Spring 2008

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Using watersheds to study the state of conservation

Catherine Kling points out that it takes a team of researchers to analyze watershed data, which is key to understanding Iowa’s water quality.

Every drop of water that falls in Iowa, not consumed by plants, animals or people, eventually flows through one of 13 watersheds and into the Missouri or Mississippi rivers. Watersheds overlap the state’s boundaries and lace across Iowa like giant puzzle pieces allowing water to flow from creeks to streams to rivers.

“Watersheds are what you have to talk about when you talk about water quality,” says Catherine Kling, professor of economics and division head of the Resource and Environment Policy Division at Iowa State University’s Center for Agriculture and Rural Development (CARD).

Kling and a team of researchers took on the task of assessing the “state of conservation” practices in Iowa. The Leopold Center for Sustainable Agriculture, Iowa Farm Bureau Federation, Iowa Soybean Association and the Iowa Corn Growers Association provided the funds to begin assessing the costs and benefits of conservation practices in Iowa.

“We’re thinking of costs in broad terms,” Kling says. “For example, to consider the full cost of changing the way you farm, you need to include the cost of adopting new practices as well as any lost profits. If you change the way you farm and you don’t make as much money, that is a cost and ideally those costs should be included.”

The researchers set out to answer three questions. What conservation practices are currently used in Iowa? What are the effects of those practices? And what would it take to improve water quality?

“It sounds easy but to do this well requires a great deal of data collection, modeling ability, computer work and knowledge of conservation practices. I am lucky to be able to work with a wide variety of folks at Iowa State who bring these talents together,” Kling says.

Cost of current conservation

The results indicate that Iowans invest about $435 million annually in agricultural conservation practices. The costs include $37 million for conservation structures, such as terraces and grassed waterways, and annual payments of $175 million to farmers in the Conservation Reserve Program, plus the cost of options like contour farming, strip cropping, no-till and mulch-till practices in farming operations. The research model did not include longer or more varied crop rotations, buffers, cover crops or the use of manure in place of fertilizer inputs.

Effects of conservation practices

Researchers used the Soil and Water Assessment Tool (SWAT) modeling tool to incorporate data on land use, soil, management practices and climate. The SWAT model is a compilation of 30 years of modeling efforts led by the U.S. Department of Agriculture Agricultural Research Service.

To analyze the effects of conservation practices in Iowa, researchers used the model to perform a hypothetical experiment, removing all existing conservation practices from the landscape and assessing how water quality would change. The results indicated that the seven primary conservation practices in Iowa eliminate from 11 to 38 percent of the total nitrogen, 6 to 28 percent of the nitrates and 25 to 58 percent of the phosphorus from Iowa’s watersheds.

Targeted suggestions improve water quality

Researchers looked at three potential water quality targets, which included the reduction of phosphorus by 40 percent, nitrates by 25 percent and the simultaneous reduction of phosphorus by 40 percent and nitrates by 25 percent.

Using these target levels the researchers used an evolutionary algorithm method, a new tool that can systematically analyze enormous data sets. The new tool can identify the combinations of conservation practices that can achieve the targeted goals at the lowest cost.

After 91 days of computer processing and over 116,000 SWAT model runs, there are no one-size-fits-all answers. The report states, “The effectiveness of a given conservation practice on a given field depends on the placement of other conservation practices and cropping systems in the watershed.”

“This type of modeling can really be helpful because it can provide the information about trade offs,” Kling says. “If you are worried about hypoxia in the Gulf of Mexico, that gives you one way to use your funds. If you are interested in improving Clear Lake, that may suggest another use of conservation funds.”

Research guides future conservation

Jeri Neal, who leads the Leopold Center’s ecological systems research initiative, said the research provides a benchmark of conservation practices and possible solutions for the future.

“We are impressed with these baseline numbers as an indicator of how much Iowans invest in conservation practices because clearly, Iowans care,” Neal says. “The models show we also can improve a lot more, but that it’s going to take a lot more dollars. From the Leopold Center's perspective, the model looks past single solutions toward a combination of practices that give us multiple benefits for our conservation dollars.”

Kling’s team of researchers was recognized for its work in water quality in February when they received the College of Agriculture and Life Sciences Team Award. Team members include: Hongli Feng Hennessy and Silvia Secchi, both associate scientists; Philip Gassman and Manoj Jha, both assistant scientists; and Todd Campbell, systems analyst. The team has been very successful in competiting for research funds, bringing in $1.5 million in competitive grants since 2003.

Kling says it takes a team of experts to understand hydrologic water quality modeling, economics and computing algorithms.

“All this stuff sounds very academic, but it is absolutely critical to have a knowledgeable team to answer these questions,” Kling says. “It’s really exciting to do research that people care about, that is grounded in academics and requires peer review because that input sometimes flags problems that you can’t see without that intensive final review.”

Kling serves on EPA Science Advisory Board

Cathy Kling has served on the U.S. Environmental Protection Agency Science Advisory Board since 1998. She currently serves as chair of the board’s environmental economics advisory committee. Members of the board are nominated by peers and EPA staff to serve. The board was established by Congress in 1978 to advise the EPA on technical matters. The board reviews the quality and relevance of scientific and technical information being used or proposed as the basis for EPA regulation. The board also reviews guidelines governing the use of scientific and technical information in regulatory decisions and critiques such analytic methods as mathematical modeling.