GRAND FORKS (AP) - Questions are being raised about the figures used by state officials in discussing the effectiveness of the outlet built to relieve Devils Lake flooding.

The Grand Forks Herald reported Sunday that documents from the North Dakota Water Commission indicate the outlet could be expected to take about 6 inches of water off the lake over 10 years, or less than 1 inch per year.

State officials have publicly said the outlet would take 1 inch to 4 inches of water a year off the lake, which has tripled in size after a series of wet years since the early 1990s.

The lower figures come from U.S. Geological Survey statistician Aldo Vecchia, the Herald said.

The outlet, which cost $28 million to build and $1 million annually to operate, pumps floodwaters into the Sheyenne River and ultimately the Red River, which flows north into Canada. Officials of Canada and Minnesota have opposed the outlet, worrying it will send potentially harmful material into their waterways. Downstream groups such as People to Save the Sheyenne also oppose it.

State Engineer Dale Frink said the estimate of 4 inches of water removed from the lake a year is what would result if the outlet pumps ran at full capacity for seven months. He acknowledged that such a scenario is inconceivable.