Stina Sieg/KJZZ

Interior of the Grand Canyon.

The U.S. Geological Survey has published a study on uranium content in wells and springs in the Grand Canyon region, but the work is far from over.

The study examined about 200 water sources and found that only a fraction of them had elevated concentrations of uranium. Most were within federal standards for drinking water.

Fred Tillman is a hydrologist who led the project. He said that it’s premature to draw too many conclusions from the report, which was a snapshot of about four decades.

"What we know about the groundwater system in that area is that some of the flow paths are really long, so it can take an extensive amount of time to get from point A to point B, so if we’re looking for effects from uranium mines on groundwater resources, they might not show up at spring sites for hundreds, to possibly thousands of years," said Tillman.

Tillman added the work is ongoing, and that the agency continues to monitor wells and springs in the area.