祁连山北坡稳定同位素生态水文学研究的初步进展与成果应用

2012年以来祁连山北坡稳定同位素生态水文学研究的初步进展包括:(1)云下蒸发和水汽再循环是降水稳定同位素演化的重要因子;(2)各水体稳定同位素年内变化指示了地表水和地下水的不同转化模态;(3)海拔2000 m以上山区水汽再循环贡献了约24%的降水;(4)冰雪冻土带贡献了出山径流的80%左右。上述结果为祁连山国家公园范围区划和生态保护提供了科技支撑。

Ecohydrology based on stable isotope tracing in the northern Qilian Mountains: preliminary progress and its applications

This study has analyzed preliminary progress in the study of stable isotope ecohydrology based on systematic observation and continuous sampling in the northern slopes of the Qilian Mountains since 2012. The results showed that:sub-cloud evaporation and water vapor recycling are important for the evolution mechanisms of stable isotope of precipitation in the study area. When precipitation is higher, sub-cloud evaporation of falling raindrops will be lower and enrichment of δ¹⁸O is weaker. Therefore, rainfall events with higher precipitation amounts had more depleted δ¹⁸O and vice versa. The stable isotope of river and groundwater is stable within the year, contrast with the significant annual fluctuation in precipitation stable isotopes, which reflects the transformation from snow melt water to groundwater in glacier terminus, from supra-permafrost water to surface water in permafrost regions, and repeated transformation of surface water and groundwater in vegetation zone. Under the background of climate warming, with the intensification of evapotranspiration in alpine regions, water vapor recycling is gradually accelerating, which becomes the main transformation from gaseous water to liquid water. Meanwhile, it is an important component of water vapor source for regional precipitation. Water vapor recycling contributes about 24% of precipitation in mountainous regions above 2 000 m a.s.l. About 4/5 of the runoff is recharged in the cryosphere belt above 3 600 m a.s.l. in the northern slopes of the Qilian Mountains. The contribution of atmospheric precipitation, supra-permafrost water and glacier and snow meltwater to runoff in the outlet is 70%, 22% and 8%, respectively. The Qilian Mountains National Park is located in 95°-103.5°E, 36.8°-39.6°N, with a total area of 4.8×10⁴ km² (accounting for 27% of the total area of the Qilian Mountains). This result has clarified the hydrological process indicated by stable isotopes in the inland river basins under the background of climate warming and intense cryosphere ablation, provided a new basis to measure the strengthening of water vapor recycling in alpine regions, quantified the contribution ratio of water vapor recycling precipitation, and proved the fact that the contribution ratio of cryospheric meltwater to runoff variations. In particular, it has provided scientific support and technical guidance for establishing the Qilian Mountains National Park.