Spatio‐temporal variability of multi‐layer soil water at a hillslope scale in the critical zone of the Chinese Loess Plateau

Abstract

AbstractUnderstanding the spatio‐temporal variability of soil water content (SWC) in the Critical Zone (CZ) is essential to balance plant‐water benefits and to enhance the ability to monitor and predict drought. In current study, the spatial variability and temporal stability of multi‐layer SWC to a depth of 500 cm (35 soil layers) at 27 sampling sites were evaluated at a hillslope scale. A total of 64 SWC measurements were obtained from 28 March, 2017 to 23 December, 2018. We hypothesized the existence of a “special point” that is temporally stable both in horizontal direction (which means different layers) and in vertical direction (which means different profiles). We found a clear seasonal dynamic pattern of mean SWC for all sites in the 0–500 cm profile, with SWC varying from 4.0 to 24.8%. In the horizontal layer, both the 130‐cm and 140‐cm layers contained a maximum number of temporal stability sites (N = 4) which all located at H11, H13, H14 and H26. In the vertical profile, H19 was the most stable site, followed by H10 and H26, with 15, 10 and 6 stable layers, respectively. The decreasing order of SWC temporal stability was 200–500 cm, 0–500 cm and 0–200 cm, which means the temporal stability of SWC in 0–500 cm profile was more dependent on the 0–200 cm sub‐profile. At a three‐dimension scale, the most temporal stability layer and site was 180‐cm of H1 and H21 of 220‐cm, which confirmed our hypothesis. This study provides an accurate description of SWC spatio‐temporal variation at the hillslope scale, which is helpful for addressing eco‐hydrological models and water management issues in the Earth's CZs.