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Iowa Works to Reduce Gulf of Mexico Dead Zone

posted on September 17, 2009 at 9:19 AM


Next week, September 21st, 2009, in Des Moines, a national Environmental Protection Agency task force convenes to examine how to reduce pollution entering the Mississippi River. That pollution, scientists say, comes from fertilizer runoff from farm fields in Iowa and other Midwest states.

While the problem is far from "solved", Iowa has worked to reduce the runoff.

This wetland looks typical enough with its wildlife habitat and tall prairie plantings.  But what is atypical is the surrounding equipment used, which automatically takes water samples every six hours. The samples taken will be analyzed to measure the amount of nitrates, primarily from farm fertilizer, running off the land into the wetland ... and the amount being discharged after it is filtered by the wetland.

This part of a Conservation Reserve Enhancement Program – or "CREP" wetlands.  The wetlands are strategically placed in the bottomlands of a watershed to help filter out nitrates not just from one farm, but from land above it in the same watershed.

Shawn Richmond, CREP Program Coordinator, Iowa Dept. of Agriculture and Land Stewardship: "The wetlands are specifically targeted for nitrogen reduction goals. CREP really isn't a walk-in sign-up type of program where most people are going to qualify because there are a lot of criteria."

Shawn Richmond says topographic analysis determines best placement of CREP wetlands. Since 2001, 35 CREP wetlands have been constructed in north central Iowa -- where farmland is heavily tiled for drainage to create better land for growing crops.

Iowa State University is monitoring the water quality, measuring current levels of nitrate removal and projecting out long-term, the potential for cleaning up the water.

Bill Crumpton,  Ecology, Evolution and Organismal Biology, Iowa State University

"We monitored about a third of those sites. The long term estimates of the removal by those 27 wetlands is that they would've removed about 52 percent of the nitrate that entered them."

If we wanted to remove more then you'd make the wetlands a larger percentage. If the wetlands were occupying a half percent of the landscape you want to remove more you have them occupy 1 percent so instead of a 5 acre wetland at the bottom of a thousand acre drainage."

The wetlands do take up a lot of land, making decisions difficult for some landowners. Farmer Jim McHugh has two CREP wetlands on his property near Boone. He says it took him a year to decide whether to give up some of his pasture ground for one of the CREP projects.

Jim McHugh, Boone farmer "We need more conservation. You can see the ground very, very rolling around me and most of its in row crop. So this is an excellent settlement basin for any run-off that we might have coming off the hills."

McHugh says he also enjoys the waterfowl attracted to his wetlands -- including a number of Trumpeter swans.

But not every farmer can pencil out the benefits of wetland over production agriculture.  That's one reason the Iowa Soybean Association is testing a smaller treatment system, called a bio-reactor.

Keegan Kult, Watershed Management Specialist, Iowa Soybean Assoc.  "We cut into an existing field tile and divert water through an underground trench of wood chips. The trench needs to be full of the carbon source so we choose woodchips because of the availability of them."

Essentially, it’s a microbial process used to break down nitrate in the water.  The nitrate is converted to gas and expelled.  The treated water then exits by way of another tile line in the trench and enters a nearby creek.

This process is fairly new to Iowa, but similar bioreactor projects in other states have not been without problems. There have some concerns with an unintended byproduct, methyl mercury.

Keegan Kult, Iowa Soybean Association: "The big thing with that is if there is a background source of mercury which Iowa hasn't been known to have a high source of mercury like perhaps Illinois and perhaps Minnesota.  Also, we know now to control the, the flow of the water fast enough so we're not getting the full reduction of nitrate. We want to leave a couple parts per million nitrogen left in the water actually because then we're not going to see that sulfate reduction and hopefully then we avoid the methylation of mercury."   

There may be science behind both the use of bioreactors and wetlands to help solve the hypoxia issue of sending too much nitrogen from fields to the Mississippi River and Gulf of Mexico.  But one thing proponents of both systems agree -- their projects don't address a federal task force goal to also reduce phosphorus pollution.  And neither can meet the task force goal to reduce nitrate 45 percent reduction by the year 2015.

Todd Sutphin, State Watershed Coordinator, Iowa Soybean Association. "It will be challenging you know its going to take a multitude of practices. I know that we talked about wetlands, we talked about the bioreactors, the field management, the buffer strips. It's going to take all those to get down to that number. Achieving that number won't happen overnight either."

Shawn Richmond, CREP Program Coordinator, IDALS: "With the CREP program today, we develop about 15 to 20 sites a year at best. On that frame of things we estimate it would take 325 years at that deployment rate to be able to put enough of these on the landscape to have enough effect to meet the goal for 45% reduction in nitrogen in just, for Iowa's share of the goal, the hypoxia goal."  

Tags: agriculture Gulf of Mexico Iowa pollution water water quality wetlands