شبیه سازی هیدرولوژیکی بارش-رواناب مبتنی بر اطلاعات ماهواره ای تحت تاثیر سناریوهای اقلیمی در حوزه‌ آبخیز تکاب

برآورد خروجی حوزه‌ آبخیز یک گام مهم در برنامه ریزی و مدیریت منابع آب سطحی است، به ویژه در حوزه‌های آبخیزی که فاقد داده های قابل اطمینان از متغیرهای اقلیمی هستند. در راستای ضرورت این مساله در مطالعه‌ حاضر به سبب توزیع نامناسب مکانی ایستگاه های هواشناسی در حوزه‌ آبخیز تکاب، از تصاویر و اطلاعات ماهواره ای جهت ارزیابی اثرات احتمالی عوامل اقلیمی شامل بارش و دما بر رواناب استفاده شد. بدین‌منظور برای بررسی تغییرات ماهانه‌ بارش و دما از سال 1998 تا 2020 به‌ترتیب از اطلاعات ماهواره ای trmm و fldas استفاده شد. نتایج ارزیابی، دقت مناسب این اطلاعات ماهواره ای را در مقایسه با مقادیر مشاهداتی برای بارش و دما به‌ترتیب با همبستگی 0.78 و 0.98 نشان می دهد. بررسی داده های بارش حوزه‌ آبخیز نشان داد که بیشترین میزان بارندگی در 3 ماه میلادی آوریل، مارچ و نوامبر معادل ماه های فروردین، اسفند و آبان رخ می دهد که به‌ترتیب 53.14، 40.45 و 39.61 میلی متر و تقریبا معادل 45 درصد از کل بارندگی سالانه است. همچنین بیشترین و کمترین دمای متوسط محدوده به‌ترتیب در ماه های میلادی ژوئیه و ژانویه معادل ماه های تیر و دی بوده که به‌ترتیب 24.20 و 3.49- درجه سانتی گراد برآورد شده است. همچنین روند تغییرات بارش و دما با آزمون های ناپارامتری من-کندال و شیب سن مورد بررسی قرار گرفت. نتایج ارزیابی به طور کلی نشان از روند افزایشی غیرمعنادار بارش و دما در کل منطقه مطالعاتی داشت. در ادامه از مدل مفهومی ihacres با استفاده از داده های دما و بارش اطلاعات ماهواره ای برای شبیه سازی رواناب حوزه‌ آبخیز مورد استفاده قرار گرفت. به منظور پیش بینی رواناب تولیدی تحت تاثیر تغییر اقلیم و ارزیابی سناریوهای مختلف اقلیمی در آینده نیز از مدل ihacres استفاده شد. بدین منظور از گزارشات برنامه پنجم توسعه تحت عنوان سناریوهای انتشار rcp (rcp2.6 و rcp8.5) برای سال های آتی تا سال 2100 استفاده شد. نتایج شبیه سازی جریان تحت سناریو rcp2.6 حاکی از آن است که بیشترین افزایش دبی در دوره‌ آتی برای حوزه‌ آبخیز تکاب مربوط به ماه های دسامبر، نوامبر و ژانویه برآورد شد. همچنین تحت سناریو rcp8.5 بیشترین افزایش دبی در دوره‌ آتی به‌ترتیب در ماه‌های اوت، ژوئیه و ژانویه محاسبه شده است. از طرفی مطابق شبیه سازی بیشترین کاهش دبی تحت هردو سناریو به‌ترتیب در ماه های آوریل و می به دست آمد. طبق نتایج، متوسط دبی سالانه طبق سناریوهای اقلیمی rcp2.6 و rcp8.5 به‌ترتیب معادل 8.33 و 5.09 مترمکعب برثانیه پیش بینی شد.

