Gallery riparian forests develop because water in these habitats is readily available for root uptake by large woody plants such as cottonwood and willow trees. These forests are highly productive and are valued for wildlife habitat, watershed protection, and recreation. Nevertheless, impoundments and diversions of surface water have resulted in the decline of riparian ecosystems throughout the western United States. Recently, the Central Utah Water Conservation District has begun renovation of the Red Butte Canyon Reservoir Dam near Salt Lake City, UT, requiring the reservoir above the dam be drained for a duration of two years. Since the dam was constructed (1930), stands of cottonwood and willow have established in the large delta that has formed at the mouth of the reservoir. The removal of the reservoir, and hence the primary water source for these trees provides a unique opportunity to gauge how riparian trees respond to surface water removal. Measurements of stem sap flux, plant water status, xylem function and anatomy, and leaf chemistry and morphology is currently being investigated over a four year period to capture pre-drawdown (yr1), drawdown (yrs 2 and 3), and post drawdown (yr 4) of the reservoir.