RESPONSE OF NUTRIENT AND SEDIMENT CONCENTRATIONS TO RAIN EVENTS IN THE CHARLOTTE CREEK WATERSHED, NEW YORK

Nutrient and sediment concentrations of stream water change in response to rain events that increase the discharge. These high volume and concentration events are still lacking monitoring data and the dynamics are poorly characterized. The purpose of this project is to characterize the correlation between rain events and nitrogen, phosphate, and sediment concentrations in the Charlotte Creek watershed. This creek is a tributary to the Susquehanna River in New York State that ultimately runs to the Chesapeake Bay. Water samples were collected daily in June 2021, as well as before, during, and after storm events in September and October of 2021. In addition, water sampling was conducted in May and September 2021 from both tributary streams and the main stem of Charlotte Creek, to help understand spatial and temporal variations within the watershed. Field parameters such as pH, temperature, electrical conductivity, and dissolved oxygen were measured on-site. Turbidity as a proxy for suspended sediment concentration was measured upon arrival to the laboratory. Then samples were filtered and preserved for nitrate and phosphate analysis, which was conducted by ion chromatography. Nitrate, phosphate, and sediment loads were estimated based on rain event size, volume of discharge and measured concentrations. Preliminary results indicate that Charlotte Creek’s nitrate levels immediately respond to any rain events, while phosphate and sediment loads only increase with large storms. These findings also indicate that nitrate is mobilized with any amounts of run-off water, while phosphate is attached to sediment and only gets mobilized above a certain size run-off (rain) event. To further test these preliminary relationships between precipitation, discharge, chemical, and physical parameters, stream monitoring will continue capturing different size storm events. In addition, to better understand the spatial and temporal distribution of chemical and physical signatures, the tributaries will also be further characterized.