Iranian Jornal of Watershed Management Science&Engineering

fa ارزیابی مدلSEBS در تخمین تبخیر و تعرق واقعی با تأکید بر مدیریت پایدار منابع آب دشت چنداب تهران Evaluating the Efficiency of the SEBS Model in Estimating Actual Evapotranspiration: Emphasizing the Role of Flood Spreading in Sustainable Water Resources Management in the Chandab Plain, Tehran تخصصي Special پژوهشي Research مدیریت منابع آب در مناطق خشک و نیمه‌خشک همواره به دلیل بارندگی محدود و افزایش تقاضا برای آب با چالش‌های اساسی مواجه بوده است. در این مناطق، برآورد دقیق تبخیر و تعرق واقعی (ETa) نقش حیاتی در برنامه‌ریزی و مدیریت بهینه منابع آب، تخصیص آب در بخش‌های مختلف و مقابله با خشکسالی ایفا می‌کند. هدف اصلی این پژوهش، کالیبراسیون و اعتبارسنجی مدل SEBS برای برآورد تبخیر و تعرق واقعی در دشت چنـداب تهران و بررسی تأثیر پخش سیلاب بر توزیع مکانی تبخیر و تعرق است. مدل SEBS که بر اساس توازن انرژی سطح عمل می‌کند، از داده‌های ماهواره‌ای و هواشناسی برای محاسبه شار گرمای محسوس، گرمای نهان، شار گرمای خاک و تابش خالص بهره می‌برد. در این پژوهش از تصاویر ماهواره‌ای Landsat 8 و داده‌های هواشناسی مانند دما، رطوبت، سرعت باد و تابش خورشیدی، به‌همراه داده‌های رطوبت خاک از ایستگاه‌های زمینی استفاده شده است. برای کالیبراسیون مدل، از الگوریتم ژنتیک بهره گرفته شد تا تطابق بین خروجی مدل و داده‌های زمینی به حداکثر برسد. نتایج نشان داد که مدل SEBS پس از کالیبراسیون دقیق، توانایی بالایی در برآورد تبخیر و تعرق واقعی دارد. همچنین مقایسه بین نواحی تحت تأثیر پخش سیلاب و نواحی شاهد نشان داد که پخش سیلاب به‌طور میانگین باعث کاهش ۱۵ درصدی تبخیر و تعرق واقعی می‌شود. این کاهش به دلیل افزایش رطوبت خاک، بهبود وضعیت فیزیولوژیکی گیاهان و کاهش تنش آبی حاصل شده است. یافته‌ها نشان می‌دهد که پخش سیلاب می‌تواند راهکاری مؤثر برای افزایش ذخایر آب زیرزمینی، حفظ رطوبت خاک و ارتقای پایداری زیست‌محیطی در مناطق خشک و نیمه‌خشک باشد.   Abstract Abstract Introduction Water resource management in arid and semi-arid regions has consistently posed a fundamental challenge due to limited precipitation and increasing demand. In these regions, the accurate estimation of actual evapotranspiration (ETa) plays a crucial role in the planning and optimal management of water resources, the allocation of water to various sectors (agriculture, industry, potable water), and drought management. Evapotranspiration is a complex process influenced by many factors, including climatic conditions, soil characteristics, vegetation type, and land management practices. Various models have been developed to estimate actual evapotranspiration. Ground-based models, such as lysimeter and heat flux measurements, are accurate but require expensive equipment and specialized personnel, and are typically limited to local scales. Conversely, satellite-based models offer the potential to estimate evapotranspiration on a broad scale and at a lower cost. The Surface Energy Balance System (SEBS) model is a widely used model for estimating actual evapotranspiration that operates based on the surface energy balance. Utilizing satellite and meteorological data, this model calculates sensible heat flux, latent heat flux (evapotranspiration), soil heat flux, and net radiation. The primary objective of this research is to calibrate and validate the SEBS model in the Chandab Plain of Tehran and to analyze the effects of flood spreading on the spatial distribution of evapotranspiration which is located in an arid and semi-arid region, the Chandab Plain faces water scarcity challenges. Evaluating the effects of flood spreading on evapotranspiration can contribute to a better understanding of the impacts of this method on water resource management in the region. Materials and Methods The study area for this research is the Chandab Plain, located in the southeastern part of Tehran. To implement the SEBS model, several datasets were utilized. Landsat 8 satellite imagery, with a spatial resolution of 30 meters, was downloaded from the United States Geological Survey (USGS) website. Prior to analysis, the imagery underwent essential pre-processing steps, including geometric and atmospheric corrections, to ensure data quality. Additionally, meteorological data—such as temperature, humidity, wind speed, and solar radiation—were gathered from synoptic meteorological stations situated near the study area. These meteorological variables provided the necessary inputs for the SEBS model. Ground-based measurements, particularly soil moisture data collected from various locations within the Chandab Plain, were also employed to calibrate the model and evaluate its accuracy. The SEBS model was implemented using the aforementioned data. A genetic algorithm-based optimization method was employed for model calibration. In this method, the various parameters of the SEBS model were adjusted to maximize the agreement