چکیده:
با توجه به اهمیت و نقش میزان جریان در مطالعات منابع آب، در این پژوهش روشهای تجربی برآورد جریان رودخانه در مناطق بدون ایستگاه آبسنجی بررسی شدهاند. عملکرد این روشها در تخمین جریان سطحی خروجی از محدودههای مطالعاتی حوضة سفیدرود بزرگ که ایستگاه آبسنجی دارند، بررسی شده است. جریان سطحی تخمینی براساس روشهای تجربی مختلف با جریان سطحی مشاهداتی ثبتشده در ایستگاههای آبسنجی مقایسه و نتایج از منظر شاخصهای آماری همچون خطا ارزیابی شده است. انتخاب این حوضه با توجه به گستردگی جغرافیایی، تنوع اقلیمی و ویژگیهای فیزیوگرافیک متنوع آن صورت گرفته است. روشهای جاستین، کوتاین، سازمان تحقیقات کشاورزی هندوستان، دپارتمان آبیاری هندوستان، تورک، لازی، خوسلا، انگلی- دیسوزا و SCS-CN مربوط به سازمان حفاظت خاک آمریکا در این پژوهش بررسی شدهاند. نتایج در محدودههای مختلف حوضة سفیدرود حاکی از عملکرد بهتر روشهای دپارتمان آبیاری هندوستان، جاستین و کوتاین بوده است. در پایان با توجه به نتایج بهدستآمده، روش جاستین برای محدودههایی با گرادیان ارتفاعی و دمایی شدید و در عین حال ضریب جریان زیاد توصیه میشود. روش سازمان آبیاری هندوستان نیز برای محدودههای دارای نسبت زیاد رواناب به بارش عملکرد قابل قبولی داشته است؛ اما هرچه نسبت رواناب به بارش کمتر از 2/0 باشد، عملکرد این روش ضعیفتر میشود. روش کوتاین در بیشتر محدودهها عملکردی متوسط دارد که بر این اساس این روش بهمثابة انتخابی محافظهکارانه توصیه میشود.
Extended Abstract: 1- Introduction: Estimation of discharge in ungauged basins is of prominent importance in hydrologic and water resource management studies; however, it is not possible to determine the runoff coefficient in different watersheds without streamflow data. In many study areas of the country (unit of hydrological basis and balance of water resources in the studies of the Ministry of Energy), there is no hydrometric station to measure the surface flow out of the area. Several methods have been introduced to estimate the discharge of ungauged basins, which can be classified into three main categories. The first category contains the methods that make a relation between precipitation and the produced runoff (such as the Inglis and De’Souza and the Indian Department of Irrigation (IDOI) methods). The second category includes the methods that estimate annual runoff deficit and predict the yearly runoff accordingly (such as Turc, Langbein, Coutagine, and Khosla methods). The third category covers the methods that take into account the physiographic characteristics of basins to estimate runoff (such as the Indian Council of Agricultural Research (ICAR), Justin, and Lacey methods). The SCS Curve Number (CN) method is also among the most common methods of estimating runoff produced by rainfall and considers various conditions in its formulations; nonetheless, determining the CN and its initial absorption coefficient is still challenging. The aim of the present study is to evaluate the efficiency of different empirical methods in the estimation of runoff in watersheds with different hydrologic and physiographic characteristics and climatic conditions in addition to giving some insights on the selection of the proper runoff estimation methods in ungauged basins. 2- Methodology: In this study, the application of empirical methods in the calculation of the outgoing discharge from various areas in the Sefidroud watershed was investigated. The Sefidroud watershed has a total number of 11 areas, 10 of which have hydrometric stations in their outlets. For these ten sub-basins, the observed annual runoff was compared with the results yielded by the aforementioned empirical methods, and the efficiency of each method was assessed accordingly for each sub-basin. The Root Mean Squared Error (RMSE), Standard Deviation (SD), Correlation Coefficient, and the Centered Root Mean Squared Deviation (CRMSD) were used to analyze the data. The runoff estimation methods investigated in this study included Khosla, Lacey, Inglis De’Souza, Coutagine, Turc, ICAR, IDOI, Justin, and the SCS-CN methods. Moreover, the authors of the present study tried to find the optimized value of the initial absorption coefficient in the SCS-CN method in order to obtain a reasonably accurate estimation of runoff for each sub-basin. 