This course describes the existing condition of the Gila River in the Cliff-Gila Valley and examines the potential impacts of CUFA diversion and climate change on the riparian and aquatic ecosystem. Scientists who have expertise in some aspect of the Gila River’s hydrology and ecology wrote and contributed to this assessment. Flow variability is the defining feature of the Gila River in the Cliff-Gila Valley—creating a multi-aged riparian forest, floodplain wetlands and an array of aquatic and floodplain habitats that supports a diversity of wildlife, including six threatened and endangered species.
River flows fluctuate widely from one year to another and also within a year. Flows during each season have specific ecological functions and maintain diverse habitats. Examples of the relationships of how river flows directly influence biodiversity will be presented.
In addition, two scenarios will be described: 1) diversion allowed under the Arizona Water Settlements Act and 2) climate modeling and corresponding changes in streamflow. Both scenarios will reduce the number and magnitude of mid-size flows in the 400-4,000 cubic feet per second range. If the frequency of these flows is reduced, the floodplain will be inundated less often, with decreases in the alluvial aquifer recharge, faster declines in surface water and groundwater, and increased surface water temperatures. These potential changes will affect components of the Gila River ecosystem in a variety of ways, which will be the focus of this presentation.
1. Characterize hydrology and define how flows shape and sustain the ecosystem.
2. Assess how proposed diversion and climate change will alter flows and impact riparian and aquatic species.