Risk Indicators for Identifying Critical Source Areas in Five Arkansas Watersheds

Abstract

Abstract. Change point analysis was used to explore the interactions between watershed characteristics and concentrations of nitrate-nitrogen, total nitrogen, soluble reactive phosphorus, and total phosphorus in streams within the Ozark Highlands, Arkansas Valley, and Ouachita Mountains ecoregions of Arkansas. Thresholds were identified for multiple watershed metrics used to predict water quality, including percent forest in the catchment, agricultural and forested land use in the riparian buffer, stream density, and poultry house density. Based on the observed relationships from the sampled watersheds, we propose four risk indicators to improve the identification of critical source areas for NPS pollution mitigation: subwatersheds that have less than 50% forested area within the drainage area, less than 50% forested area in the riparian buffer zone, more than 0.9 poultry houses km-2, and a stream density that exceeds 50 m ha-1. Keywords: Nonpoint-source pollution, Source water protection, Watershed management.