the rainfall-runoff hydrological simulation model based on satellite products with the effect of climate scenarios in the takab watershed

runoff is an important hydrological component in the assessment of water resources. most water resource applications rely on runoff as an essential hydrologic variable. the hydrology of watersheds is influenced by many factors, including climate change. watershed discharge estimation is an important step in surface water resources planning and management, especially in watersheds that lack data. in this study, due to the uneven spatial distribution of meteorological stations in the study area of takab, satellite images and products were used to evaluate the possible effects of climatic factors, including rainfall and temperature on runoff. therefore, in the first step to analyze rainfall and temperature changes from 1998 to 2020, trmm and fldas satellite products, respectively, were evaluated using different statistical criteria with takab synoptic station data to ensure their accuracy and suitability as inputs for hydrological models such as the ihacres model. in the second step, considering that the selection of the rainfall-runoff model requires knowing the capabilities and limitations of the hydrological models of the watershed, which depends on access to various watershed parameters. however, , a model should be used that provides reliable results despite limited inputs.materials and methodsthe takab watershed is one of the 25 sub-watersheds of lake urmia, located south of this watershed. the only permanent and significant river in this watershed is the sarogh chay river, which is the longest river in the area. in this study, the non-parametric mann-kendall and sen’s slope tests were used to analyze the trend of rainfall and temperature changes. subsequently, the ihacres model was used to simulate the river discharge using temperature and rainfall data from satellite products. additionally, in this study, the ihacres model was used to predict runoff generation under the influence of climate change and evaluate different climate scenarios. this model is an integrated conceptual model for rainfall-runoff simulation. the ihacres model has always been of interest due to its low data requirements and high accuracy in runoff estimation. for this purpose, this study used the intergovernmental panel on climate change (ipcc) representative concentration pathways (rcps) scenarios (rcp4.5 and rcp8.5) for projections up to 2100. to evaluate the ihacres model, the determination coefficient (r2), nash-sutcliffe efficiency coefficient (nse), root mean square error (rmse), and bias error (bias) were used during the calibration and validation periods.results and discussion in the first step, the analysis of the rainfall data of the takab watershed showed that the highest amount of rainfall occurs in april, march, and november, respectively, which together accounts for approximately 45% of the total annual rainfall of the study area, with estimated values of 53.1, 40.4, and 39.6 mm per month, respectively. also, the highest and lowest average temperatures in the region occur in july and january, respectively, with estimatedvalues of 24.2 ℃ and -3.4 ℃, respectively. in the second step, the simulated discharge results from the rcp2.6 scenario indicated that the greatest increase in discharge in the future for the takab study area was estimated for december, november, and january. similarly, under the rcp8.5 scenario, the highest increases in future discharge were projected for august, july, and january, respectively. according to the results, according to the rcp2.6 and rcp8.5 climate scenarios, the predicted average annual discharge was 8.3 and 1.5 cubic meters per second, respectively. the model evaluation parameters for the ihacres model during the 14-year calibration period were calculated as follows: r2 = 0.82 and 0.80, rmse = 1.4 m3 s-1, and bias = 0.42. similarly, during the validation period, these values were calculated as r2 = 0.71 and 0.68, rmse = 4.7 m3 s-1, and bias = 0.1, respectively.conclusionthe results of the present study showed that the watershed has been affected by increasing temperature and precipitation trends during the statistical period. the results of the trend analysis and satellite data evaluation were compared with and confirmed by previous research. the ihacres model simulation results demonstrated that this model has a strong ability to simulate watershed discharge and is consistent with the results of other studies. however, while the model performs well for the low-flow conditions, it struggles with accurately simulating peak discharges, as noted in several studies. according to the rcp2.6 scenario, the predicted discharge for the future period is expected to increase compared to the baseline period. the annual discharge changes rate under this scenario was calculated as +19.4%, which can be attributed to an increase in average rainfall, a reduction in greenhouse gases, and relatively stable temperatures in the future. however, according to the rcp8.5 scenario, a decline in river discharge was projected compared to the baseline period. the annual simulated discharge change under this scenario was estimated as -1.68%, resulting from increased greenhouse gas emissions, higher temperatures, and notable decrease in rainfall. one of the major consequences of this scenario would be a shortage in the timely supply of agricultural water and a significant reduction in food security.