Soil water spatial distribution in dam farmland on the Loess Plateau, China

Abstract

On the Loess Plateau of China, lots of check-dams were constructed originally for sediment management. Simultaneously, these artificial projects can change the hydrological cycle in the form of collecting runoff and conserving water. An understanding of soil water spatial distribution in dam farmland is crucial for water resource management as well as the layout of check-dams construction. In this study, soil water spatial distribution in a selected dam farmland was analyzed by taking 2288 soil samples in autumn and spring, respectively. The results showed that the soil water contents presented obvious stratification characteristics along the soil profiles. From the back position to the front position along the alluvial direction, the mean soil water content and its variability showed by coefficient of variation (CV) increased. For different transects, semivariograms of soil water content of 0–150 cm can be generally well fitted by Gaussian model except for transect 9, which behaved the deepest soil layer and the nearest away from the dam body. Geostatistical analysis showed that from back position to front position, not only nugget variance but also structural variance increased but for correlation length, it decreased. These changes of spatial structure were believed to be associated with the sedimentation deposition characteristics along the alluvial direction. Soil water content with depth generally showed moderate spatial dependency. Compared with autumn, the soil water content in spring was significantly lower. The magnitude of variability in autumn was generally somewhat larger than in spring. For correlation length, however, it was a little smaller in autumn than in spring.