Studying the Ties Between Climate, Agriculture, and Groundwater Quality

July 21, 2016, 6:45 a.m. ·

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Many studies looking at the future of a changing climate have focused on impacts to water quantity—less snowpack in the mountains, more heat and drought. But a team from the University of Nebraska-Lincoln is studying what climate change might mean for water quality in Nebraska and other Great Plains states.

Climate change projections for Nebraska include warmer temperatures, more severe weather, and decreased soil moisture—all of which will impact agriculture. Shannon Bartelt-Hunt, UNL associate professor of civil engineering, is studying the connection between agriculture, climate and groundwater quality under a nearly $600,000 federal research grant jointly administered by the U.S. Department of Agriculture and the National Science Foundation.

“We're looking at how climate might directly impact the fate of groundwater contaminants, and also how climate-induced land use changes could affect groundwater quality,” Bartelt-Hunt said. The team is working under the assumption that increased drought and water shortages in the southern plains states (like Oklahoma and Texas) will drive corn and cattle production to further concentrate in states higher north, like Nebraska, that have more stable groundwater resources.

“But then the question is when you have more animals and more production going on at the land surface, what kind of implications does that have for groundwater quality?” Bartelt-Hunt said.

To answer that question, the team is studying three different trace organic compounds commonly applied to fields or given to animals in feedlots:

  • Atrazine, a widely-used pesticide
    • Estrone, a steriod hormone
      • Sulfamethazine, an antibiotic
      • Bartelt-Hunt says those chemicals, which currently are not regulated, can have health impacts on humans and animals. Overuse of antibiotics can lead to antibiotic-resistant pathogens or bacteria. Research has shown steroid hormones can lead to damaging reproductive impacts on aquatic species.

        Atrazine is applied directly to fields. The other two compounds are released in animal manure. Feedlots are subject to water regulations, but oftentimes the manure from those feedlots is spread on cropland as a fertilizer, says Bartelt-Hunt, “which is a great thing, but those compounds can then leach out of that manure when it rains and then either be carried into surface water or infiltrate down toward groundwater.”

        That matters because Nebraskans rely on groundwater for most of their drinking water and irrigation water supply.

        The research team is using a detailed set of water quality data gathered in the early 1990s in central Nebraska near the Platte River, which tracked fertilizer use, irrigation and nitrate concentrations. Bartelt-Hunt says the study area has a shallow groundwater table and sandy soil, which means it responds more quickly to changes.

UNL Research Team:

Shannon Bartelt-Hunt, associate professor of civil engineering.

Eric Thompson, associate professor of economics and director of the UNL Bureau of Business Research.

Simin Akbariyeh, PHD student working on the groundwater simulations.

“We felt like it was a worst-case scenario,” she said, “If we see impacts to groundwater they're going to happen quickly at that site” as opposed to places with longer response times where it can be hard to find results in the data. During the last year, the team used that central Platte data to validate their groundwater computer model.

UNL Economics Professor Eric Thompson says the area of central Nebraska they’re studying is good for other reasons, too.

“It's an area where crop, particularly corn production, beef production and ethanol production are concentrated. So this allows us to look at the interaction of those three sectors and see how that affects land use and ultimately groundwater quality,” Thompson said.

He’s been working on economic models to study the human response to climate change in the farming and ranching sectors. The team will combine those with the groundwater model to understand the bigger-picture climate impacts to water quality based on changing land use.

“So they'll be direct effects on cattle on feed numbers and on crop production, and they'll also be indirect effects: growth of cattle on feed could also affect the need for crop production and vice-versa,” Thompson said. He says combining human behavior with scientific understanding of natural processes can lead to greater insights.

“One interesting question is whether the effects of human behavior are of a similar or perhaps even larger magnitude than the direct effects of climate change on the properties of the soil,” Thompson said.

When completed, the project will provide detailed findings on one particular site in central Nebraska. While Bartelt-Hunt acknowledges the results of this study will be limited to that area, she thinks the research approach could be applied to other locations in the future.

“One of our challenges is then going to be trying to determine how that information might translate into a wider realm,” she said.

Thompson says these findings will be useful to many people in the agricultural sector and other related sectors, who “need to know how vulnerable the economy is to potential climate change.”

The team is about halfway through the project.

NET News and Harvest Public Media are collaborating on a water quality reporting project. Stay tuned for more radio stories and a public television documentary this fall.