3- Discussion: The results of the present study indicated that the Khosla and the SCS-CN methods with an initial absorption coefficient of 0.05 and 0.2 showed the poorest performance in all sub-basins. Moreover, the Inglis De’Souza method was not applicable in Iran’s sub-basins due to its different approach in dealing with plains and highlands. Because the study areas in the catchments of Iran are all a combination of plains and elevations and sometimes include a combination of several plains and several elevations with different characteristics. The optimized values of the initial absorption coefficients varied between 0.0006 and 0.25, which implies that a specific value of initial absorption cannot be used in all of the sub-basins to achieve the best accuracy in the estimation of runoff. Comparison between the results yielded by other methods (i.e. Turc, Coutagine, IDOI, ICAR, and Justin) with the observed streamflows indicated that the choice of the best method depends on the error index used for comparison. In other words, the Justin method had the best performance in terms of correlation with the observed runoff in the Sefidroud watershed. But, in terms of the RMSE error index, the IDOI method generally performs better. Finally, the Coutagine method had a good performance in terms of both correlation and RMSE in the main study areas. 4- Conclusion: According to the results of the present study, the Justin method is recommended for areas that have a high altitude and temperature gradient and at the same time have a high flow coefficient. The IDOI method performs best for sub-basins that have a high runoff to rainfall ratio. As this ratio decreases below 0.2, the IDOI method is likely to produce poorer results. The Coutagine method showed a moderate performance in most of the studied areas, which suggests that it can be employed to produce conservative results in many areas under study. Keywords: Empirical Methods, Runoff Estimation, Ungauged Basins, the Sefidroud Watershed. References: - Dalavi, P., Bhakar, S. R., Bhange, H. N., & Gavit, B. K. (2018). Assessment of Empirical Methods for Runoff Estimation in Chaskaman Catchment of Western Maharashtra, India. International Journal of Current Microbiology and Applied Sciences, 7(5), 1511-1515. - Golshan, M., & Ebrahimi, P. (2014). Estimation of the Runoff by Empirical Equations in Dry and Mid-Dry Mountainous Area without Stations (Case Study: Madan Watershed, Qazvin Province-Iran). Bulletin of Environment, Pharmacology, and Life Sciences, 3(3), 97-106. - Gupta, B. L., & Gupta, A. (1992). Engineering hydrology. New Delhi: Standard Publishers. - Hawkins, R. H., Ward, T. J., Woodward, D. E., & Van Mullem, J. A. (2009). Curve Number Hydrology: State of the Practice. American Society of Civil Engineers. - Hong, Y., Adler, R. F., Hossain, F., Curtis, S., & Huffman, G. J. (2007). A First Approach to Global Runoff Simulation Using Satellite Rainfall Estimation. Journal of Water Resources Research, 43(8), 1-8. - Horvat, B., & Rubinic, J. (2006). Annual Runoff Estimation - An Example of Karstic Aquifers in the Transboundary Region of Croatia and Slovenia. Hydrological Sciences Journal, 51(2), 314-324. - Inglis, C. C., & De’Souza, A. J. (1930). A Critical Study of Runoff and Floods of Catchments of Bombay Presidency with a Short Note on Losses from Lake by Evaporation. Technical Paper, 