Farm Horizons, April 2013

New study shows tiling causes increased flow in MN rivers

By Jennifer Kotila

Just as commodity prices have ebbed and flowed over the years, so has the popularity of installing drainage tile in farm fields to increase their productivity. As the installation of drainage tile has ebbed and flowed, so has the debate over whether it is good or bad for Minnesota’s waters, and those downstream.

Although it can be argued that drainage is necessary to produce more food on less land to feed an ever-growing world population, the expansive network of ditches and tile used to drain water off the land in Minnesota for better crop production has unintentionally created increased river-channel erosion and sediment loading, according to a recently published study conducted by a team of researchers from the Science Museum of Minnesota and several major universities.

“Erosion of stream channels is a natural phenomenon,” explained Shawn Schottler, who led the study. “But our rivers are eroding at unnatural and increased rates, so we need to verify why this is happening. Our research concludes that agricultural drainage, more so than excess rainfall, caused the erosion of our river banks.”

The study compared changes in flow for 21 southern Minnesota rivers from 1940 to 2009, which showed flows in about half the rivers steadily increased in the last 70 years, with some nearly doubling; other watersheds showed no change in river flows. The conclusion was that changes in flow strongly correlated to changes in land use, including the installation of drainage tile and the types of crops being planted.

However, a major unknown factor is how much drainage tile is being installed in farm fields in Minnesota. The installation of drainage tile is a fairly unregulated endeavor, and it seems that nobody knows exactly how much, or where, tile is being installed. It is also unknown whether the installation of tile is replacing old drainage systems, or if it is a new system.

There are state and federal laws agricultural producers are supposed to follow when installing tile. However, if a producer is not planning to impact a certified wetland, there is very little oversight. The laws, enacted in the late 1980s and early 1990s, rely on the knowledge and actions of landowners to assure compliance with their requirements, according to the USDA.

At the federal level, agricultural producers are required to protect wetlands on farms owned and operated in order to be eligible for USDA farm program benefits. In order to assure compliance, producers should fill out a form at their local Farm Service Agency informing the USDA of their intentions.

At the state level, local government units regulate drainage activity, specifically soil and water conservation districts and watershed districts, which may also provide technical assistance to landowners. To assure compliance with state laws, producers should meet with SWCD or watershed district authorities, according to the USDA.

However, none of the agencies issue permits to producers for drainage tiling projects, or keep track of such projects. McLeod SWCD does not regulate the amount of tile that is installed in McLeod County, according to program director Ryan Freitag. “As far as how many miles of tile have been installed, it would be a complete guess and wouldn’t be correct,” Freitag said. “A landowner has made it known that he installed 700,000 feet of tile in 2012.”

The Buffalo Creek Watershed District, which has jurisdiction over agricultural land in McLeod County that drains into Buffalo Creek, does not permit for tile that is less than 8 inches in diameter, according to Corey Henke of the Buffalo Creek Watershed District. Although it seems a lot of drainage tile has been installed in the district, “We have not noticed an increase in flooding on Buffalo Creek,” Henke noted.

Wright SWCD also does not issue permits for tiling agricultural land, and relies on producers complying with federal laws regarding drainage, according to Kerry Saxton of Wright SWCD. It also does not keep track of the amount of drainage tile being installed.

Anecdotally, a lot of the drainage tile installed in the past was not effective, and producers decided to stop farming those areas, Saxton noted. Although drainage cannot be improved in such areas, it can be maintained. So some areas look like they have returned to wetlands, but with improvements in tiling and high commodity prices, producers are now installing better tile and again draining those areas, Saxton said.

The Minnesota Department of Natural Resources requires permits for numerous projects that affect Minnesota waters, but farmers do not need a DNR permit for tiling if the outlet does not include construction of an open ditch and is not intended to drain a public water or wetland.

About the only watershed district in Minnesota that tracks the amount of drainage tile being installed is the Bois de Sioux Watershed District, and it does so through a permitting process which has been in place since 1999, according to Al Kean, chief engineer at the Minnesota Board of Water and Soil Resources. Located in west central Minnesota, the watershed district includes the entire drainage basin, in Minnesota, of the Bois de Sioux River; counties include Traverse, Grant, Wilkin, Stevens, Big Stone, and Otter Tail.

“Their data indicates a rapid acceleration in pattern tiling in the BDSWD in recent years,” Kean said. “No other local government unit that I’m aware of has tracked tile installation in its jurisdiction, but we know high commodity prices in recent years have accelerated pattern tiling in much of Minnesota.”

Since the publication of the most recent study, Prinsco, a local tile manufacturer, has begun to compile information regarding tiling. “Our objective is to start addressing the educational pieces about drainage,” said Betty Bonnema of Prinsco. For instance, the company wants to educate customers and the public about what drainage is, how it works, and why it is needed to help people understand the big picture.

“There are environmental concerns in virtually all aspects of agriculture,” Bonnema said. “We want to be the solution to other issues, as well.”

“There is a real misconception about what motivates farmers to install drainage systems,” Bonnema added, noting that there will be 7 to 9 billion people in the world to feed by 2050, and tillable land is being lost at a rate of two acres per minute.

“The primary agricultural purposes of pattern tiling are to provide soil profile water conditions that enable better field access for planting and harvesting, and help avoid crop stunting or drown-out during the growing season due to excess soil profile or surface water,” noted Kean.

Tiling has been shown to pay for itself in a fairly short amount of time by increasing crop reliability and productivity in many soils in Minnesota that are typically too wet, he added.

Drainage has both positive and negative impacts, and research is ongoing. The University of Minnesota Extension Service has compiled a lot of information regarding agricultural drainage on “The Drainage Outlet,” an area of the U of M’s Extension website. More information can also be found on websites for the DNR, the US Fish and Wildlife Service, the Minnesota Board of Water and Soil Resources, the Red River Basin Decision Information Network, and the Minnesota Agricultural Water Resources Center.

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