Assessing the Impacts of Climate Change on Nitrate-Nitrogen Concentrations in the Des Moines River

Abstract

Nitrate-Nitrogen (NO3-N) pollution in bodies of water harms aquatic and human communities. NO3-N notably degrades drinking water quality through eutrophication, and causes hypoxic conditions that harm aquatic life. Population increase has led to a boom in agricultural production, leading to increased fertilizer use, and excess nutrients from fertilizers are found in critical water bodies. The Des Moines River in North-Central Iowa receives a significant amount of excess nitrogen due to tile drainage systems in the surrounding areas. Communities that rely on water from the Des Moines River have been impacted by orders to reduce water use. As climate change progresses, North-Central Iowa will likely experience an increase in extreme precipitation and temperature events. In this study, I assess the impact of climate change on flow, as well as NO3-N levels in the Des Moines River near Des Moines, based on three future scenarios (Shared Socioeconomic Pathways SSP2-4.5, SSP3-7.0, and SSP5-8.5). The results of this work point to an increase in the intensity and frequency of peak flow events, and depend on the selected future scenario and climate model. NO3-N results agree much less between climate model and scenario, but show concentrations above the threshold above maximum contaminant level for drinking water, suggesting a need for new management strategies and agricultural practices.