Responses of soil water retention to climate and underlying condition changes in river source areas: A case study of the Hei River basin and Bai River basin, China

Abstract

In the context of global warming, the soil water retention (SWR) functions of river basins in river source areas dominating alpine-cold ecosystems are changing. Quantifying spatiotemporal dynamics of SWR in the area is fundamental for better understanding the climatic and underlying regulation on water formation and benefitting the reasonable management of basin resources. In this study, the Hei River basin (HRB) and the Bai River basin (BRB), located in the upper reaches of the China’s Yellow River, were employed as the study area. SWR across the two basins was estimated by using the water yield module of the InVEST model; the sensitive responses of SWR to changes of climate and underlying conditions were quantitatively assessed during the time period from 1981 to 2015. The total SWR was quantified into multiyearly averaged annual values of 1.61 × 10⁸ m³ in the HRB and 1.75 × 10⁸ m³ in the BRB. SWR in the two river basins had decreased consistently during the statistic period, especially in the midstream regions of the two basins in the 1980s. The positive effects of air temperature, precipitation, and the normalized difference vegetation index (NDVI) were evidenced in the study area, while the negative effect of potential evapotranspiration (PET) was found. Comparatively, precipitation and PET had more significant influences on SWR than the other two factors. The study could be considered as a case example for better understanding regional SWR dynamics together with its responses to environmental changes in the alpine-cold river source areas.