Best Management Practices (BMPs) are commonly employed to mitigate nutrient transport from farmland to water bodies. In this study, we utilize a hybrid climate assessment approach to evaluate changes in water quality as well as the effectiveness of agricultural BMPs under changing climate conditions. The focus of our investigation is the Qu'Appelle River Basin, a vast and predominantly agricultural region in the Canadian Prairies. We assess the performance of BMPs in terms of total nitrogen delivery under both current and projected future climates, using an ensemble of downscaled climate model simulations under alternative future scenarios. Our findings reveal the suboptimal efficacy of historical BMPs in adapting to future climate conditions. To address this issue, we explore the concept of hardening BMPs, tailored to mean ensemble projections. While these adapted BMPs demonstrate improvements in both nitrogen removal magnitude and cost compared to historical BMPs, their efficiency experiences a systematic decline as temperatures rise. We advocate for the immediate implementation of BMPs as a proactive measure before climate conditions become more challenging. However, in the long term, we recognize the necessity of developing innovations in physical, chemical, and biological remediation technologies to effectively manage nitrogen loads from agricultural activities.