Nutrient and Carbon Loading from Forested, Urban, and Agricultural Watersheds during Extreme Climatic Events

Abstract:

Extreme climate events, such as high intensity rainstorms, are expected to rise dramatically per climate change forecasts. Thus, understanding nutrient and carbon responses to these events is essential to mitigate water quality concerns. We used high-frequency sensor nitrate-nitrogen (NO₃^--N), total organic carbon (TOC) and dissolved organic carbon (DOC) data to examine hot moments of nutrient and carbon transport in three watersheds dominated by different land use (forest, developed and agriculture) in coastal Rhode Island over three years. With these data we determined the proportion of annual loading that occurred during brief, high-intensity storm events. Initial results suggest that NO₃^--N, TOC, and DOC loads increased dramatically during storm events in the agricultural watershed - as much as ten-fold over baseflow – with lower increased loads generated during the storms in urban and forested watersheds. We also examined if sensor-collected data (NO₃^--N, TOC and DOC) could be used as surrogates in predicting non-sensor constituents (e.g., total N, total phosphorus, and ortho-phosphorus) collected from grab samples during baseflow and storm flow and analyzed in the laboratory. Sensor data provides high resolution data to determine rapid responses of concentrated flow events and assist in predicting trends with other water quality parameters. Implementation of agricultural BMPs and maintenance of forest areas may be essential to mitigate water quality impacts with extreme storm events.