Knowing the water retention properties of soil can help with predicting water infltration into the soil, the potential for runof generation and sediment yield, and ultimately, better management of natural areas. The purpose of this study was to investigate the characteristics of the soil water retention curve (SWRC) and its efects on infltration rate and runof generation. For this purpose, an arid area in eastern Iran for which rainfall and runof data were available was selected. Two variables that are assumed to afect soil water retention and runof generation were used in this study, namely geological formation and topographic wetness index (TWI). The geological formations layer for the study area was extracted from 1:100,000 geological maps, and TWI was derived from the combination of slope and the area of upstream basins. Initial infltration rate, stable infltration rate, and time to stable infltration rate were determined using the double ring infltration apparatus and were used to create the soil infltration potential curve (SIPC). In addition, saturation soil water content, feld capacity, permanent wilting point, plant available water, and area under the curve were determined using pressure plates, and were used to create SWRC. The results showed that the characteristics of SWRC, SIPC, and soil water conditions after rainfall are afected by geological formation and TWI. All characteristics of SWRC were higher in the shale formation than the sandstone formation, and areas with higher TWI had lower soil water retention. Also, soils in the sandstone formation had higher initial and stable infltration rates and required a shorter time to reach stable infltration rates. The results showed that conversion of the soil water curve from the soil water-suction mode to the suction-time mode allows for predicting post-rainfall soil water conditions. Finally, areas in the shale formation with maximum TWI had the highest water retention potential, lowest infltration rates, and maximum runof generation capacity

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