An experimental analysis of hydrodynamic behaviour on soils and hillslopes in a subtropical mountainous environment (Western Sierra Madre, Mexico)

Many soils parameters and features play a role in explaining the hydrodynamic behaviour of a watershed. Textural data are relatively easy to obtain and to spatialise, due to their low spatial variability. Inversely, structural features usually exhibit great spatial variability and thus, are difficult to interpolate and to integrate in the framework of a hydrologic model. However, structural characteristics of the soils seem to have a greater influence on catchment hydrological balance than the textural ones. The objectives of this study were to identify which parameters control the soil surface hydrological behaviour and quantify the magnitude of their spatial variability. Measurements of soils characteristics, including bulk density and hydraulic conductivity, were carried out in five watersheds in the Western Sierra Madre (Northern Mexico). It is shown in this study that on a natural grassland under subtropical mountainous climate, spatial variability of soil hydraulic conductivity is almost as high at a 1-m2 scale as at a 1-km2 one. The main discriminating variables which account for the spatial variability appeared to be the lithology and overall the soil surface features, both being related. The latter seems to be a synthetic indicator of basin hydrodynamic behaviour, and to be easier than others to spatialise.