Future climate change impacts on streamflow and nitrogen exports based on CMIP5 projection in the Miyun Reservoir Basin, China

Abstract

The projection of streamflow and nutrient exports are essential for future water resource and environmental management plans under climate change. This study investigated the responses of streamflow and total nitrogen (TN) loading to future climate scenarios in the Miyun Reservoir Basin (MRB) by coupling a physical process-based hydrologic and water quality model, Soil and Water Assessment Model (SWAT) and 42 statistical downscaled climate projections on the basis of CMIP5 models. Future climatic projections during the two future periods (2021–2035 and 2051–2065) under RCP4.5 and RCP8.5 emission scenarios, primarily precipitation and temperature, were used to drive the calibrated SWAT model. Results show that the MRB would be warmer and more humid. The ensemble mean changes in average annual precipitation (mean temperature) are expected to be more than 5.4% (0.6°C) during the period of 2021–2035 and 12.5% (1.6°C) during 2051–2065. Future streamflow and TN loading projection are expected to increase in two future periods. Meanwhile, the changes in streamflow and TN loading would be higher in summer than in other seasons. The uncertainty ranges in TN loading projection is larger than that in streamflow projection. The probability that streamflow and TN loading increase would be higher in the period of 2021–2035 than in 2051–2065. This study could be of use for providing an insight into the availability of future streamflow and pollution control for the MRB.