Constructed wetlands like this one could help to reduce nitrates in drinking water supplies. (Photo courtesy of The Nature Conservancy)
By Carrie Muehling
BLOOMINGTON – Conservation practices could improve the drinking water supply in Bloomington.
The City of Bloomington began working with The Nature Conservancy and the Environmental Defense Fund more than a year ago to address the concentration of nitrates in the drinking water supply. One option is installing extra filtration capacity for nitrates, which would be a costly project. Conservation practices could provide an alternative.
"What we're doing is looking at an alternative to putting in an expensive treatment facility by treating the watershed, and in this case we're looking at putting in constructed wetlands back onto the landscape that historically were there in some capacity to retain some of that runoff from agricultural fields," said Maria Lemke, aquatic ecologist for The Nature Conservancy. "In this case, if they can retain that water long enough to have the concentrations of nitrates be reduced so that the water running into the waterways - into Money Creek and Six Mile Creek - those nitrogen concentrations are lower than they would be without the constructed wetlands."
The nitrogen concentration in Lake Bloomington and Evergreen Lake likely comes from agricultural production practices.
"Previous research from Illinois State University has shown that agriculture is the leading source of a lot of that nitrate, which makes sense because that is the dominant land use within the watershed leading into those reservoirs. But we also think there is an enormous amount of potential for farmers, through voluntary conservation practices, to be part of the solution to this particular issue," said Dr. Jeff Walk, director of science with the Illinois Chapter of The Nature Conservancy.
Walk wants to see the maximum conservation benefit in terms of improvement in water quality, with minimum effect on operation of landowners and farmers. That means small amounts or no additional land taken out of ag production, providing good economic incentives, and having no effect on productivity or drainage on the rest of the farm. It means giving farmers the ability to use fertilizer and tile drainage to maintain the productivity of Illinois farmland. Over time, farmers have been steadily using less fertilizer but Walk says it will take some additional strategies.
One of those strategies is placing wetlands in specific locations in the watersheds where they'll be most effective. These very large watersheds measure 25,000 acres and 45,000 acres in area. The group is working with the University of Illinois and Illinois State University to map out the watersheds and figure out how and where they drain and where the wetlands would be most beneficial.
"We're really focused on the water that drains off these agricultural lands through underground tile systems. There is a lot of surface water that runs off these fields, too, and that's really been addressed by a lot of other conservation practices that have been installed in the watersheds. But there haven't been any practices installed that address this tile drainage, which runs underneath the ground and underneath all those surface water practices and then this way the water basically runs off the field unimpeded directly into the creek. That's why we're focused on constructed wetlands. We want to intercept that tile water and run it into a wetlands system first and then run it back out of the wetlands system and back into the creek so it's treated before it enters into the system,” said Lemke.
They are also working closely with universities to understand where the tiles are, using GIS data, aerial infrared data and other technology to get a detailed topography of the landscape. Also involved are the Natural Resources Conservation Service (NRCS), Farm Service Agency (FSA) and Soil and Water Conservation District (SWCD) to conduct outreach to landowners and walk them through the paperwork to get enrolled in appropriate farm programs. The Illinois Department of Natural Resources (IDNR) also has some incentive programs for landowners. There is a great deal of collaboration between state agencies and private conservation organizations.
The voluntary program is available through USDA's Farmable Wetlands Program, a provision of the 2008 Farm Bill.
"So these nutrient treatment wetlands that we've seen put in the Mackinaw River by The Nature Conservancy, and that the City of Bloomington is starting to put in - that's a great example of a practice that can be cost shared under EQIP. That's a very important program for farmers in Illinois and throughout the country," said Sean McMahon, North American agriculture program director for The Nature Conservancy.
McMahon is concerned about the expiration of the current farm bill. He is among many in the agriculture community who are hoping Congress will pass a five-year farm bill so farmers can have certainty to plan moving forward. He said a one-year extension would leave less money available for the conservation programs already discussed. Many people may not realize the conservation title of the farm bill could affect their drinking water supply. The conservation title only accounts for about seven percent of the farm bill, compared to the 70 percent for the nutrition title, which includes food stamps and other assistance programs.
"That seven percent is very important for water supply, for preventing soil erosion, and for helping to make our farms more resilient so that they are able to really weather the seasonal climate variability that we're seeing this year with this very intense drought," said McMahon.
Lemke said one thing that makes this project different from other similar ventures is the emphasis placed on monitoring.
"A lot of times we put in a lot of practices and we think they work and we don't know how well they work. So one of the things we're doing with this project is monitoring how well these wetlands work,” explained Lemke. “So, doing the science and the research is going to give us the ability to understand what kind of reductions we can expect to see from these wetlands in the watershed, so at some point we can look at how far will these wetlands get you in terms of nitrate reduction, and that all comes back from all of the scientific monitoring of how well these wetlands work."
A cost benefit analysis of watershed conservation versus expensive water treatment plant will help to measure the efficiency of the system.
"So it's kind of this gray versus green economic analysis, which is extremely important when you look at the long term conservation of these watersheds,” Lemke said.
The goal is to make the system self sustaining. Funding is available from a federal NRCS program grant that will help fund the project over the next three years. At that time, the groups hope to provide a "conservation blueprint" that can be useful for projects in other areas, as well.
"I really applaud the City of Bloomington for their forward thinking and how they're approaching the issue of their sources of drinking water. They identified that subsurface nutrients or the water quality from subsurface tiles was their number one water quality concern. So they're putting in these nutrient treatment wetlands that intercept the tile lines and provide clean water to the city, and they've found that they can do that at about one third of the expense of what it would cost to put in a water treatment facility and maintain that facility,” said McMahon.
Preliminary economic analysis shows these constructed wetlands can sequester and remove nitrates from tile drainage water for roughly one third of what it would cost the city of Bloomington to install a reverse osmosis treatment plant to remove the nitrates. The project has already begun and six or more wetlands will be constructed over the next three years.
Carrie Muehling can be reached at firstname.lastname@example.org.