Estimation of surface soil moisture content using fractals.

Soil moisture content is a key factor affecting surface evaporation in the hydrologic cycle, with application in water resources management, early drought warning system, irrigation management, and estimation of crop yield. The subject of soil moisture content has long been of interest in hydrology, agriculture, forestry, and soil mechanics engineering. The cracking of surface soil due to dryness is often used to describe the drought condition of the land based on the certain relationship between soil cracking and moisture content. This study establishes the relation between fractal dimensions of soil cracking patterns and moisture content of surface soil. Sixteen soil samples were prepared and subjected to drying under different temperature levels to crack in the laboratory. Photographs of the cracks were digitized and an algorithm for calculating fractal dimensions of cracking patterns was developed. The results demonstrated that the fractal dimensions of cracking patterns are highly correlated with the surface soil moisture content; the lower the soil moisture content, the larger the fractal dimension is. Therefore, the surface soil moisture content-fractal dimension (D-w) rating curves can be established. Once crack structures occur on surface soil, the moisture content of the surface soil can be estimated quickly and accurately by mean of remote sensing technique such as UAV together with the fractal analysis.