Space-time Characteristics and Environmental Significance of Stable Isotopes in Precipitation at an Arid Inland River Basin

Abstract

This study was based on one complete hydrological year sampling of precipitation and meteorological data of the Shiyang River Basin in the Wuwei Station (1531 m a.s.l.), Minqin Station (1389 m a.s.l.), and Xidahe Station(2897 m a.s.l.) from July 2013 to July 2014. This paper aims to analyze temporal and spatial variation of stable isotopes in local precipitation, and discuss the impact of environmental factors during precipitation. The stable isotope evolution correlation with temperature, humidity, precipitation, vapor pressure, and average relative humidity is analyzed. The results show that:①During the study period, the stable isotope of precipitation showed significant seasonal changes, lower in the winter and spring, higher in the summer and autumn;②The monthly average D-excess of Wuwei Station is lower than that of Xidahe Station. In addition to the possibility of different water vapor sources, the high-altitude mountain areas are more affected by local recirculating water vapor, and the secondary evaporation under the clouds in low-altitude plain areas is stronger;③The stable isotope of precipitation in the basin shows a significant temperature effect, and the precipitation effect is reflected on the weather scale, which may be affected by leaching or monsoon circulation;④The δ18O value of precipitation is negatively correlated with the average relative humidity. It may be that the secondary evaporation under the cloud is weakened by the increase of precipitation and humidity.