Simulating Hydrology and Water Quality to Predict Stream Discharge, Nitrate Loads Under Climate Change Scenarios in Maidford River Basin, Rhode Island Using SWAT Model

Abstract:

A Soil and Water Assessment Tool (SWAT) model was developed for the Maidford River Basin (MRB), a 4.4 km2 watershed dominated by agricultural land cover (41%) to simulate hydrology and water quality for the prediction of stream discharge, and nitrate loads under climate change scenarios. The study utilized a SWAT-CUP calibration and uncertainty estimation tool to calibrate streamflow and nitrate loading using Sequential Uncertainty Fitting-2 (SUFI). This procedure resulted in Nash-Sutcliffe Efficiency (NSE) goodness-of-fit statistics that met literature guidelines for monthly mean stream discharge and daily nitrate load. We investigated how projected changes in climate affected simulated nitrate (NO3−) and organic nitrogen discharge for MRW for years 2020–2070. The SWAT simulations and ensemble climate change scenarios resulted in a warmer and wetter climate with greater and more extreme discharge in all seasons except summer where the models indicate a somewhat higher probability of extreme low flows. The model predict the possibility of greater high flow events and nitrate loads in a wetter and warmer future.

Keywords: Nitrate, SWAT, hydrology, water quality