea, was currently in use. The implication was that there was room to store additional water if it would become necessary to reduce flows downstream due to another session of flooding.