Warm winter conditions tied to human-caused climate change can make nitrate pollution reach drinking-water supplies more often, according to experts and officials cited by the Associated Press in a report on the problem in Iowa and beyond. The AP reported that as the ground stays frozen less consistently, more winter days bring runoff conditions that can carry farm chemicals into waterways used for drinking water.
In Iowa, the AP said Des Moines Water Works had to filter for dangerous nitrates during January and February—only the second time in more than 30 years that the city’s water system had needed to do so during that period. The report said the filtration costs were about $16,000 a day, a figure that underscores how weather-driven water-quality swings can translate into day-to-day operating expenses.
The nitrates that contaminate drinking water can originate from fertilizer and pesticides used on fields, the AP reported. Rain or snowmelt can move nitrogen and phosphorus through soils and into waterways such as the Raccoon and Des Moines rivers, where they can become a health concern. The AP said the problem is less common in winter under more typical freezing conditions, but this year’s winter events forced the unusually costly filtration response.
Justin Glisan, Iowa’s state climatologist, pointed to future risk in the way nitrate events may change with warming. The AP reported Glisan as saying, “We are more apt to see these in the future. Are they going to occur every year? No. But the ingredients are there for them to potentially occur more often.” The report described how warming winters can reduce how reliably soils remain frozen, allowing more winter runoff pathways.
Researchers said the changing pattern is tied to multiple overlapping drivers, including snow that melts or falls as rain on thawed ground and weather swings that send water through soil more quickly. The AP reported that intense dryness followed by intense wetness can move large amounts of water through the soil and carry farm nutrients downstream, and it also cited Glisan describing more frequent “winter flip-flops” as Arctic regions thaw and shift from frigid, snowy conditions toward warmer, less snowy weather.
Beyond Iowa, the AP said nitrate pollution is a major concern for low-income and rural residents across the United States. Samuel Sandoval Solis, a professor at the University of California-Davis and an extension specialist in water resources management, said communities that already have infrastructure such as filtration can manage nitrate levels, but others cannot. The AP also noted that about 15% of the U.S. population relies on private wells for drinking water, citing the U.S. Geological Survey, and that nitrates can seep into those wells.
The AP reported that testing well water and filtering it at home can cost hundreds of dollars a year, creating pressure on smaller communities and households. It said small communities whose water treatment systems are not equipped to filter nitrates face expensive decisions about how to respond. In Illinois, the AP said program staff have increasingly tied the issue to climate conditions, with Joan Cox, program manager for the Illinois Nutrient Loss Reduction Strategy, describing how the role of climate change is appearing more explicitly in yearly reports.
Scientists and researchers are also working to understand what more frequent winter runoff will mean for ecosystems. The AP reported that Carol Adair, a professor at the University of Vermont who has studied how rain-on-snow events could worsen nutrient pollution, said scientists know more nitrogen travels downstream in winter but are still determining whether that results in more overall pollution. The AP also quoted Adair as saying there is little known about the consequences of the changes on ecosystems and suggesting that winter processes can send more nutrients further downstream, including to areas such as the Gulf of Mexico where nutrient pollution contributes to low-oxygen conditions.
Food and Water Watch staff attorney Dani Replogle told the AP that attempts by factory farm operators to time manure and fertilizer applications based on precipitation expectations are becoming less reliable. The AP reported Replogle as saying the strategy is “increasingly not a successful strategy because everything is becoming so unpredictable,” reflecting the broader challenge of managing agricultural nutrient loss as weather becomes harder to plan around.
The AP said regulating nutrient pollution has proven difficult, especially in agricultural states such as Iowa where the farm lobby has opposed mandatory rules. It reported that Trump’s EPA delisted seven Iowa waterways from the federal Impaired Waters List, a move that under the Clean Water Act would have required limits and state action; Food and Water Watch said it intends to sue. On the utility side, the AP reported Des Moines Water Works CEO and general manager Amy Kahler describing the need for resiliency planning for a future that includes more winter nutrient pollution, while arguing that upstream polluters should do more to prevent contamination.
Kahler told the AP that there are two paths: conservation and responsible watershed practices, or spending large sums on treatment solutions. The AP reported her as saying, “There really are two paths. One is conservation efforts and responsible watershed practices. And the other is spending hundreds of millions of dollars in treatment solutions.” The report also referenced earlier litigation, saying the federal government sued in 2015 for millions of dollars the agency said it was being forced to spend to filter unsafe levels from drinking water taken from the Des Moines and Raccoon rivers, and that a judge later dismissed the lawsuit.
Sources cited in the AP report described nitrate pollution as both an environmental and a public-health issue, with costs that can fall quickly on water utilities and households when weather-driven runoff sends nutrients into drinking-water sources. With warming trends affecting the timing and intensity of winter conditions, officials and researchers said future planning will likely need to account for more frequent—though not necessarily annual—winter nitrate pollution events.