ارزیابی آماری عملیات بارورسازی ابرهای فلات مرکزی ایران در سال آبی 93-94

با توجه به وضعیت اقلیمی خشک و نیمه‌‌خشک ایران و کاهش متوسط بارش‌ها به‌خصوص در سال‌های اخیر، استفاده از روش‌های نوینی همچون بارورسازی ابرها به‌منظور دست‌یابی به منابع آب بیشتر موردتوجه قرار گرفته و با این هدف، بارورسازی ابرها از سال 1377 در کشور عملیاتی شده است. هدف از این تحقیق، ارزیابی آماری پروژه‌های بارورسازی ابرها در سال آبی 93-94 (ماه‏های ژانویه، فوریه و مارس سال 2015 میلادی) در مناطقی از فلات مرکزی ایران شامل استان‏های یزد، کرمان، فارس، اصفهان و برخی از مناطق مجاور با بهره‌گیری از رگرسیون چندگانه گام‌به‌گام است. در این تحقیق از دو رویکرد آماری استفاده شد. در رویکرد اول، بارش در ایستگاه‏های واقع در منطقه تحت‌تاثیر عملیات بارورسازی، بر اساس بارش در ایستگاه‏های خارج از این منطقه با استفاده از این رگرسیون‌خطی برآورد شده و سپس با در نظر گرفتن بازه اطمینان 90 درصد، اثرگذاری عملیات بارورسازی در هر ایستگاه تعیین شده است. در رویکرد دوم، حجم بارش در استان‏های تحت‌تاثیر عملیات بارورسازی بر اساس بارش در ایستگاه‏های خارج از محدوده تحت‌تاثیر بارورسازی با استفاده از رگرسیون‌خطی چندگانه گام‌به‌گام برآورد شده و سپس با در نظر گرفتن بازه اطمینان 90 درصد، اثرگذاری عملیات بارورسازی بر روی حجم بارش هر استان بررسی شده است. نتایج هر دو روش حاکی از تاثیرگذاری معنی‌دار عملیات بارورسازی در این سال در این مناطق بوده است. به گونه‏ای که حجم بارش در ماه فوریه در تمام استان‏های واقع در منطقه هدف عملیات بارورسازی از 15 تا 80 درصد افزایش داشته است.

Statistical Evaluation of Cloud Seeding Operations in Central Plateau of Iran in the 2015 Water Year

Iran is located in an arid and semiarid region and has experienced a reduction of average rainfall in recent years. This has turned the attention to the use of new methods such as cloud seeding to achieve more water resources. In this regard, cloud seeding operations have been carried out in the country since 1998. The purpose of this study was to evaluate cloud seeding projects in the 2015 water year (January, February, and March 2015) in the central region of Iran, including the provinces of Yazd, Kerman, Fars, Isfahan, and some adjacent provinces. The evaluation was performed statistically using stepwise multiple regression. Two different approaches have been used for evaluation. In the first approach, precipitation at stations located in the target area of cloud seeding operations is estimated based on the precipitation at stations in the control area using stepwise multiple regression and then taking into account a 90% confidence interval for this estimate, the effectiveness or ineffectiveness of the cloud seeding operation at each station is determined. In the second approach, the volume of precipitation in each province in the target area is estimated based on the precipitation in stations outside in the control area using stepwise multiple regression and then by considering a 90% confidence interval for this estimate, the effectiveness of cloud seeding operations on the rainfall volume of each province has been investigated. The target area in different months was selected based on the HYSPLIT model results. Due to the inconsistent spatial distribution of rain gauges in the target areas, parts of the target areas lacking enough rain gauges were excluded from further analysis. To define the boundaries of the exclusion areas, Inverse Distance Weighted (IDW) method was used to find the influence of the radius around each rain gauge. The influence radius values were selected as 93940, 89569, and 149015 m for the months of January, February, and March, respectively. Finally, the minimum value of 89569 m was selected as the influence radius. The results of both methods indicate the impact of cloud seeding operations this year in these areas. In particular, the volume of precipitation in February in all provinces located in the target area of cloud seeding operations has increased from 15 to 80 percent. Surface runoff generated from the increased precipitation due to cloud seeding were estimated by the two methods of Soil Conservation Service (SCS) and Rational method. The estimated surface runoffs generated by SCS and rational methods were 1318.5 and 1329.5 million m3, respectively. The groundwater recharge in the three months of January, February, and March is estimated as 105.3, 425.6, and 156.3 million m3, respectively. It is important to note that runoff and groundwater recharge estimations by the method used in this study are subject to high uncertainties, and the estimations can only represent the order of magnitude of impacts of cloud seeding operations, and therefore, exact numbers should not be used for water resources planning and management purposes. Further investigation in areas with more rain gauges can assist in a more accurate assessment of could seeding operations.