بهینه ‌سازی و امکان‌ سنجی استفاده از سامانه‌های استحصال آب باران در اردبیل

ایران از لحاظ اقلیمی جزء مناطق خشک و نیمه‌خشک جهان محسوب می‌شود که از میزان بارندگی نسبتاً پایینی برخوردار است. از طرفی، توزیع این میزان بارندگی در کشور نیز مناسب نبوده و اغلب در سواحل دریای خزر و نیمه غربی تا جنوب غرب کشور رخ می‌دهد. این عوامل، لزوم انجام اقدامات مدیریتی در جهت غلبه بر بحران آب را به دنبال دارد. یکی از راهکارهای عملی در راستای مدیریت منابع آب، اجرای سامانه‌های استحصال آب باران می‌باشد که باید به صورت بهینه طراحی شوند تا سامانه توجیه اقتصادی داشته باشد. در این مقاله با هدف ارزیابی و بهینه‌سازی سامانه‌های استحصال آب باران، داده‌های 42 ساله بارش روزانه شهرستان اردبیل تحت سناریو یک خانه مسکونی با سطح آبگیر 100 و 200 متر مربع و دارای چهار سکنه در نظر گرفته شد. شبیه‌سازی سامانه در نرم‌افزار متلب انجام و قابلیت اطمینان مخازن و نسبت سرریز برای حجم‌های مختلف مخازن محاسبه شد. در نهایت، بهینه‌سازی حجم مخازن با استفاده از الگوریتم ژنتیک انجام شد. نتایج نشان داد که برای پشت‌بام 100 متر مربع، استفاده از مخزن 5/0 متر مکعبی بیشترین سودآوری را داشته و با نصب این مخزن، سالانه 17 درصد در مصرف آب صرفه‌جویی خواهد شد. همچنین مخزن بهینه برای پشت‌بام 200 متر مربع برابر با 5/1 متر مکعب انتخاب شد که با استفاده از آن می‌توان در هر سال حدود 32 درصد در مصرف آب صرفه‌جویی کرد. ارقام بدست آمده برای درصد صرفه جویی در مصرف آب حاکی از پتانسیل بالای شهرستان اردبیل برای اجرای سامانه‌های استحصال آب باران است.

optimization and feasibility of using rainwater harvesting systems in ardabil

introduction arid and semi-arid climates prevail in iran. the precipitation is also sparsely distributed in most areas of the country. therefore, there is a need for management measures to overcome the water crisis. one of these measures is designing rainwater harvesting systems that can meet some of the non-potable needs and reduce runoff in urban areas. the main components of rainwater harvesting systems in residential regions include the catchment area, storage tank, and water transfer system from the catchment area to the tank. the storage tank is the biggest investment in a rainwater harvesting system, as most buildings are not equipped with a storage system. therefore, tank capacity should be determined optimally to minimize project implementation costs. the stored water volume and the project profit increases with increasing the tank volume. however, in this case, the price of the tank increases. therefore, the tank capacity should be optimally designed to justify economic exploitation.materials and methods in order to evaluate the feasibility of using rainwater harvesting systems, the tanks’ volume was optimized. due to the higher rainfall of ardabil relative to the average rainfall of the country, it is expected that this area has a good potential for the implementation of rainwater harvesting systems. therefore, this region was selected as the study area under the scenario of a residential house with ​​100 and 200 m2 catchment areas and four inhabitants. the amount of rainfall in the region is one of the primary parameters in determining the volume of rainwater collection tanks. some of the precipitated water is always inaccessible due to evaporation from the surface. nonetheless, since there is almost no sunlight during and immediately after rainfall, and also the received water enters the reservoirs shortly after precipitation, evaporation was assumed to be zero. daily precipitation data for 42 years (from 1977 to 2019) were retrieved from the ardabil meteorological site. the daily water balance modeling method was used to analyze the rainwater harvesting systems due to the simplicity of interpretation, high accuracy and better general acceptance. daily precipitation data were entered into this model and used as the primary source to meet the domestic demands. simulation of rainwater harvesting systems was performed using daily precipitation data in matlab software, and the reliability of these systems was calculated for different tank volumes. then, considering the price of drinking water and the current price of tanks in the market, the optimal volume of tanks was calculated using the genetic algorithm. finally, the annual volume of water supply and the amount of water savings in case of using the optimal volumes of tanks were also estimated.results and discussion the results showed that the percentage of reliability is directly related to the volume of the tank, thus, the reliability percentage also increases with increasing the tank capacity. as the volume of the tank increases, the slope of the increasing reliability percentage decreases continuously, to the point that this slope becomes almost zero. comparing the reliability percentage obtained for 100 and 200 m2 rooftops indicated that 200 m2 rooftop had a higher reliability percentage than 100 m2 rooftop due to receiving much more rainfall and meeting the water need for a longer duration. by comparing the results of overflow ratio for 100 and 200 m2 rooftops, it can also be concluded that using a fixed size tank, the overflow in 200 m2 rooftop is higher, which is due to receiving more water volume than 100 m2 rooftop. the results also showed that by using a 5 m3 tank, 44.5 and 24 m3 of water can be stored annually from the 200 and 100 m2 catchment areas, respectively, these are equal to 28 and 19 m3, respectively, if 1 m3 tank is used. the optimal tank volumes for 100 and 200 m3 rooftops are equal to 0.59 and 1.66 m3, respectively. since the tanks are made in specific volumes, the obtained volumes were rounded to the closest volumes available in the market. thus, a 1.5 m3 tank was used for a 200 m2 rooftop and a 0.5 m3 tank was applied for a 100 m2 rooftop.conclusionapplication of a tank of 0.5 m3 for the rooftop of 100 m2 was the most profitable for saving 17% of water consumption, annually. moreover, the optimal tank volume for the 200 m2 rooftop was selected to be 1.5 m3, saving about 32 % of water consumption per year. water-saving percentages indicate the high potential of our study area for the implementation of rainwater harvesting systems.