Document Type : Complete scientific research article
Authors
1
Department of Rangeland and Watershed Management, Faculty of Natural Resources, University of Kurdistan, Sanandaj, Iran
2
Environmental Expert, Environmental Protection Department of Kurdistan Province, Sanandaj, Iran
Abstract
Abstract
Introduction and Objectives: Water infiltration into soil profile is one of the most important components of the water cycle, playing an essential role in determining the hydrological behavior of soil, the amount of runoff generation in a watershed, and the amount of soil moisture for the growth of vegetation and crops. Its variability is influenced by many factors such as precipitation characteristics, soil, vegetation type, land use, land slope and season of the year, which must be determined in each region because these characteristics are highly site-specific. Due to the lack of information on the variability of water infiltration into a soil on different parts of a slope, the aim of this research is to investigate the variability of infiltration in different parts of a slope in different seasons of the year.
Materials and Methods: In this research, a slope with a length of approximately 60 meters was selected inside the University of Kurdistan campus. Three points on this slope, including the upslope point with 0% slope, the middle slope point with 22% slope, and the downslope point with 28% slope, were considered for the establishment of double rings. The soil texture was clay and clay loam and the type of vegetation was sparse raneglands. Infiltration measurement at these three points was repeated three times in the three seasons of Fall, Winter and Spring with time intervals of one month. During the experiment, the initial soil moisture and the saturated moisture contents of the soil were measured by the gravimetric method. The collected data were analyzed in a randomized complete block design.
Results: The results showed that different slopes had no effect on the intensity of initial infiltration, the average intensity of infiltration and the intensity of final infiltration. The results also demonstrated that the initial ifiltration rate and the average infiltration rate in Fall were significantly different from those of Winter and Spring, while the final infiltration rate was the same in all seasons and its value was not affected by seasonal changes. Further investigations indicated that there is no significant relationship between initial infiltration intensity, average infiltration intensity and final infiltration intensity at three points of the slope and in three seasons of the year with initial soil moisture and soil saturation, which implies that the difference of infiltration intensities in different seasons cannot be justified with changes in initial moisture and soil saturation.
Discussion and Conclusion: It can be suggested that infiltration at any point is completely dependent on the characteristics of that point and it is not possible to generalize a specific behavior pattern of this component to other points. Therefore, it is necessary to measure the infiltration at each point and even during modeling, the natural characteristics of that point must be fully understood.
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