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 has mapped streamflow alterations across the continental U.S., providing a wealth of data for determining societal impacts on ecosystems.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 has mapped streamflow alterations across the continental U.S., providing a wealth of data for determining societal impacts on ecosystems.