Assessing equitable access to safe and affordable water during COVID-19: Agent-based modeling for tap water avoidance behaviors

Water distribution systems (WDSs) should deliver safe and affordable water for communities, yet consumers are regularly exposed to tap water that violates federal guidelines for pathogens and chemicals. In response to reduced water quality, consumers may shift demands away from tap water to bottled water, increasing household water spending. Intra-system water quality fluctuates with changes in demands, a consequence observed during the COVID-19 pandemic. This research develops the COVID-19 social-distancing and tap water avoidance agent-based model (COST-ABM), which simulates water quality in a water distribution network and decisions to avoid tap water and purchase bottled water. COST-ABM is developed to assess equitable access to affordable water. Agents represent water consumers that decide to avoid tap water by purchasing bottled water for cooking, cleaning, and hygienic end uses, reducing demand from the system. The agent-based model is tightly coupled with a water distribution system model that calculates the spatiotemporal dynamics of water quality in a pipe network, which is used in agent decision-making. Equity is evaluated in a bottom-up approach using the cost of tap and bottled water as a percentage of household income, calculated at each household. The framework is applied for a virtual water distribution system, and results demonstrate economic inequities in water affordability. This research presents a framework to assess equity in a WDS based on tap water avoidance and water affordability and can be used to facilitate infrastructure management that provides equitable access to safe and affordable water.