Hydrological and water quality simulation and future runoff prediction under CMIP6 scenario in the upstream basin of Miyun Reservoir

Abstract

AbstractWater resources are a key factor restricting human survival and social and economic development. The Miyun Reservoir, which is the only surface drinking water source in Beijing and the water storage reservoir of the South-to-North Water Diversion Project, plays a decisive role in ensuring water-use sustainability of the capital. This study focused on the Baihe River Basin, which is one of the important inflows of the Miyun Reservoir. The mathematical data on the climate and hydrological changes of the Baihe River Basin over the past 30 years were obtained, and the evolution law of the Baihe River runoff and its influencing factors was analyzed. Our analysis used the data obtained via multi-source meteorology to establish the Soil and Water Assessment Tool (SWAT) model of the Baihe River Basin. Sequential Uncertainty Fitting version 2 (SUFI-2) and Generalized Likelihood Uncertainty Estimation (GLUE) were used to simulate runoff from 1990 to 2017 on a monthly scale, along with sediment, total nitrogen (TN), and total phosphorus (TP) contents from 1990 to 2010. Then, the parameter uncertainty of the SWAT model and the applicability of the SWAT model in the Baihe River Basin were determined. The land-use transfer matrix showed that land-use changes are complex and the transformation forms are diverse. The simulation results showed that the transformation of land-use patterns in 1990 and 2010 had slight impacts on the hydrologic and water quality of the basin. By identifying the key source areas of non-point source pollution in the basin, the impacts of three management measures on the hydrological and water quality of the basin were simulated. The results showed that the reductions in flow rates, sediment content, TN, and TP (4.37, 31.93, 23.13, and 35.30%, respectively) obtained through terrace engineering were significantly better than those acquired via stubble mulch and contour planting. Additionally, this study uses the Sixth International Coupling Mode Comparison Program (CMIP6) climate change scenario and the BCC-CSM2-MR climate model coupled with the corrected SWAT model to predict future runoff, thereby providing references and suggestions for managing the Baihe River Basin and the Miyun Reservoir.