Role of Biological Measures in Soil Erosion Processes using InVEST Model in the Sharghong Watershed, South Khorasan, Iran

Ecosystems nowadays play a unique role in meeting human demands and offering a variety of services to their stakeholders. However, occurrence of various happening, including population increase and rising demand for basic human requirements, have created problems for Ecosystem Services (ES). As a result, land degradation is a significant environmental issue that is impacted by a variety of elements and factors. Soil conservation and erosion prevention can benefit from management and conservation measures, as well as the development of plant cover in a watershed. Therefore, an effort has been made in this study to assess how the Sharghong Watershed in Southern Khorasan, Iran, and its biological and management activities affect soil erosion at various rainfall intensities.

The Sharghong Watershed, with an area of 94.87 km2 , is located in Birjand Township, South Khorasan Province, Iran. The mean annual precipitation in the watershed is approximately 210 mm. Due to its steep slopes in the eastern and southeastern parts, the presence of residential areas and barberry orchards in the floodplain, and intense precipitation in the spring, the Sharghong Watershed has a good potential for flooding. for evaluating. The role of biological restoration operations in soil erosion processes in study watershed InVEST Model was used. Annual precipitation data from the Qaen, Birjand, Mousavieh, and Mansourabad stations were utilized for the period between 2002 and 2020, with return periods of 2, 5, 10, and 50 years, to generate the inputs for the InVEST model. The erosivity, erodibility, crop management and land maintenance factor were then determined.

The maximum rainfall erosivity index (R) values for return periods of 2, 5, 10, and 50 years were 47.08, 63.68, 85.01, and 98.94 MJ mm ha-1 h -1 , respectively. The minimum values of R for the same return periods were 42.88, 56.68, 74.47, and 85.85 MJ mm ha-1 h -1 , respectively. The annual sediment yield for return periods of 2, 5, 10, and 50 years were 6699.27, 9024.56, 17452.27, and 20862.30 t, respectively. Following the implementation of the management scenario in different sub-watersheds, sediment yield reached 6439.39, 8668.37, 16892.94, and 17390.87 t, respectively. The obtained results indicated reductions of 3.9, 3.9, 3.2, and 1.7%, respectively, for return periods of 2, 5, 10, and 50 years.

In this research, the role of biological management in controlling erosion and sedimentation in the Sharghonj Watershed during the different return periods of rainfall has been evaluated. The results of the research indicate that with the increase in the intensity of rainfall, in the current land use, the amount of erosion and sedimentation has increased, but with the application of management scenarios at the level of different sub-catchment, erosion and sedimentation has slightly decreased during the different return periods of rainfall. Due to the fact that the intensity of rainfall in the region plays an important role in creating erosion and its effect is intensified by the combination of sloping lands, the principled use of land in accordance with its potential can play an effective role in preventing land degradation. Therefore, the approaches of this research can be beneficial for providing a suitable management model for managers, operators and beneficiaries of watersheds.