Iowa is the U.S. state with the most factory farms: 10,830 of them, to be exact. The massive scale of animal agriculture in Iowa produces staggering amounts of manure, more than its fields of corn, soy and other crops can absorb.

This has a devastating effect on the state’s water. When too much manure is spread on fields, nitrates run off into the groundwater and nearby streams and lakes.

Small towns in Iowa can face months-long stretches when their water is undrinkable. Des Moines, the state capitol and largest city, operates a massive system to remove nitrate pollution from its water to the tune of $10,000 a day, the largest such system in the world when it was built. More than half of Iowa’s rivers and streams, and more than 60% of its lakes and reservoirs, failed water quality standards in 2024.

This water crisis is linked to an unfolding public health threat.