The Truckee River is Nevada’s largest river system, and supports a unique haven of river, riparian, and terminal lake ecosystems in the arid Great Basin. Decades of intense diversions from the Truckee River caused terminal lake levels at the river’s outlet to drop severely, nearly eliminating endemic fish species and causing widespread reductions in riparian forest cover. Following this ecological collapse, increased attention to the decline of the river’s health led to implementation of new streamflow management policies, called Environmental Flows, to better protect the river and its dependent ecosystems. This field-based research project uses tree-ring growth to explore how decades of river management, including periods of both heavy diversion and subsequent environmental management, have impacted the health of the riparian environment through the lens of cottonwood tree growth.