Investigating the effect of edaphic parameters on runoff using a rainfall simulator

Considering arid and semiarid climatic conditions in Iran، the runoff generated from rainfall is one of the main sources of water supply demands for agricultural، industrial and domestic uses. Depending upon watersheds’ characteristics and weather conditions، a substantial part of precipitation may be changed into runoff. The knowledge about the discharge and volume of the runoff generated by rainfalls، especially in unguaged catchments، plays an important role in water resources management planning. In the absence of sufficient data recorded from the real events، use of rainfall simulators in the field and laboratory may be recommended to simulate runoff generation process in different conditions of soils، vegetation cover، slope and rainfalls. In this research، a rainfall simulator was used to investigate the effect of vegetation cover density and soil moisture on runoff values. During this study، the rainfalls with intensities of 24. 5 and 32 mm/h on 145 experimental plots in Taleghan basin were generated and the respective amounts of runoff were measured. Based on the obtained results، correlation matrix confirmed the visual interpretation of the dissipation graphs achieved from the investigated independent and dependent variables. The vegetation cover density was found the most effective variable، affecting the runoff discharge in the two simulated rainfall intensities. Percentage of vegetation cover in rainfall intensities of 24. 5 and 32 mm/h was correlated with runoff value with the coefficients of -0. 903 and 0. 872، respectively at significant level of 0. 01. The two regression relations were also developed for predicting runoff values in different conditions in the range of investigated independent variables.