Gavins Point Dam

Water runs through the spillway at Gavins Point Dam in South Dakota.

Near-record runoff in the upper basin of the Missouri River last month means that releases from Gavins Point Dam will remain higher than usual into the foreseeable future.

The U.S. Army Corps of Engineers on Monday reported that last month’s runoff was the third-highest April amount in 121 years of records. A total of 7.8 million acre-feet of water, which is almost three times normal, poured into the upstream reservoirs.

The combined March and April runoff, at 18.7 million acre-feet, was the highest for those two months since record-keeping began in 1898. The previous record for the two months was set in 1952.

Runoff for the year is on pace to be the third-highest on record, according to the Corps, exceeded only by 2011 and 1997. But for now, last year’s runoff holds the third-place spot.

Discharges from Gavins Point, the farthest downstream of six massive dams on the Missouri River, are running at 55,000 cubic feet per second, not quite double the average for this time of year, which is about 30,000 cfs.

John Remus, chief of the Corps’ Missouri River Basin Water Management Division, said the high discharges from Gavins Point are needed because two of the upstream lakes are near their capacity for flood storage.

Mountain snowpack has peaked near average and has begun melting, according to the Corps.

Not only is a lot of water coming out of the dams, but significant runoff is pouring into the Missouri River from tributaries that dump into the river downstream of Gavins Point. April runoff between Gavins Point and Sioux City, Iowa, was the second-highest on record.

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