1204368/1204396/1204478Sankarasubraman Arumugam/ John Kominoski/ John SaboNorth Carolina State University/University of Georgia Research Foundation Inc./Arizona State UniversityWater resource availability varies across the Sunbelt of the United States with a sharp East-West transition at 105 degrees W. Arid regions west of the 105th Meridian produce less runoff compared to humid regions in the East that produce greater than 40 cm of mean annual runoff. Consequently, reservoirs in the West are over-year systems holding multiple years of inflows, whereas reservoirs in the East are within-year storage systems with the need to refill the system in the beginning of spring. Accordingly, water policies also differ substantially with western states pursuing ("prior appropriation") and the eastern states following ("riparian rights") for allocation. These contrasting strategies also impact freshwater biodiversity with the ratio of non-native to native fish species being nearly 6 times higher in the West compared to the East. In spite of these cross-regional differences, both regions face two common stressors: (a) uncertainty in available freshwater arising from global climate change and (b) increased human demand due to population growth and consumption. Consequently, there is an ever-increasing need for an integrated assessment of freshwater sustainability under these two stressors over the planning horizon (10-30 years). The main objective of this study is to understand and quantify the potential impacts of near-term climate change and population growth on freshwater sustainability - defined here as integrating daily to annual flows required to minimize human vulnerability and maximize ecosystem needs (including native biodiversity) for freshwater - by explicitly incorporating the feedbacks from human-environmental systems on water supply and demand in various target basins spanning Arizona to North Carolina. Using retro-analyses involving AR5 multimodel climate change hindcasts, we will revisit how freshwater sustainability could have been better achieved over the past five decades across the Sunbelt. To couple the hydroclimatic and hydro-ecological system dynamics with the management of freshwater infrastructure systems, a two-level agent-based modeling framework will explicitly simulate adaptive behaviors and feedbacks between policy and consumers. This interdisciplinary project will involve collaboration among three universities, North Carolina State University (NCSU), Arizona State University (ASU), and University of Georgia (UGA). Findings from the AR5 retro-analyses will evaluate and recommend societal options (i.e., supply augmentation vs. demand reduction) for promoting future (2015-2034) freshwater sustainability across the Sunbelt. Cross-regional synthesis of policies and media sources for the targeted basins will identify de-centralized adaptive strategies that have been employed independently and collectively to maintain flows, increase supplies, or reduce demands. Utilizing the near-term hydroclimatic projections, PIs will quantify how current policies on reservoir operations and groundwater extraction could impact the reliability of future water supplies for cities and also alter the key attributes of hydrographs that are critical for maintaining freshwater biodiversity. In doing so, the project will also investigate the degree to which regions have pursued "hard path" (i.e., supply augmentation) vs. "soft path" (i.e., demand reduction) strategies by explicitly modeling potential societal interventions for freshwater sustainability. The educational goal of the project is to conduct an online distributed seminar in which Honors, MS and PhD students from three Universities with interdisciplinary backgrounds will produce a policy-oriented white paper based on the key findings. Based on the white paper, the project team will distribute a suite of podcasts on freshwater sustainability and climate change to middle and high school science programs from the targeted basin states as well as to key water policy institutions across the region. Podcasts, developed data, tools and publications will also be disseminated through the main project portal at NCSU, and additionally through the National Climate Assessment and ASU's Central Arizona - Phoenix LTER websites.