Journal of Watershed Management Research

Extended Abstract
Background: The increasing loss of water and soil resources has intensified over the past few decades due to human and sometimes climatic factors and has led to many economic and social consequences. In addition to creating economic costs and losses of national capital, this issue has led to an increase in the occurrence of floods, an increase in the rate of sediment production, a decrease in the useful life of dam reservoirs, the loss of vegetation cover, and a decrease in agricultural production, as well as water scarcity. Proper management of Iran's watersheds is one of the most important methods for using water and soil resources, which requires comprehensive and complete information on different administrative and management methods. Watershed management projects are large-scale and long-term projects that can widely affect the entire basin. Since such projects may have undesirable or desirable consequences, it is necessary to have dynamic planning and strategies. In fact, watershed management should follow an adaptive management approach that includes monitoring, evaluation, feedback, and necessary adjustments. The issue of monitoring and evaluation is one of the basic pillars of implementing watershed management projects, which is considered a tool to examine their effectiveness. Since the success of watershed management projects depends on their multifunctional objectives at various technical, social, and political levels, achieving the objectives, monitoring, and evaluation of watershed management projects is a necessary and inevitable task. Currently, most watershed management and development projects lack a monitoring and evaluation program on the performance and plans of the project. Definitely, monitoring and evaluation require quantitative data to show whether or not the work carried out is in line with the project objectives and how much deviation there is from the main objectives. Therefore, monitoring and evaluation at each stage of the project, comparing, selecting or rejecting existing options, making decisions, dividing tasks, making adjustments, and making necessary judgments and decisions show that the existence of a monitoring and evaluation system during project implementation is very necessary and essential. Therefore, evaluating the performance of watershed management measures in terms of economic aspects makes it possible to determine the type and extent of the project's effects and the affecting factors, and provide necessary guidelines for the optimal implementation of these plans to officials and planners in the future. Therefore, it is necessary to study the impact of these projects in reducing damage to natural resources and preventing accidents in the country's watersheds, as well as the economic and livelihood consequences of watershed management measures from the perspective of people living in villages bordering the project and experts. This is to determine the positive performance and the extent of implementing such projects in controlling and improving the conditions of the intended watershed. This research aims to evaluate the effect of watershed management measures before and after a project implementation on the general condition of the Langar 1 watershed, which has been examined throughout the article.
Methods: The effectiveness of watershed projects implemented by considering factors, such as erosion and sedimentation, change of use, peak discharge, flood volume, economic issues of watershed residents, and vegetation changes before and after the implementation of these projects (between 2009 and 2021), was monitored and evaluated using satellite images, field visits, and receiving data from the General Department of Natural Resources of Mazandaran Province, Sari, in the Langar 1 watershed of Mazandaran Province.
Results: The implementation of biological and mechanical operations in the entire basin caused 17.89 and 25.94 percent reductions in erosion and sedimentation rates, a 30 percent increase in the dense vegetation index, a 1178.18 million cubic meter reduction in the flood volume, and an increase in the profit rate at a cost of 1/12 for the watershed dwellers. Therefore, it is suggested to expand the implementation of biological and mechanical operations in accordance with the cultivation pattern and socioeconomic issues at the basin level.
Conclusion: The results of the study show that the watershed management measures carried out in the Langar 1 watershed have significantly ingluenced improving the quantitative and qualitative characteristics of vegetation cover and meeting the project objectives. The implementation of watershed management plans is beneficial, economically justified, increases groundwater, and is effective in reducing erosion and sedimentation, which has resulted in an 18% reduction in the rate of erosion and sedimentation in the entire basin compared to 2009. A comparison of specific erosion and sedimentation before and after the implementation of watershed management operations shows that the rate of specific erosion and sedimentation has decreased as a result of the implementation of various watershed management measures (biological and managerial). Sub-basins that contained barren lands in 2009 turned into sparse and dense vegetation in 2011, and their percentage reached zero, indicating the effect of watershed management measures, which include implementing biological operations (planting seedlings and trees) and mechanical operations in the Langar 1 basin. The peak discharge and flood volume in the Langar 1 basin show that the concentration time has increased during the statistical period, and the other mentioned parameters have had a decreasing trend, which, along with the increase in changes in the NDVI vegetation index in the Langar 1 basin, further demonstrates the positive effect of watershed management measures. In spite to the limitations of this research, such as incomplete basin information, failure to consider the study budget, failure to utilize diverse scientific expertise, and the weakness of the agricultural extension sector to increase agricultural, livestock, and horticultural production, conservation planning and economic management can be carried out based on the needs and production capabilities of each watershed. Therefore, watershed management measures in the basins are suggested to be based on considering economic issues and implementing integrated plans, so that the income of the residents can be increased, in addition to protecting the lands.