×

Missouri River Basin runoff increases again

Slight increase for Lake Sakakawea

What was already forecast to be the second-highest amount of runoff into the Missouri River system in 121 years has increased once again.

In their August forecast the U.S. Army Corps of Engineers has revised the amount of water expected to enter the Missouri River system this year to 52.9 million acre feet. That is an increase of three maf from the July 1 outlook. The reason, says the Corps, is that heavy rainfall over much of the basin in July was 7.0 maf. The long-term July average is 3.3 maf.

A statement issued by the Corps in regard to July rainfall reads: “Runoff remained particularly high in the reaches from Garrison Dam in North Dakota to Sioux City, Iowa, which ranged between three to seven times average.”

Runoff into the Missouri River system a year ago was 42.1 maf. Through July 31 of this year the amount reached 45.3 maf. While the majority of the increased runoff is below Lake Sakakawea, North Dakota’s largest body of water finished the month of July about one foot higher than original expectations. August should be similar.

The Corps’ July outlook projected an end of August elevation of 1,846.8 feet for Sakakawea. The August outlook shows an increase to 1,848 feet. By the end of December, says the Corps, Lake Sakakawea should drop to 1,839.5 feet and meet the end of February 2020 goal of 1,837.5 feet.

Lake Sakakawea remains the only one of the upper big three reservoirs that is within its prescribed “exclusive flood control” zone. Sakakawea stood at 1,851.24 feet Wednesday. The reservoir’s exclusive flood control zone is 1,850-1,854 feet, which is spillway level.

At the same time Fort Peck Reservoir in Montana was at 2,245.79 feet, a fraction below its exclusive flood control zone of 2,246-2,250 feet. Lake Oahe, below Lake Sakakawea, was at 1,616.90 feet Wednesday where the exclusive flood control zone is 1,617-1,620 feet.

Inflow Wednesday into Lake Sakakawea was listed at 40,000 cubic feet per second with discharge at 46,400 cfs, a release rate that is expected to continue through the end of this month. Fort Peck was releasing 14,800 cfs Wednesday and is projected to release at that rate until Sept. 1.

Newsletter

Today's breaking news and more in your inbox

I'm interested in (please check all that apply)
Are you a paying subscriber to the newspaper? *
   

Starting at $4.62/week.

Subscribe Today