Predicting the relationship between the spatial organization of animal farms and water quality in the Maumee River Watershed

Abstract

Animal agriculture in the United States (US) continues to industrialize and expand, transforming agricultural landscapes and raising water quality concerns, particularly in northwest Ohio. While animal feeding operations (AFOs) tend to cluster spatially, a phenomenon linked to increased nutrient loading nationwide, there is a critical need to evaluate how AFO clustering influences water quality at regional watershed scales. In this study, we analyzed the local-scale impacts of AFO spatial clustering on water quality across the Maumee River Watershed (MRW). Using animal farm locations and a 20-year water-quality dataset (2000–2020), we quantified AFO spatial clustering using a nearest-neighbor index and applied linear mixed-effects models (LMMs) to assess its influence on total phosphorus (TP), total Kjeldahl nitrogen (TKN), and water temperature (Tw). Overall, HUC10-level watersheds with clustered AFO patterns were associated with elevated nutrient concentrations and stream temperatures. Watersheds with clustered AFOs had, on average, 0.86 mg l−1 higher TP and 0.46 mg l−1 higher TKN stream concentrations than watersheds with dispersed AFOs. Nutrient concentrations peaked in clustered watersheds during the summer, with mean TP and TKN concentrations of 2.05 mg l−1 and 1.81 mg l−1, respectively, consistent with periods of increased manure application. Watersheds with clustered AFOs also exhibited Tw averaging 1.64 °C higher than dispersed watersheds and experienced warmer fall and winter stream conditions. LMMs revealed that omitting spatial configuration limits model accuracy. Including spatial pattern as a fixed effect explained 31% and 68% of variance in TP and Tw, respectively. While environmental predictors such as percent wetlands, croplands, and forest improved model performance, land cover composition alone was insufficient to explain observed water quality patterns. Regional research has focused heavily on the effects of row-crop agriculture and isolated manure application, overlooking the landscape-scale effects of AFO spatial organization. Our findings show that incorporating AFO spatial patterns into watershed-scale assessments may improve predictions of water quality outcomes and can inform management strategies to build resilience in Great Lakes coastal systems.