Study regionWestern suburb of Changsha, Hunan Province, the central southern China.Study focusPlant transpiration plays a significant role in the terrestrial water cycle and is closely associated with ecosystem primary production. Summer drought in the study area poses a stress on plant water use and associated carbon assimilation in growing season. In this study, water use response of two evergreen tree species to variation in environmental conditions was examined during a severe summer drought.New hydrological insightsThe results show that a decrease in water use during the drought for both two species is closely associated with an increase in vapor pressure deficit and a decrease in stem water potential. The two species appear to be anisohydric, but to a different degree in response to the drought. The hydrodynamic water potential gradient (Δψ) maintains relatively constant with an average value of 0.59MPa for C. camphora, and 1.59MPa for O. fragrans. O. fragrans is less sensitive to drought than C. camphora, while C. camphora shows an effective survival mechanism via leaf shedding and dieback of shoots

The demand for social and economic development has promoted research into water resources. The combined effects of natural conditions and human activities on regional water resource usage are not well understood. The sustainable utilization of water resources was assessed in terms of supply (e.g., precipitation) and demand (e.g., ecological water resources footprint (EF_w)) sides in Hunan Province, China, from 2010 to 2019. The results showed that: (1) on the supply side, water resources were increased across Hunan Province. The spatial patterns of total water resources are significantly heterogeneous, with high values in the east and south, which are mainly affected by precipitation; (2) on the demand side, evapotranspiration was great in areas with high vegetation coverage. The EF_w was high in relatively developed areas. The mean percentage of agricultural EF_w remained dominant at approximately 60% with a steady decreasing trend, while that of eco-environmental EF_w increased; and (3) the sustainable utilization of water resources in Hunan Province is generally rational. Moreover, the potential for water resource development and utilization is really significant in eastern and southern Hunan Province. The findings are beneficial in providing an important scientific basis for policymaking relating to the efficient utilization of regional water resources.