Spatial and Temporal Characteristics of Soil Moisture at Field Scale in an Arid Region of Northwest China

The knowledge of soil moisture spatial and temporal variability improves the understanding of the scale issue for hydrological and climatic studies. In the paper, daily soil moisture samplings at 144 locations were collected in the spring wheat region, and the classical statistics, geostatistics and time stability analysis were used together to discuss the temporal and spatial variability of soil moisture. The results showed that the dynamics variety of soil moisture decreased continually from surface soil to deep soil. And a linear descending relationship between the mean value and the coefficient of variation (i.e. CV) became evident. Basing on the geostatistics method, the spatial structure of soil moisture at wet condition was much stronger than that at dry condition. Time stability analysis showed there was a high time stability of soil moisture for different soil depths in the spring wheat region. So the appropriately selected five sampling points could provide accurate predictions of the field mean with low variability and small bias.