EN
The knowledge of soil moisture spatial variability is an important issue for hydrological and climatic studies. The purpose of this study was to evaluate the spatial distribution of soil water resources in a lowland basin. The area chosen for study is the Liwiec basin (left tributary of the Bug river), situated in central Poland. The analysis is based on field measurements of volumetric soil moisture conducted since 2009 till 2011. Soil moisture measurements were performed at six locations in the Liwiec basin. The measurements were carried out using a portable time domain reflectometer (TDR). Empirical soil moisture data was used to verify the hypothesis of temporal stability of soil moisture. The concept of temporal stability proposed in pedohydrology in the 80s of the twentieth century by G. Vachaud et al. (1985), presupposes the existence of the relationship between the soil moisture indicators at a point and the values representing the spatial averages. Assuming temporal stability of soil moisture in the Liwiec basin a method of evaluation of soil moisture spatial distribution has been developed based on field measurements and spatial data (i.e. DEM, digital agricultural soil map, forest digital map). Parameterization of the factors influencing the variability of soil moisture (topography, particie size distribution of soils and density of vegetation) was made based on the topographic wetness index (TWI). The modified TWI index was considered a static model of the spatial structure of soil moisture in the Liwiec basin. By integrating this spatial model and the results of field measurements, soil moisture maps were developed.