The first Iowa settlers found a landscape that looked very different from what we know today. Where we see acres of corn, soybeans and pasture, our ancestors saw prairie and wetlands. Stewart Melvin, professor emeritus in the agricultural and biosystems engineering department at Iowa State University, has spent the last 35 years studying the impact of engineering and management practices on the quality of surface and subsurface water in agricultural watersheds.
Melvin talked about the history of drainage in Iowa at a recent research forum. "The Swampland Act of 1850 turned the swamplands no one wanted into public land," he said. "Then Congress gave 65 million acres to 15 states for reclamation and to eliminate what they called 'mosquito-breeding swamps.' Thus began decades of work encouraged by federal and state governments to install drainage systems on millions of acres of land."
A 1903 survey by personnel in the Department of Soils at what was then called Iowa State College showed that four million acres in Iowa had low yields because of poor drainage. That translated into an estimated loss of $20 million in state revenues.
The Iowa Legislature finalized a drainage district law in 1906. It allowed landowners to form legal drainage districts to obtain a common outlet, especially in the prairie pothole area of north-central Iowa. Once brought into production, this land was highly productive and a good investment.
Fast forward to 1970, when some people began to talk about the quality of water coming out of drainage tiles. A research project was established on ISU land near Ames to determine nitrate losses from drained lands. And one of the first watershed studies in the United States got underway at Four Mile Creek in Tama County.
In 1978, 36 one-acre plots with a drain line in the middle and border tiles on the edges were established on ISU's Northeast Iowa Research and Demonstration Farm near Nashua. Since then, researchers have been looking at how agricultural production practices impact the quality of drainage water, including such things as tillage and fertilizer, manure and herbicide applications.
Melvin said researchers are now turning their attention to delaying or reducing subsurface drainage with the use of both infield and downstream practices. Constructing wetlands to treat drainage water is one option. Installing control valves into a drainage outlet can help manage the water table in the field. Another option is placing a biofilter in the tile line. All these techniques slow the water flow, increasing yields while decreasing the loss of nutrients and pollutants.
"Drainage has played a key role in the development of Iowa and its productive agricultural lands," he said. "Significant research has been done and is being planned to maximize the benefits and minimize the drawbacks of subsurface drainage."