30. - Jaafar, H. H., Ahmad, F. A., & El Beyrouthy, N. (2019). GCN250, New Global Gridded Curve Numbers for Hydrologic Modeling and Design. Journal of Scientific Data, 6(1), 1-9. - Khopade, D. K., & Oak, R. A. (2014). Estimation of Runoff Yield for Nira Deoghar Catchment Using Different Empirical Equations. The International Journal of Engineering and Science, 3(6), 75-81. - Khosla, A. N. (1949). Appraisal of Water Resources Analysis and Utilization of Data. Proceedings of United Nations Scientific Conference on Conservation and Utilization of Resources. - Khosravi, K., Mirzai, H., & Saleh, I. (2013). Assessment of Empirical Methods of Runoff Estimation by Statistical Test (Case Study: BandakSadat Watershed, Yazd Province). International Journal of Advanced Biological and Biomedical Research, 1(3), 285-301. - Langbein, W. B. (1949). Annual Runoff in the United States. Washington DC, USA: US Geol. Survey Circular 52. - Lewis, D., Singer, M. J., & Tate, K. W. (2000). Applicability of SCS Curve Number Method for a California Oak Woodlands Watershed. Journal of Soil and Water Conservation, 55(2), 226-230. - Meresa, H. (2019). Modelling of River Flow in Ungauged Catchment Using Remote Sensing Data: Application of the Empirical (SCS-CN), Artificial Neural Network (ANN) and Hydrological Model (HEC-HMS). Journal of Modeling Earth Systems and Environment, 5(1), 257-273. - Plummer, A., & Woodward, D. E. (1998). Origin and Derivation of Ia/S in the Runoff Curve Number System. International Water Resources Engineering Conference, ASCE, Reston, USA, 1260–1265. - Raghunath, H. M. (2006). Hydrology, Principles, Analysis, and Design. New Delhi: New Age International Publishers. - Rawat, K. S., Singh, S. K., & Szilard, S. (2020). Comparative Evaluation of Models to Estimate Direct Runoff Volume from an Agricultural Watershed. Journal of Geology, Ecology, and Landscapes, 1-15. - SCS (1985). National Engineering Handbook, Section 4: Hydrology. US Soil Conservation Service, USDA, Washington, DC. - Shi, Z. H., Chen, L. D., Fang, N. F., Qin, D. F. & Cai, C. F. (2009). Research on the SCS-CN Initial Absorption Ratio Using Rainfall-Runoff Event Analysis in the Three Gorges Area, China. Catena Journal, 77(1), 1-7. - Sobhani, G. (1976). A Review of Selected Small Watershed Design Methods for Possible Adoption to Iranian Conditions. (n.p). - Turc, L. (1955). Le bilan d’eau des sols: relations entre les precipitations, l’evaporation et l’ecoulement. Journees de l'hydraulique, 3(1), 36-44. - Varshney, R. S. (1979). Engineering Hydrology. New Chand and Bros.
خلاصه ماشینی:
روش تجربي دپارتمان آبياري هندوستان که گوپتا و گوپتا٣ (١٩٩٢) تشريح کرده اند، ازجمله روش هـايي اسـت کـه عملکرد آن در مطالعات پيشين به ويژه در حوضه هاي آبريز ايران مطلوب بوده است ؛ براي نمونه تيموريان و همکـاران (١٣٩٣) در برآورد رواناب حوضۀ بوشگيان ، اين روش را برترين روش تشخيص داده اند.
Calibrated λ parameters of CN method in the hydrology study areas of the Sefidroud watershed (به تصویر صفحه رجوع شود)مقدار شاخص خطاي RMSE روش هاي مختلف در تخمين جريان خروجي از محدوده هاي مطالعاتي مختلـف در جدول ٦ ارائه شده است .
RMSE values between observed and computed streamflow of the empirical methods for the hydrology study areas (به تصویر صفحه رجوع شود) 16 در حوضۀ سفيدرود، رواناب تخمين زده شده براساس رابطۀ تجربي خوسلا نسبت به ديگر روش هـا بـيش بـرآورد چشمگيري دارد و به همين دليل در مقايسۀ نتايج روش ها، اين روش ناديده گرفته شـده اسـت .
Taylor diagrams of Coutagine, Turk, IDOI, ICAR, Justine and SCS-CN methods, the hydrology study areas of the Sefidroud watershed براساس نتايج نمودارهاي شکل ٢ در محدودة مطالعاتي منجيل ، روش سازمان آبيـاري هندوسـتان (IDOI) بهتـرين عملکرد را دارد و پس از آن به ترتيب روش هاي جاستين ، تورک، کوتاين و ICAR قـرار دارنـد (بـا توجـه بـه ميـزان نزديکي به نقطۀ مشاهداتي ).