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Abstract
Variability in freshwater supply creates challenges for managers balancing social and ecological water demand worldwide. Management actions are often focused on maintaining a consistent domestic water supply with minimal consideration of corresponding tradeoffs in freshwater ecosystems. This dissertation examines social, ecological, and engineering components through three socio-ecological studies focused on Puerto Rico’s freshwater system. First, I evaluated long-term effects of low-head dams paired with water intakes on longitudinal riverine connectivity for freshwater shrimp (Chapter 2) and four other migratory animals (snails, gobies, mountain mullet, and American eel; Chapter 3) in northeastern Puerto Rico. An analysis of stream discharge and water intake rates show decreased habitat connectivity for native shrimp as a result of intakes and dams constructed over the last 3-4 decades. Conversely, other migratory animals, including snails, eel, and mullet, are limited by barrier height, which reduces their overall habitat availability but also makes their connectivity less sensitive to increases in water withdrawal rates. These studies emphasize the importance of water managers considering downstream and upstream temporal variation in connectivity, especially in relation to the sustainability of diadromous aquatic fauna metapopulations. Second, Puerto Rico’s environmental flow law and practice are evaluated through interviews with state and federal water managers (Chapter 4). Mismatches in de jure (legislative directives) and de facto (execution of legislation) water management can be partially explained by the political accountability of state agencies, restricting environmental flow legislation enforcement. Third, a socio-ecological systems lens is applied to examine the resilience of stream ecosystems and the municipal water supply to extreme climatic events, specifically hurricanes and droughts (Chapter 5). Using systems models and historical event analysis, this study concludes that some historical management actions designed to increase social drought resilience has ultimately reduced overall system resilience when viewed relative to both infrastructure and ecological outcomes. Overall, this dissertation informs a holistic approach to freshwater management in Puerto Rico by examining the role of temporal variability in ecological connectivity; differences in water infrastructure effects across several taxa; limitations to water management legislation enforcement; and feedbacks across social and ecological processes that undermine and maintain system-wide resilience.