Bivariate Visualization of Population Density by Public and Private Drinking and Wastewater Infrastructure in Florida

Understanding how populations rely on public versus private drinking water and wastewater systems is essential for infrastructure planning, environmental management, and publichealth preparedness. Conventional parcel-based maps depict drinking-water and wastewater systems separately, forcing planners to compare multiple univariate maps and obscuring relationships between paired systems. Parcel maps also emphasize land areas rather than population served, underrepresenting the human dimension of infrastructure use. These limitations are especially consequential in states such as Florida, where private wells and onsite wastewater systems coexist with expanding municipal utilities and produce spatially heterogeneous service patterns that are difficult to interpret using traditional cartographic techniques. This study introduces a bivariate, population-weighted visualization method that represents drinking-water and wastewater infrastructure within a single gridded map. Using the Florida Water Management Inventory (FLWMI) a statewide, parcel-level geospatial database maintained by the Florida Department of Health each 1- km grid cell encodes the proportion of residents relying on public and private systems, revealing fully public, fully private, and mixed-service areas. By integrating population density with bivariate symbology, the approach enhances analytical clarity and communicative value. Beyond Florida, the method offers a replicable framework that emphasizes human impact and supports evidence-based decision-making across regions of the southeastern United States where mixed infrastructure configurations are common.