Excess phosphorus and nitrogen from municipal wastewater, urban runoff and agriculture contribute to a growing problem in water quality across the country. The issue is particularly bad in the Midwest, where 1.2 billion pounds of excess nutrients run off of farm fields and into the Gulf of Mexico each year, according to models created by the U.S. Geological Survey.
Runoff from Midwestern farms can affect the quality of local drinking water when it leaches into wells and groundwater that municipalities draw from. Nitrate fertilizer consumption poses serious health risks, including thyroid disease, colon cancer and even death in infants.
Those same nutrients run downstream and contribute to the expansion of the “dead zone” in the Gulf of Mexico, a phenomenon that costs local economies billions of dollars in damage to fisheries and marine habitat every year.
The U.S. Geological Survey released an interactive map in 2020 that shows a model of the most significant sources of nutrient runoff: fertilizer, manure and nitrogen fixing plants like soybeans, alfalfa and clover, which add nitrogen to the soil naturally.
Models from the U.S. Geological Survey’s SPAtially Referenced Regression On Watershed Attributes shows an estimate of the average annual load of nitrogen and phosphorus from major sources delivered from Midwestern states to the Gulf of Mexico.
An estimated quarter of all phosphorus runoff and 40% of all nitrogen runoff from farming practices in the Midwest comes from just three states — Illinois, Indiana and Iowa. Commodity crops that require fertilizer and concentrated animal feeding operations contribute to this.
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