Evaluating Climate Change Impacts on Drinking Water Reservoirs and Wastewater System Resilience in Connecticut, U.S.A.

Societies depend on the proper functioning and resilience of critical infrastructure systems including those for drinking water and wastewater, but these systems are vulnerable to natural and anthropogenic stressors. For example, wastewater systems are especially susceptible to extreme weather events while drinking water systems are vulnerable to diminished source water quality — both of which can disrupt proper functioning. Climate change and human development, economic problems, and pollution further challenge water system resilience. Despite the criticality of these systems and known vulnerabilities, little scholarship exists that aims to interrogate their resilience. This dissertation attempts to narrow this gap in the literature by: (1) investigating the sensitivity of reservoir water quality and wastewater system resilience to climate variability and change; (2) developing adaptation strategies to help improve wastewater system resilience; and, (3) advancing knowledge of historical and potential future reservoir water quality changes. This dissertation evaluates wastewater system resilience and reservoir water quality in Connecticut because climate induced increases in air temperature, extreme precipitation, and frequency of large storms stress water system functioning in the Northeast, U.S. and many other north temperate regions around the world. Wastewater system resilience is assessed from a social sciences perspective using concepts of adaptive capacity and adaptive management. Results suggest human dimensions are important for building wastewater system resilience and that systems with managers who build and deploy diverse generic and specific adaptive capacities within an adaptive management framework are most resilient to storms. For drinking water systems, observations from six Connecticut reservoirs over sixteen years from 2003-2018 indicate: (1) thermal stability is increasing; (2) surface water temperature is increasing; (3) bottom water temperature is decreasing; and, (4) surface and average water dissolved oxygen is increasing. Future projections suggest extreme high surface water temperatures and thermal stability will increase significantly by midcentury (2041-2070). Toxic cyanobacteria blooms may occur more often in the future under these extreme conditions, especially in reservoirs where eutrophication and harmful algal blooms are already a concern. This research aids in understanding, predicting, and informing appropriate strategies for managing water quality and wastewater systems under a warming climate