Per- and polyfluoroalkyl substances (PFAS) contamination in watersheds is a growing concern. PFAS substances can cause adverse health effects such as cancers, liver damage, elevated cholesterol levels, weakening immune systems, and congenital disabilities. Discharge from factories, industrial plants, airports, agriculture, or wastewater treatment facilities can introduce PFAS contaminants into river systems, serving as a critical resource for drinking water supply, wildlife, agricultural productivity, and recreational activities. Boxelder Creek, the Big Sioux River, and the Missouri River are three riverine systems in the upper Midwest. The Boxelder Creek watershed has a small average discharge of 15 cubic feet per second and rural regional population of 14,512 in South Dakota; the Big Sioux River watershed has a medium average discharge of 246 cubic feet per second and mixture of the rural and urban regional population of 210,734 in South Dakota, and the Missouri River watershed near Omaha, NE, with a large average discharge of 23,821 cubic feet per second and urban regional population of 480,194 in Nebraska. These river systems are particularly vulnerable to PFAS contamination, as urban and industrial runoff, exacerbated by spring flooding from snowmelt and rainfall, can introduce these persistent chemicals into their waters. All three watersheds have airfields commonly identified as locations with aqueous film-forming foam use. We will assess the effects of population/land use, dilution (seasonal discharge), and watershed on PFAS distribution. Evaluating the pathways of PFAS contamination in watersheds and the influence on municipal, agricultural, and recreational uses will help inform future planning and potential cleanup.