Development and Application of Single-Parameter Soil Water Diffusivity Models for the Nanxiaohegou Basin

Predicting soil water movement and the transport of pollutants requires a good understanding of soil hydraulic properties. One of the most important hydraulic properties of unsaturated soil is the soil water diffusivity. However, because this parameter exhibits significant spatial variation, monitoring the soil water diffusivity over a large area of land would require the acquisition of an impractically large number of measurements in order to avoid introducing significant errors. To address this issue, the soil water diffusivity was measured in 56 soil samples gathered from across the Nanxiaohegou basin. These experimental data were then used to derive single- and double-logarithmic models for predicting the soil moisture diffusivity for the basin as a whole and for specific soil and terrain types within the basin. A linear relationship was observed between the two parameters of the single-logarithmic model, making it possible to establish a third series of single-parameter models. All three model types yielded estimates that were in good agreement with the experimental results. In addition, analyses of the single-parameter models revealed that the parameter varied according to the nature of the sampled soil and terrain, suggesting that it may provide useful information about the spatial variation of the soil moisture diffusivity.