Altering streamflow can endanger the ecosystems that rely on it, but researchers have lacked data on how human infrastructure has impacted streamflow in the U.S. Now, a study involving a Colorado State University researcher has mapped streamflow alterations across the continental U.S., providing a wealth of data for determining societal impacts on ecosystems. Up to 80% of rivers and streams in the contiguous United States have been modified to some degree by human structures. Understanding the relationship between these modifications and ecological responses is key to enacting management policies that balance societal and ecological water needs.