Determining the Sustainability of Springs and Baseflow Streams Through Ecological Flow Needs Assessment and Values-Risks Methodology

To determine the sustainability of water resources in two separate groundwater basins of Arizona, an ecological flow needs assessment and a water resources values-risks methodology were developed and applied.  Each process was collaborative, science-based, interdisciplinary, and adaptive.  An ecological flow needs assessment was adapted and applied to an unregulated, baseflow dependent river.  A separate process was developed to determine surface-water and groundwater sources potentially at risk from climate, land management, or groundwater use changes in a large regional groundwater basin in the same semi-arid region.  In 2007 and 2008, workshops with ecological, cultural, and physical experts from agencies, universities, tribes, and other organizations were convened.  Flow-ecology response functions were developed with either conceptual or actual information for the baseflow dependent river, and scoring systems were developed to assign values to categories of risks to water sources in the large groundwater basin.  A reduction of baseflow to a major river was predicted to lead to a decline in cottonwood and willow tree abundance, decreases in riparian forest diversity (with likely loss of birds), and increases in non-native tree species, such as tamarisk.  Loss of riffle habitat through declines in groundwater discharge and the associated river levels would likely lead to declines in native fish and amphibian species.  The scoring system for categories of value and risk was applied to four types of water resources (aquifers, springs, standing water bodies, and streams) in the groundwater basin.  The process was developed to allow water managers to assess and prioritize potential impacts to the biological, historical, or cultural aspects of the four types of systems from groundwater abstraction.  Because the processes are so time intensive, it is recommended that financial support is provided to not only outside experts, but for the tribal or agency resource managers to conduct the assessments.