Fractal Behavior of Soil Water Storage At Multiple Depths.

Knowledge on the spatio-temporal behavior of soil water has important hydrologic applications. Data intensive measurement of surface soil water using remote sensing has established that the spatial variability of soil water can be described using the principle of self similarity (scaling properties). This information can be used in deciding land management practices provided the relationship holds at deep layer. This study examines the scaling properties of soil water below the soil surface using intensive sampling, thereby allowing the information to be available to the plant root and vadose zone models. Soil water storage down to 1.4 m depth at seven equal intervals was measured along a transect of 576 m for 5 years. The surface soil water storage showed multifractal nature only during the wet period indicating the need of multiple scaling indices in transferring soil water variability information over multiple scales. However, with increasing depth, the soil water storage became monofractal in nature indicating the need of single scaling index to upscale/downscale soil water variability information. The dynamic nature made the surface layer soil water highly variable compared to the deep layers in wet period. On contrary to the wet period, all soil layers during the dry period were monofractal in nature may be due to the high evapotranspirative demand of the growing vegetation. Strong similarity between the scaling properties at the surface layer and deep layers provides the possibility of inferring about the whole profile soil water dynamics using the scaling properties of the easy-to-measure surface soil water storage data.