between the model output and the ground-based soil moisture data. Following model calibration, actual evapotranspiration was calculated for the entire study area using the calibrated model. To evaluate the effects of flood spreading, areas affected by flood spreading were identified using satellite imagery and field visits. Subsequently, maps of evapotranspiration in flood-affected and unaffected areas were compared. The accuracy of the SEBS model was assessed using statistical indices, including the coefficient of determination (R²) and the mean absolute error (MAE). Results and Discussion The findings of this research demonstrated that the SEBS model, when subjected to precise calibration, exhibits a strong capability for accurately estimating actual evapotranspiration in the Chahdabab Plain of Tehran. A comparative analysis of evapotranspiration maps between areas influenced by flood spreading and those unaffected revealed that flood spreading significantly reduces evapotranspiration rates. On an average, flood spreading resulted in a 15% reduction in actual evapotranspiration. This decrease is mainly attributed to enhanced soil moisture content, improved physiological conditions of vegetation, and reduced water stress experienced by plants in flood-affected areas. Additionally, the results indicated that flood spreading is vital in facilitating groundwater recharge, increasing the soil’s water retention capacity, and promoting healthier and more sustainable plant growth. Over time, these impacts contribute significantly to the long-term sustainability of water resources and the ecological stability of the region. The SEBS model outputs were systematically compared with field measurements to assess the accuracy of the model's predictions. Statistical indices such as the coefficient of determination (R²) and the mean absolute error (MAE) were employed for validation. The statistical evaluation showed that the R² value was 0.68 and the MAE was 0.48 mm per day, indicating a satisfactory level of accuracy and validating the effectiveness of the SEBS model under the climatic conditions of the Chahdabab Plain. Conclusion This study demonstrates that the SEBS model can serve as an effective tool for estimating actual evapotranspiration in arid and semi-arid regions. The findings reveal that precise calibration using local data significantly enhances the model’s predictive performance. These results emphasize the importance of integrating accurate climatic, topographic, and vegetation information to improve the reliability of evapotranspiration models. Furthermore, the evaluation of flood spreading impacts indicates that this technique can be adopted as an efficient strategy for water resource management. By increasing soil moisture, reducing surface temperatures, and enhancing the physiological condition of plants, flood spreading contributes to lower agricultural water consumption and improved crop yields. Additionally, this process supports groundwater recharge and facilitates the restoration of water-dependent ecosystems. The observed reduction in evapotranspiration following flood spreading interventions highlights the effectiveness of this approach in conserving water resources and promoting sustainable agricultural development. The outcomes of this research offer valuable insights for designing comprehensive water management programs in arid and semi-arid regions. Moreover, they provide practical strategies for strengthening the resilience of vulnerable ecosystems to the adverse impacts of climate change. Overall, the findings underscore the critical role of flood spreading and precise modeling techniques in advancing sustainable water and agricultural practices in water-scarce environments.   مدیریت منابع آب, سنجش از دور, تبخیر و تعرق, بیلان آبی. Water Resources Management, Remote Sensing, Evapotranspiration (ET), Hydrological Balance 64 77 http://jwmsei.ir/browse.php?a_code=A-10-207-6&slc_lang=fa&sid=1 Rahman Sharifi رحمان شریفی r.sharifi1346@gmail.com 100319475328460018967 100319475328460018967 No Soil Conservation and Watershed Management Department, Tehran Agricultural and Natural Resources Research Center مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان تهران fatemeh Barzegari Banadkooki فاطمه برزگری بنادکوکی fa_barzegar@yahoo.com 100319475328460018968 100319475328460018968 Yes Engineering Department, Payame Noor University دانشکده فنی و مهندسی دانشگاه پیام نور Ghoban Rostami zad قباد رستمی زاد rostamizad660@gmail.com 100319475328460018969 100319475328460018969 No Soil Conservation and Watershed Management Department, Zanjan Agricultural and Natural Resources Research Center مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان زنجان