Variations in Reference Evapotranspiration and Associated Driving Forces in the Pearl River Delta of China during 1960-2016

Abstract

 Recent climate warming and rapid urban development in the Pearl River Delta (PRD) of China exerted great impacts on the reference evapotranspiration (RET), which in turn affects the management of water resources and the quality of urban environment. The objectives of this study are to examine (i) the temporal variability of RET in PRD, and (ii) the underlying causes responsible for the temporal variation in RET across space inside the PRD. The results indicate that: (1) The RET in PRD had an overall increasing trend caused by the increase of construction land during 1960-2016. (2) The increase of surface albedo caused by land cover conversion from woodland to grassland played an important role in the noticeable decline of RET in Guangzhou and Zengcheng. (3) The dominant factors triggering RET variation varied across space in PRD. In detail, the decline of sunshine duration decreasing Rn, and the decline of wind speed weakening energy exchange, were the dominant factors in decreasing RET in Guangzhou and Zengcheng. In contrast, daily maximum temperature, daily minimum temperature and relative humidity, which were the factors causing the increase of vapor pressure deficit, were responsible for RET increase in Taishan, Zhongshan and Shenzhen. Overall, our results indicated that RET in PRD exhibited strong spatial heterogeneity due to differences in land use change and climatic conditions. Therefore, the improvement of water resources management and urban environment in PRD should consider the spatial variation and underlying forces of RET changes.