Document Type : Original Article
Subjects
Soil is recognized as one of the most vital renewable resources globally. Currently, soil erosion has become a serious threat to human welfare and even the survival of humanity. This phenomenon is considered one of the fundamental environmental challenges for human societies. Global studies indicate that nearly 58% of degraded lands worldwide are caused by soil erosion, leading to a 17% reduction in agricultural production and significant environmental damage. Soil erosion is a key issue in natural resource conservation and watershed management research, influenced by natural and human factors. Therefore, understanding the intensity of soil erosion allows for identifying critical areas and prioritizing conservation measures. In this context, to mitigate the negative impacts of soil erosion, it is crucial to examine the factors influencing soil loss and accurately assess the extent of soil erosion to provide a correct evaluation of the current situation. Moreover, calculating the amount of soil erosion using various computational models and methods is feasible, and selecting the optimal method for measuring it is paramount. Various methods have been proposed worldwide to measure soil loss in different regions. Therefore, this study aims to evaluate the impact of biological conservation measures using the RUSLE model, based on remote sensing data, in the Chikan and Morzyan watersheds of Fars Province. By analyzing the effects of these measures, this research contributes significantly to the sustainable management of lands and the reduction of soil erosion-related damages.
The Chikan-Morzyan watershed is located 80 km north of Sepidan city in Fars Province, covering an area of 12,333 hectares. The watershed has a maximum elevation of 3,125 meters and a minimum elevation of 1,811 meters, with the highest annual precipitation reaching 571.2 mm and the lowest precipitation at 471.6 mm. This study used the RUSLE model based on remote sensing data to estimate soil erosion over 29 years at four-time intervals (1992, 2003, 2017, and 2021). To measure soil erosion, the RUSLE model guidelines were applied, and maps of erosivity (R), soil erodibility (K), topography (LS), vegetation cover (C), and conservation practices (P) were prepared for the watershed area. To assess the impact of watershed conservation measures, changes in the C factor were examined under the influence of biological conservation practices, assuming the other model factors remained constant throughout the study period. The amount of soil erosion was then estimated based on these changes.
The results of evaluating the impact of watershed management interventions in the studied watershed indicated that the values of the rainfall erosivity factor (R) in the watershed ranged from 31.5 to 488.42 MJmmha⁻¹h⁻¹y⁻¹, with a mean value of 224.98 and a standard deviation of 39.45 MJmmha⁻¹h⁻¹y⁻¹. The results of calculating the soil erodibility factor (K) in the study area revealed that the range of K values varied from 0.0129 to 0.0132. The highest erosion rates were observed in the southeast of the watershed, while the lowest values were found in the southern, central, eastern, western, and some northern parts of the watershed. The slope-length (LS) factor map showed that this factor ranged from 0.065 to 196.497 t ha h ha⁻¹MJ⁻¹mm⁻¹, with an average value of 6.89 t ha h ha⁻¹MJ⁻¹mm⁻¹ and a standard deviation of 8.12 t ha h ha⁻¹MJ⁻¹mm⁻¹.
The findings from the assessment of the changes in the cover management factor (C) indicated that the values of this factor for the years 1992, 2003, 2017, and 2021 varied between 0.19 and 1, 0.2 and 1, 0.21 and 0.99, and 0.21 and 1, respectively. Moreover, the annual average soil erosion in the Chikan and Morzian watershed, under the influence of watershed management practices, showed a relatively decreasing trend over the years, with values of 16.88, 16.32, 15.41, and 15.08 tons per hectare, respectively.
The findings of this study indicate that the implementation of biological measures during the study period has had a positive impact on reducing soil erosion in the Chikan and Morzian watershed. Results from the RUSLE model and the analysis of changes in the C-factor show a reduction in soil erosion over the years. This reduction in soil erosion is primarily attributed to the improvement in vegetation cover and soil structure enhancement resulting from the biological measures. In conclusion, biological measures, such as afforestation and vegetation restoration, can serve as an effective and sustainable solution for reducing soil erosion in vulnerable and degraded watersheds. These methods not only contribute to the reduction of erosion but also can be considered valuable tools in natural resource management. In addition to their positive effects on soil erosion reduction, these measures also offer additional benefits, such as increased forage production, reduced runoff, enhanced soil moisture retention, improved biodiversity, and even an increase in recreational and ecotourism values in the region. Therefore, it is recommended that in different climatic conditions, the impact of biological measures on soil erosion and sedimentation should be evaluated using various models and methods. Such assessments can significantly influence optimal decision-making regarding watershed management, soil conservation, and water resource protection. Ultimately, further research in diverse regions, utilizing more accurate data, could enhance sustainable natural resource management strategies and strengthen biological conservation measures.
I would like to express my deepest gratitude and appreciation for the cooperation of the General Directorate of Natural Resources and Watershed Management of Fars Province, which assisted in carrying out various stages of the research, including providing data and vehicles for field visits.
The authors of this article declare that they have no conflicts of interest with regard to the writing and publication of the materials and results of this research.
