Evaluation of water conservation function of Beijiang River basin in Nanling Mountains, China, based on WEP-L model

•WEP-L model is an effective measure to quantitatively evaluate water conservation.•Multi-temporal scales of water conservation were quantitatively evaluated.•Quantity of water conservation were different under extreme precipitation.•Precipitation was the main factor affecting water conservation. Water conservation is one of the most critical ecosystem service functions of river basins and is an important indicator of regional eco-environmental conditions. Beijiang River Basin (BRB) is an important water source and ecological barrier for the Guangdong-Hong Kong-Macau Greater Bay Area (GBA), and its water conservation function is of widespread concern. In this study, based on the hydrological model WEP-L (Water and Energy transfer Processes in Large River basin), and the water balance principle, we analysed the multiple time-scale characteristics of water conservation in the BRB during 1960–2018 and revealed the response of water conservation to climate change based on scenario setting and hydrological simulation. The results showed that annual water conservation exhibited an insignificant reducing trend of −4.69 mm/10a. Water conservation reduced insignificantly in spring, summer, and autumn, while it showed a nonsignificant increasing trend of 4.69 mm/10a in winter. The spatial distribution of water conservation in the BRB was low in the south and high in the north, mainly due to the spatial distribution of land use. Precipitation was the main factor affecting water conservation. The results can provide a reference for water resource planning and management, and provide a theoretical foundation for ecosystem restoration and reconstruction.