Evaluation of temporal-spatial variations of soil moisture balance by Thorenthwaite Matter method (Case study: Behesht Abad basin)

For the sustainable management of water resources, it is necessary to determine the water balance and its components for the correct use of water. In this study, to obtain a general overview of the water balance and its components, the soil moisture balance was calculated using the Thorenthwaite Matter model in the Behesht Abad basin during 2003-2015. Distribution maps, including rainfall, temperature, actual and potential evapotranspiration, soil moisture, infiltration, surface runoff and leaf area index were prepared. The results showed that in spatial distribution, in spring and summer, the highest (8.98 mm) and the lowest runoff occurs at the altitudes and in the basin outlet, and in autumn and winter, the highest (46.72 mm) and the lowest runoff occurs at the outlet and in the altitudes, respectively. The correlation coefficient between observed and simulated surface runoff is 53%. The amount of infiltration decreases during dry months, the highest infiltration (range from 16 to 31 mm) has occurred in the range of sandy loam and clay loam textures and in agricultural areas and rangeland with good and medium coverage. In terms of spatial distribution, agriculture land and good and medium rangeland have more actual evapotranspiration, which often consistent with regions have the highest leaf area index. In general, the results of this research can be useful in identifying the soil moisture condition and various aspects of this complex system and also watershed management.