CHARACTERIZING PRESENT AND FUTURE NITRATE LOADING IN A GROUNDWATER-DOMINATED AGRICULTURAL WATERSHED OF A COASTAL LAGOON

Abstract

Basin Head is a coastal lagoon in northeastern PEI, where Nitrate-nitrogen (NO3-N) is conveyed from the agricultural watershed to the eutrophic lagoon via intertidal groundwater springs and groundwater-dominated tributaries. The objective of this thesis was to characterize nitrate loading to the lagoon under present and future climate conditions using various field and modelling methods. Stream gauging and water quality sample results for four tributaries and three groundwater springs were used to develop a representative summer NO3-N loading rate for the lagoon (401 kg/month). A hydrologic model (SWAT+) revealed that out of six global climate models, only one (MRI-ESM2-0 SSP585) resulted in a statistically significant increase in NO3-N loading (p-value < 0.05) from historical (1990-2020) to future (2070-2100) periods. Using this climate scenario, one simulated best management practice (altered crop rotation) resulted in a significant NO3-N reduction. Results provide guidance to environmental management in coastal agricultural watersheds in a changing climate.