Colorado River Integrity Assessment

The Colorado River has been dramatically altered from its natural state and now rarely reaches its terminus in the Gulf of California. In partnership with the Walton Family Foundation, we sought to assess the wide range of anthropogenic factors that currently impact the freshwater ecological integrity of the Colorado River Basin and capture the results in a peer-reviewed publication, and an accompanying interactive tool. This represents the first comprehensive threat assessment of this iconic and deeply endangered river system. We quantified and mapped 69 individual threat indices with geospatial tools for each permanent, ephemeral, and intermittent stream segment within the Basin, encompassing a total of more than 1 million river kilometers. We selected these indices according to published ecological integrity assessments and informed by discussions during an expert workshop. In bringing together this wide variety of data sources, we revealed marked variability in spatial patterns of human-related threats across river segments and watershed; that the river basin is prone to human-related threats at multiple scales—from valley bottoms to upstream catchments—and that there are clear opportunities for targeted conservation actions in watersheds based on the intersection of human-related threats and other contextual factors. Although this assessment was specific to the Colorado River Basin, the principles and methods we applied are widely applicable to other basins.