It will cost $0.7 to 12 million over 20 years to address the increased risk of nitrate contamination of private wells in south-eastern Minnesota, Bonnie Keeler and Stephen Polasky from the University of Minnesota estimated, by using integrated biophysical models and economic valuation.

“It is a difficult situation because the communities in south-eastern Minnesota rely financially on the crops that are grown there, but we wanted to highlight the hidden costs of this growing industry,” Keeler told environmentalresearchweb. “Our study shows that these communities need to think about the consequences of land-use change and how it can have negative financial and health impacts on the people living in the area.”

Many of the wells in the area are not tested for nitrates, but when they are tested and found to be above the US Environmental Protection Agency maximum contaminant level of 10 ppm nitrate-nitrogen, the householders have several options. Keeler and Polasky found that a significant number (36%) choose to do nothing. Those that do decide to take action can either install equipment to treat the water, dig a new well or buy bottled water.

“All of these actions mean that these households will incur considerable costs,” said Keeler. “The real costs are likely to be even higher when you factor in health implications, reduced property value, treatment of livestock and litigation. Our study did not look at these indirect costs, so while our estimates represent a large amount of money, they are likely to be underestimates.”

Keeler and Polasky gathered data from 11 counties in south-eastern Minnesota and looked at different factors that could lead to well contamination. These included soil characteristics, local geology, the depth of the well and the land use around the well. They then extrapolated these data to wells where data were missing and calculated the likelihood of those wells being contaminated. This meant the researchers were able to calculate the costs of dealing with contamination in all contaminated wells in south-eastern Minnesota. “While the costs associated with groundwater contamination may be burdensome to households, the total costs of nitrate pollution are unlikely to exceed the value of crop production associated with agricultural expansion,” said Keeler. “We hope our approach can serve as a template for future interdisciplinary work where data are needed to inform cost-benefit assessments, design water trading programmes, or to target lands for investments in water-quality protection.”

Keeler and Polasky reported their study in Environmental Research Letters (ERL).

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