By Michael Avok
OMAHA, Neb (Reuters) - For people fighting Missouri River floodwaters for weeks now from Montana through South Dakota, the fear of rainstorms that could pressure already strained levees were the biggest concern on Wednesday.
Federal officials have planned to slowly reduce releases from four Missouri River dams over the next several weeks while leaving them at very high levels, but have little room yet in swollen reservoirs to cope with additional heavy rains.
Forecasts were favorable over the next several days in the northern Missouri River basin and the nearby Souris River Basin, where Minot residents battled flooding that forced evacuation of a quarter of the city, North Dakota's fourth largest.
Massive water releases from rain and snow-melt swollen reservoirs in Canada in turn forced U.S. officials to release water from Lake Darling Dam above Minot at rates triple the capability of the city's defenses, overwhelmed a week ago.
The U.S. Army Corps of Engineers is reducing water releases from Lake Darling Dam gradually, but it may take two or three weeks before the Souris River is back in its original channel, Lieutenant Colonel Kendall Bergmann said on Wednesday.
That outlook is based on "a perfect world with no rain," Bergmann said in a telephone interview.
A deep melting snow pack and widespread heavy rains have been blamed for forcing record water releases from the six Missouri River dams from Montana through South Dakota.
In South Dakota, dry weather is expected over next couple of days, but the biggest concern is, "That there will be more rain in the Missouri River Basin that will put pressure on the Corps to increase river levels," Pierre Mayor Laurie Gill told Reuters in an emailed response to questions Wednesday.
Levees have been holding, though some neighborhoods in the city and Fort Pierre nearby have flooded houses, Gill said.
A storm system is expected to produce a low chance of showers and storms Saturday night and Sunday in central South Dakota, said Mike Connelly, a National Weather Service meteorologist based in Aberdeen, South Dakota.
"There is more just a general risk of an isolated storm or two for next week, but no systems that are expected to produce widespread heavy rain like we had earlier in June," he said.
In the Missouri and Souris River regions of North Dakota, thunderstorms could bring 1 to 3 inches of rain Thursday night in some spots, but not enough to affect river levels, weather service meteorologist Todd Hamilton said.
There is a chance for storms through midweek next week, but "any rain that we do have, these systems are going to be transient in nature, moving through," Hamilton said.
The Corps water release plan through July 22 calls for gradual reductions at the four northernmost Missouri River dams in Montana, North Dakota and South Dakota. At the southernmost dam, Gavins Point, releases are scheduled to stay at peak.
The Missouri River runs freely from Gavins Point for more than 800 miles to the Mississippi River near St. Louis, making the maximum releases there a focus for residents downstream.
Water has pressed through or over levees in numerous places from Iowa through Missouri in the last several weeks, forcing evacuation of several smaller communities.
Flooding also has closed numerous roads and bridges and waters have surrounded, but not inundated, the Fort Calhoun Nuclear Power station north of Omaha, Nebraska.
(Additional reporting by David Bailey in Minneapolis; Editing by Jerry Norton)