Comprehensive river assessment identifies which U.S. waterways need urgent conservation efforts

Researchers have completed the first comprehensive evaluation of rivers and streams across the lower 48 U.S. states, rating each on connectivity, floodplain condition, water quality, and flow alterations. The study reveals that only 6 percent of American rivers are both healthy and adequately protected, though many others could be restored with targeted repairs. The detailed mapping provides specific guidance on where conservation funding would generate the greatest ecological benefits as climate change intensifies pressure on freshwater ecosystems.

This study represents the first time researchers have systematically evaluated waterways across the continental United States using a unified framework. The assessment examined one-third of the nation's total stream distances, applying four ecological criteria to determine each watershed's capacity to support aquatic organisms as environmental conditions shift. The methodology incorporated existing biodiversity research from across all 44 participating states, accounting for regional variations in climate and geography.

The research identifies dams as a primary threat fragmenting river systems into over 9,000 disconnected segments that prevent fish migration and access to temperature-regulated habitats. While the findings indicate that most degraded rivers could potentially be restored through targeted interventions—such as removing specific dams or reducing agricultural runoff—the current data reveals the challenge ahead: nearly 94 percent of assessed waterways fall short of being both healthy and adequately protected.