Thousands of river miles run throughout Iowa, a state bordered by the Missouri River on the western rim and the Mississippi River on its eastern side.  Iowa cities and towns encompass a state defined by its waterways.

Chris Jones, Water Quality Research Engineer, University of Iowa: A watershed is an area of land that drains to a common point.

Two very different watersheds in Iowa, the Raccoon River and the Upper Iowa, are a perfect example of our state’s unique characteristics.

Chris Jones: Well the Raccoon River is really three rivers. The North Raccoon, the middle Raccoon, and the South Raccoon. The North Raccoon being the biggest. Confluence of the three is just west of Des Moines near Van Meter, Iowa. 

In west central Iowa, a sprawling combination of rural counties and the state’s largest urban center, Des Moines, collectively make up the North Raccoon River Watershed. In this watershed, more than 80 percent of the land is held for row crop production with a rotation of corn and soybeans.  The land is tiled, a process of creating an artificial water control system under the soil. Its similar to gutters on a home sending water away from the land and preventing corn and soybeans in otherwise marshy areas to maintain optimal moisture levels.  

Chris Jones: A lot of the ground there in the Raccoon watershed is very suitable for cultivation of corn and soybeans. We have a lot of drainage tile in that watershed and so along with the fact that we have a fair amount of livestock production especially in the northern part of the watershed. That all figures into the stream having a high nitrate level. Then probably the most special part of it is it’s a major source of drinking water supply. 

Agricultural tile is prominent at the northernmost “headwaters” of the Raccoon River.  Here in Buena Vista county near Marathon, Iowa, a collection of metal pipes run water into a channel. These pipes begin the North Raccoon River’s long journey past Storm Lake, farm fields, countless communities, and inevitably to downtown Des Moines where nitrates in drinking water are filtered out at the Des Moines Water Works.

Chris Jones: So the Raccoon probably has the highest nitrate concentration of any stream of its size in North America. Drainage tile is the primary delivery mechanism from nitrate to the stream network.

The Raccoon River watershed contrasts with that of the Upper Iowa River watershed in northeast Iowa.  The Upper Iowa winds through miles of high limestone bluffs.  While its headwaters are in Minnesota, it eventually empties into the Mississippi River. Along the way, the Upper Iowa runs through varied karst topography and the nearby towns of Decorah.  Karst topography is known for its easily dissolved bedrock like limestone. Its existence in this region lessens the amount of available topsoil and limits how much land may be used for crop production. 

Chris Jones: The Upper Iowa is draining what we call the paleozoic plateau and we’ve never really had glaciers in that part of Iowa. We have a thin layer of topsoil there and drainage tile like we have in central Iowa is really much less necessary up there. The water percolates through the soil profile and gets to bedrock much more quickly in the Upper Iowa River watershed. Also the materials in the river bed there tend to be rockier and sandier than say the Raccoon where we’re going to have more silt and clay material. So all these things factor into water quality.

While the Upper Iowa nitrate loads are less than commonly found in the Raccoon River, this northeast Iowa watershed still confronts water quality concerns.

Across Iowa’s 99 counties, multiple watershed approaches and specific watershed plans are utilized to confront water quality concerns such as high nitrate levels based on sound science, as well as regulatory and voluntary initiatives that attempt to engage stakeholders to achieve an ultimate goal: safer and cleaner water.

Back in central Iowa, efforts to reduce nitrate loads are part of a watershed approach designed to increase nitrate monitoring data with real-time sensors paired with state and federal funding to modernize drainage tile and add buffer strips to absorb nutrients. To date, current efforts have not substantially altered a long-term trend of higher nitrates in the Raccoon River watershed.

Chris Jones: If you look at the money we’re investing through cost share programs it’s a tiny, tiny fraction of what we need. So how much do we want to solve this is the basic question. You know that money has got to compete with all these other things that we want, roads and schools and so forth. So as a society do we want to solve this or not, I think that is the basic question here that we don’t know what the answer is. Geology, the weather, all of these things does not conform to political boundaries, but it does conform to these natural boundaries like a watershed boundary. So that is why its important that we manage our water resources on the watershed scale and not so much on the state scale.

Watersheds and water quality impact every corner of Iowa.  The potential solutions confronting land use, urban use, and voluntary versus regulatory measures will likely determine the watershed approach in the 21st century and Iowa’s water quality for decades to come.

REAP
Gilchrist Foundation