Soil water sources and transport modes based on stable isotope tracing in Northeastern Qinghai-Tibet Plateau
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Graphical Abstract
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Abstract
A thorough understanding of the source and infiltration mechanism of soil water is of great significance to the stable supply of regional water resources and the protection of ecological environment. To solve this crucial scientific problem, a total of 1980 samples of various water bodies in Qilian Mountains were collected in early, heavy and end ablation period in 2012-2019 to determine the source of soil water with endmember mixing analysis. Double isotope mass balance was used to calculate the relative contribution of piston flow and preferred flow to groundwater. The results of the study show that precipitation dominated the soil water in the study region, and it contributes 78%, 89% and 91% of soil water in early, heavy and end ablation periods, respectively. Ground ice meltwater is also an important source of soil water, its contribution was 16%, 11% and 7% in early, heavy and end ablation period, respectively. Snowmelt contributed to soil water only during the early (6%) and late (2%) ablation periods. Groundwater is replenished through the combined effects of preferential flow and piston flow. According to double isotope mass balance, the contribution of priority flow to shallow groundwater is 34%, 45% and 34%, respectively in early, heavy and end ablation periods. This study identified the sources of soil water and water transport mechanisms in the Qilian Mountains, providing scientific and technological support for water resource conservation and sustainable utilization in cold regions.
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