CATCHMENT-SCALE SPATIAL VARIABILITY ANALYSIS OF SOIL HYDRO-PHYSICAL PROPERTIES IN A SEMI-ARID REGION OF IRAN

Soil hydrau-physical data are important for many hydrological modelings. They are the main variables controlling the key processes such as water and chemicals movement and transport in the soil profiles. This study was conducted in order to analyze the spatial distribution of selected soil hydrau-physcial characteristics including infiltration rate (IR), saturated hydraulic conductivity (Ks), bulk density (BD), clay, silt, and sand content. The study area was sampled on a pseudo-regular sampling scheme with initial grid spacing of 1 km during June and July 2007. Maximum coefficient of variation (CV) was found for IR (72%) and Ks (67%). While, BD showed a minimum CV of 9%. Statistical analyses illustrated that there is a significant difference (P<0.05) in the mean values of IR in two different landforms, i.e., plateaus and alluvial plains. However, different land uses including rangelands and dry farming revealed no significant differences in the mean values of measured IR. The contrasting results were obtained for Ks. Geostatistical analyses revealed that the spatially dependent stochastic component (structure) was predominant over the nugget variance (noise). The developed and modeled variograms of each variable were used in generating kriged maps. As expected, these maps exploited spatial similarities among soil properties.