TMDL study–public money chasing the wrong solution?

Written by Jonathan Eisenthal

It may be frustrating, but seven years studying the southern reaches of Minnesota’s Mississippi River basin is just a start in understanding the workings of the river, including the level of cloudiness and the rate of sediment deposition.

However, Minnesota Pollution Control Agency has concluded its South Metro Total Maximum Daily Load Total Suspended Solids study, a study that covers the stretch of the river that includes Lake Pepin.

Similar TMDL studies covering the Greater Blue Earth River Basin and the Minnesota River Basin–tributaries whose waters ultimately flow into the Mississippi–have also been published. The PCA has opened public comment periods for all three studies–the 90-day comment period concludes May 29.

The studies will likely direct state projects that attempt to reduce turbidity (cloudiness) and sedimentation in Lake Pepin, among other water quality goals. These projects would be funded by the Legacy Amendment state sales tax revenue over the next decades.

Farm leaders had hoped for a more cooperative and comprehensive state about water quality challenges and potential solutions, and find instead that it focuses narrowly on agricultural contributions to the sediment load, excluding all other sources as seemingly insignificant.

Asked about where the TMDL study falls short, Steve Sodeman, a passionate agricultural water quality advocate, ticks off a list of items not included in the study: the increase in rainfall since the 1940s, the increase in groundwater consumption which generates wastewater entering the Mississippi, the outright dismissal of a notion that there is a background level of natural turbidity and sedimentation (in the past 11,000 years sedimentation and erosion have moved Lake Pepin from Saint Paul to its current location south of Red Wing), the increase in impermeable surface area in the seven-county metro and throughout the Basin, and finally the sheer size of the Mississippi River Basin, which drains more than two thirds of Minnesota’s land area.

Even with all three TMDL studies, significant portions of the Mississippi River basin have not yet been considered. The Mississippi River in effect drains everything in Minnesota, except for a line of counties along the Dakota border, which drain into the Red River of the North, and the northern tier of counties, which drain into either the Red River or Lake Superior. A few counties in the southwest corner of Minnesota drain into the Missouri River. 

Another significant blank spot is the role that increased precipitation plays.

“Since the 40s, average annual rainfall in the Basin has increased from 27 inches to 31 inches–that four inches is an incredible volume of water,” said Sodeman, who is a crop consultant in southern Minnesota. “When they talk about solutions, it makes me think of the CCR song ‘Who’ll Stop The Rain?'”

Water volume is at the heart of the issue because this volume increases the amount of energy in the river and serves as the main mechanism for putting sediment in the water–stream bank erosion.

Climate experts like Mark Seeley talk about a trend toward increased energy in rainfall events as part of an overall global climate change. Ten-inch flash floods, formerly considered to be once-in-500-year events, have occurred a number of times in the past decade, precipitating an incredible amount of stream bank erosion.

The PCA study focuses on the increased volume from farm tile system outlets to the exclusion of other sources of increased water volume.

Yet, PCA documents note that water consumption in the state of Minnesota has grown constantly and that about a fifth of that volume comes from groundwater. All that groundwater eventually ends up in the wastewater stream placed in the Mississippi by 14 Metropolitan Council operated treatment plants and a host of community wastewater treatment plants throughout the Basin. The Water Sustainability Framework Report (also funded by the Legacy Amendment) cites this startling figure: water consumption in Minnesota rose from 1,238 billion gallons in 1998 to 1,476 billion gallons in 2005–a 19 percent jump in seven years. Some 315 billion gallons in 2005 came from groundwater–in other words new water introduced into the river system when it entered the wastewater stream.

“It starts to feel political when this major source of increased water volume is ignored and the only source found to be significant is farm tile drainage systems,” said Sodeman.

University of Minnesota Soil Physicist Satish Gupta believes much of the dynamics of sediment transport remain poorly understood. He noted that more than 30 percent of the surface area in the seven county metro region is impermeable or semi-impermeable, and this figure represents dramatic growth since 1940. Despite holding ponds and other engineered features, it would appear to be reckless to claim that runoff from all this developed land does not contribute to increased stream bank erosion.

Sodeman said research has not yet provided a comprehensive picture of the way the river works and if it did, it might make for more realistic goals, he and other farmers feel. When it comes to halting sedimentation in Lake Pepin, he points to the case of a doctor who built his multimillion dollar home at the top of a bluff along the Minnesota River outside Mankato, and then spent another $350,000 to stabilize the stream bank–An incredible expenditure of wealth to assure that a piece of land several hundred feet between the bends of the river, would remain intact. Can Minnesota taxpayers support really make a dent by fighting a natural force that has been in operation in this region since the end of the last ice age? Spending on that scale along the length of the Minnesota is an impossibility, and Sodeman and others wonder whether it is in the end desirable to so forcefully counteract a natural process.

“There’s no debate when it comes to conservation–farmers are interested in keeping soil and nutrients on our land and out of our streams, lakes and rivers,” said John Mages, a farmer in Stearns County and president of Minnesota Corn Growers Association. “Our worry is that these goals, as worthy as they are, will be seen as a solution where they can’t possibly deliver that solution. Our hope is to head off false leads and find real world, practical solutions where possible, but also to accept conditions that are natural and not easily changed, to accept them for what they are.”

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