Severe flooding is considered unlikely
By Tim Leeds
The Milk River irrigation system is as full as it has been in years, and there is a chance weekend rains could cause some flooding but not much of a chance.
"It would take another 2 or 3 inches, which is not that severe a storm," Scott Guenthner, hydrologist for the federal Bureau of Reclamation said Thursday. "The extent is more than how much. If it fell over a large area upstream, it could be a problem."
The National Weather Service predicts rain and thundershowers over the weekend, but not enough to cause severe flooding.
Rain and snow that fell from June 7 through June 12 swelled the Milk River, filling Fresno Reservoir for the first time since 1997. A dam on Sage Creek overflowed after more than 7 inches of precipitation fell in the Sweet Grass Hills, but much of the runoff filled ponds and reservoirs and never reached Fresno.
Other areas of the state experienced flooding, but outside of some road and bridge damage and basement and street flooding, most of the Havre area escaped severe damage.
Guenthner said a half-inch to an inch of rain probably wouldn't cause severe flooding, although the Milk will probably overflow its banks in some areas.
"Some low-end flooding is unavoidable," he said. "From the information we're getting, (the river) is getting high and we're recommending people move their pumps up higher."
The bureau is controlling outflow from Fresno to reduce the chance of flooding, he added.
Jason Anderson, meteorologist with the Weather Service in Great Falls, said the Havre area will probably get some rain, but less than 2 to 3 inches. But it's impossible to predict exactly how much will fall, especially with the variable amounts thunderstorms can drop, he added.
"It depends on if you're at the right spot at the right time," he said. "In the Havre area it doesn't look like you have a chance of getting a lot."
Further south and east, from the Lewistown area on, there is a better chance for heavy showers and thundershowers, Anderson said.
It's also difficult to predict the effect of rain on the Milk east of Fresno, Guenthner said.
If large amounts of rain swell tributaries of the Milk like Lodge Creek and Battle Creek, which flow out of Canada, flooding could occur in areas downstream, like Malta, Anderson said.
Guenthner said Fresno can still be used for flood control if precipitation upstream sends more water into the reservoir.
"We could control it some," he said. "There's still a lot of capacity at Fresno."
The water level is about a foot above the storage level of the dam, which is about 2,575 feet, and water is flowing over the spillway for the first time in five years.
The level is about 17 feet below flood level. Guenthner expects the level of the reservoir to continue to drop slightly even if a half-inch of rain falls.
The level of Fresno peaked Wednesday at 2,576.62 feet, with storage of 101,112 acre-feet of water, or more than 4.4 billion gallons. The level dropped .05 feet Thursday, with storage of 100,847 acre-feet.
The bureau has been regulating outflow from the reservoir by adjusting its release gates, Guenthner said. The bureau has no control over how much water flows over the spillway.
The bureau has been adjusting the gate to keep the outflow at about 1,300 cubic feet per second. Guenthner said the level has been kept that high to lower the reservoir and increase available storage capacity.