Oklahoma has been exemplary at cleaning up its streams. By some measures, more than any other state.

A big part of the solution was simple: Give cows clean drinking water and keep them out of the streams.

When one farmer tried it, he quickly saw results. His veterinarian bills went down and wildlife returned to the area.

Grant Victor wasn’t sure what to expect when he decided to fence his cattle off from Horse Creek, which wends through northeast Oklahoma, bisecting his family’s pastures and cropland.

The original plot of land has been in his family since the 1890s, and they added to it over the years. But a century’s worth of bovine traffic had left the creek’s banks muddy and bare, and its waters thick with kicked-up sediment and animal waste.

In 2016, Mr. Victor resolved to change

Keep reading this article on The New York Times Energy & Environment.