This project will demonstrate the application of an integrated suite of models to holistically analyze the impacts of climate change and extreme weather (specifically, rising sea and/or groundwater levels, increasing groundwater salinity, and changing precipitation patterns) on groundwater, stormwater, and wastewater infrastructure at U.S. military installations. This modeling toolbox will allow users to identify, evaluate, and prioritize investment in interventions to sustain water infrastructure systems and thus improve water security while reducing overall cost to the Department of Defense (DoD). This project will demonstrate the generalizability of this toolbox by screening six military installations across a range of physiographic settings to evaluate the vulnerability of water infrastructure at these sites and availability of data to fully characterize risk using the modeling toolbox. The primary focus will be on coastal locations, but at least one inland location will be included to explore generalizability to those settings. For Dover Air Force Base, a coastal site with high vulnerability and good existing data availability, the project will demonstrate the utility of this toolbox by developing a site-specific integrated model and performing a full evaluation of climate change vulnerabilities and a cost-benefit analysis of possible interventions. In addition to providing a detailed assessment of this demonstration site, the project team will develop guidance including standard operating procedures to facilitate the adoption of the modeling toolbox at other DoD settings.

The modeling toolbox will use site-specific predictions of changing rainfall patterns and rising water levels as inputs to an integrated model that simulates groundwater flow and salt transport, stormwater and sanitary sewer flow, and stormwater best management practices. The toolbox will also contain coding packages to evaluate impacts to groundwater flooding and stormwater management, wastewater conveyance and treatment, and (where applicable) drinking water quality and impacted groundwater based on outputs from integrated model simulations. A key innovation lies in the way in which the project team will connect two state-of-the-art models, one for groundwater (the United States Geological Survey’s MODFLOW) and one for stormwater (the Environmental Protection Agency’s Storm Water Management Model), to evaluate impacts resulting from interactions among these processes. Based upon integrated model results from climate change scenarios, the project team will design possible intervention scenarios and use the integrated model and a cost-benefit analysis to evaluate the effectiveness of each option at protecting DoD water infrastructure and minimizing costs.

Current approaches for evaluating the impacts of water level rise and changing (intensifying) precipitation patterns on flooding evaluate these phenomena separately, neglecting the ways in which groundwater can link the two hazards and create compound flooding risks. Even when surface flooding does not occur, generally wetter subsurface conditions may have an overlooked impact on aging wastewater collection systems and the ability of the system to treat wastewater as expected. Saltwater intrusion, rising groundwater levels, and changes in recharge patterns may also impact drinking water sources and may increase impacted groundwater from legacy landfills and other pollutant sources. Without a framework for holistically evaluating these threats, DoD may underestimate the risk to coastal facilities and may be unprepared for the actual costs of climate change for water infrastructure. This project will develop a modeling toolbox to assess these interrelated threats and evaluate the cost-benefit of interventions, demonstrate its application at a coastal military installation, and provide a template for repeating the assessment at other coastal and inland sites facing similar threats.