Comprehensive Estimation of Erosion and Sediment Components using IntErO Model in the KoozehTopraghi Watershed, Ardabil Province

Soil erosion is one of the most important environmental issues that causes various ecological, social and economic problems. Today, the use of various models for estimating and predicting hydrological data of watersheds is increasing. Soil erosion risk assessment is a special form of land resources evaluation, and its purpose is to divide the land into small areas based on the type of erosion and its amount, which is essential in the soil conservation planning. Developing comprehensive soil erosion models applicable in different environmental conditions is highly important. The Intensity of Erosion and Outflow (IntErO) model is a new graphical model that has a user-friendly software and could present a comprehensive view from watershed erosional components. Awareness of important coefficients such as watershed development, river basin tortuousness, erosion energy of the basin's relief, the region's permeability, vegetation cover, and deposit retention coefficients that provided by IntErO model has a key role to adapt proper watershed management and conservative measures, particularly the best management practices (BMPs) that are currently considered by policymakers and executive managers.

Due to the positive reports on the proper efficiency of the IntErO model in some parts of the areas such as Bosnia & Herzegovina, Bulgaria, Croatia, Czech Republic, Italy, Brazil, and recently in North Khorasan and Kurdistan provinces, the present study was conducted with the aim of obtaining comprehensive information on the erosional characteristics of the KoozehTopraghi Watershed located in the southern part of Ardabil Province. The studied watershed with an area of 801.40 km2 was divided into 36 sub-watersheds according to topographical and hydrological properties. Totally, the IntErO program package for estimating soil erosion and sediment yield components uses 26 input data including geometric, topographic, maximum outflow, hydrological and soil erosion intensity properties. All primary maps for total watershed and its 36 sub-watersheds were processed and provided in the ArcGIS 10.6 environment. Then, according to the required standards of the model, the data bank was provided in the Excel 2016 environment and accordingly uploaded to the IntErO software. Finally, after running the IntErO model, 22 components related to the soil erosion process of KoozehTopraghi Watershed were obtained.

According to the results of the IntErO model, the spatial variability was confirmed in relation to the most of erosional components through 36 sub-watersheds which indicate the diversity of ecological and biophysical conditions at the whole watershed. In general, the maximum and minimum ​​of soil erosion coefficient (Z) were estimated in the sub-watersheds 6 and 10, respectively. According to the obtained results, most of the study sub-watersheds have experienced severe erosion. It was also found that the mean of the production of erosion material in the river basin (Wgod) was equal to 222854.65 m3 y-1, respectively whereby it’s minimum and maximum were obtained in the sub-watersheds 6 and 33, respectively. The reason for the high amount of specific sediment yield in some sub-watersheds can be attributed to their severe exploitation for human needs and consequently severe erosion. The results also showed that the mean value and standard deviation of the coefficient of the deposit retention (Ru) for the whole watershed was 0.26 ± 0.09. The values ​​of real soil loss (Ggod) and specific real soil loss (Ggod/km2) were evaluated as 172704.90 m3 y-1 and 215.50 m3 km2 y-1. The results showed that there was a lot of permeability in the upland sub-watersheds. In these sub-watersheds, due to the existence of rangelands and higher vegetation cover, more water penetrates.

In general, the results showed that the erosion values ​​at the lowlands of the study watershed are much higher than at the highlands. The present results are consistent with the other researches that reported the high level of ecological sensitivity in the lowlands of ​​the KoozehTopraghi Watershed. The results of the present study can be used as a useful managerial tool in the field of sustainable agricultural production and optimal use of natural resources. Finally, it is recommended to compare the applicability of the IntErO model in different environmental conditions, considering its comprehensiveness in analyzing the erosional status. The results of this study, in addition to its capability for modeling different watershed ecological, hydrological and managerial processes, their analysis is useful to prioritize the critical regions as well as sustainable and effective implantation of restoration and conservative practices in the KoozehTopraghi Watershed.