Abstract: Watershed water and carbon cycles are closely linked through plant photosynthesis and evapotranspiration (ET). Simulation of coupled water-carbon cycles at the watershed scale is important for the comprehensive management of water and carbon resources. By improving the WaSSI (water supply stress index) eco-hydrological model, we established and verified a water-carbon coupling simulation model for the Pearl River Basin in south China (WaSSI-PRB). The Pearl River Basin was divided into 1715 watersheds. The simulations of three water-carbon flux parameters, such as runoff, ET and gross primary productivity (GPP), were verified with 1980-2004 as the calibration period and 2005-2016 as the validation period. The Nash-Sutcliffe efficiency coefficient (NSE) and the coefficient of determination (R²) of the simulated runoff at the controlling hydrological stations of Xijiang, Beijiang and Dongjiang were greater than 0.80 during calibration period and greater than 0.75 during validation period. Compared with MODIS, PML, SSEBop, VPM and other large-scale remote sensing data products, WASSI-PRB showed a better performance in capturing the spatiotemporal variations of ET and GPP. In general, WaSSI-PRB model had good applicability in the study area, and could be used as an effective tool to quantitatively analyze water-carbon balance and their responses to environmental changes in the Pearl River Basin.

Key words: WaSSI-PRB model, coupling of water and carbon, Pearl River Basin, applicability assessment