What a year it has been! A snowless winter led to worries about drought— but then the rain came. And came. And came.

For several weeks, streams and rivers across Minnesota were at flood levels. Several stream gauge stations recorded new high flows. Weather watchers in some areas reported several months of normal rain falling in just a few days.

As usual, tile drainage became a hot topic. It seems whenever stream levels rise, so do the calls critical of tiling. I have written several stories in the past about tile drainage as a conservation practice, reducing surface runoff, allowing for crop growth and creating storage space for the next rain.

I recently came across an agricultural magazine article published in July 1997. Many will remember the widespread flooding that occurred earlier that year. The article noted that accusations by the Sierra Club that field drainage tiles are a culprit contributing to those spring floods “made sense to many.”

The article then drew on expertise from researchers at Mankato State University and the University of Minnesota to explain how drain tile really works. Henry Quade, a biology professor and then-head of the MSU Water Resources Center, concluded that the overwhelming reason for flooding is precipitation. Research at MSU showed that agricultural drainage has a minimal effect on flooding and may often limit its severity.

The Sierra Club based its views on tile drainage on reported wetland loss, concluding that about 150 days of floodwater could have been absorbed by lost wetlands. To many, this makes sense if one ignores the potential for water to be stored in the soil and meted out slowly by tile engineered to do just that.

Science-based philosophy

Gyles Randall, a highly regarded researcher at the University of Minnesota’s Southern Experiment Station in Waseca, described the Sierra Club report as representing “a philosophy and attitude that’s not science-based.”

David Mulla of the University of Minnesota noted that catastrophic flooding is cyclical and occurred long before drainage or human development was a factor. Quade, Randall and Mulla agreed that it appears drainage tile often keeps the crest of a flood lower than would occur naturally.

Randall, who led tile drainage research efforts in southern Minnesota for decades, concluded that “It’s a fair generalization to say that tile keeps peaks down.”

Currently the Board of Water and Soil Resources regulates agricultural drainage in Minnesota as authorized in the Wetland Conservation Act. Opponents of tile drainage continue to push for more restrictions on water management projects. Drawing from the research base can help ensure that science is considered and incorporated into the process.

Formo is executive director of the Minnesota Agricultural Water Resource Center.