University of Tehran Press Journal of Ecohydrology 2423-6098 11 4 2024 12 21 Simulation of soil organic carbon losses in rangeland ecosystems using SWAT model (Case study: Yalfan Basin - Hamedan Province) Simulation of soil organic carbon losses in rangeland ecosystems using SWAT model (Case study: Yalfan Basin - Hamedan Province) 427 456 99582 10.22059/ije.2024.380588.1838 FA Mahnaz Norozi Nasir Msc. Graduate Sturdent, Department of Nature Engineering, Faculty of Natural Resources and Environment, Malayer University, Malayer, Iran Behnaz Attaeian Corresponding Author, Assistant Professor, Department of Natural Engineering, Faculty of Natural Resources and Environment, Malayer University, Malayer, Iran Behnoush Farokhzadeh Assistant Professor, Department of Nature Engineering, Faculty of Natural Resources and Environment, Malayer University, Malayer, Iran Mojgan Sadat Azimi Associate Professor of Rangeland Management, Rangeland Management Department, Faculty of Rangeland and Watershed Management, Gorgan University of Agriculture Sciences and Natural Resources, Gorgan, Iran Journal Article 2024 09 23 <strong>Objective</strong>: Rangelands are considered as a major carbon (C) sink to mitigate global climate change, However, ongoing disturbance from overgrazing, water erosion, land use changes, vegetation loss and soil surface degradation accelerate soil organic carbon loss in rangelands. Therefore, monitoring soil organic carbon loss in rangelands is important for integrated watershed management. This study aimed to estimate soil organic carbon loss using SWAT model in Yalfan watershed, Hamadan.<br /><strong>Method</strong>: For this purpose, water and suspended sediment (SS) samples were monthly collected from Yalfan river during April 2014 to April 2015 using depth-integrating sampling technique; and then samples were proceeded in the laboratory for particulate organic carbon (POC) analysis.<br /><strong>Results</strong>: The field assessment showed average of 26/35 ton/month of organic carbon loss during the study period in 2014-2015. While, the results showed no significant changes of monthly losses of particulate organic carbon (p>0.05) during 11-month sampling, However, the linear regression analysis provided a strong empirical model to predict soil POC loss based on sediment samples (R²= 0.97). Besides the empirical model, SWAT model was also calibrated and validated for discharge and sediment transport estimation. The simulation of particulate organic carbon loss was successfully developed based on SWAT model and empirical model for a period of 13 years (2002-2014). The total amount of POC loss simulated 3227/11 mg was that less than observed value predicted. In general, based on the statistics and charts indicators used can be acceptable simulation model is showed.<br /><strong>Conclusions</strong>: In general, according to the available data, the loss of particulate organic carbon is almost equal to 22.8% of sediment transport <strong>Objective</strong>: Rangelands are considered as a major carbon (C) sink to mitigate global climate change, However, ongoing disturbance from overgrazing, water erosion, land use changes, vegetation loss and soil surface degradation accelerate soil organic carbon loss in rangelands. Therefore, monitoring soil organic carbon loss in rangelands is important for integrated watershed management. This study aimed to estimate soil organic carbon loss using SWAT model in Yalfan watershed, Hamadan.<br /><strong>Method</strong>: For this purpose, water and suspended sediment (SS) samples were monthly collected from Yalfan river during April 2014 to April 2015 using depth-integrating sampling technique; and then samples were proceeded in the laboratory for particulate organic carbon (POC) analysis.<br /><strong>Results</strong>: The field assessment showed average of 26/35 ton/month of organic carbon loss during the study period in 2014-2015. While, the results showed no significant changes of monthly losses of particulate organic carbon (p>0.05) during 11-month sampling, However, the linear regression analysis provided a strong empirical model to predict soil POC loss based on sediment samples (R²= 0.97). Besides the empirical model, SWAT model was also calibrated and validated for discharge and sediment transport estimation. The simulation of particulate organic carbon loss was successfully developed based on SWAT model and empirical model for a period of 13 years (2002-2014). The total amount of POC loss simulated 3227/11 mg was that less than observed value predicted. In general, based on the statistics and charts indicators used can be acceptable simulation model is showed.<br /><strong>Conclusions</strong>: In general, according to the available data, the loss of particulate organic carbon is almost equal to 22.8% of sediment transport https://ije.ut.ac.ir/article_99582_f6d0ccc75b11cb4cc78be8a7094658c3.pdf