بررسی پتانسیل ذخیره آب باران و قابلیت اطمینان مخازن سامانه استحصال آب باران: مقایسه‌ای بین شمال، مرکز و غرب شهر تهران

نویسندگان

چکیده

با توجه به وضعیت اقلیمی و مصارف بیش از حد آب در اکثر شهرهای بزرگ می‌توان مشکل کم‌آبی را تا حد مطلوبی با استفاده از سامانه‌های جمع‌آوری آب باران کاهش داد. «قابلیت اطمینان» به درصدی از کل روزهای سال گفته می‌شود که بتوان توسط آب جمع‌آوری‌شده در مخازن، تقاضای موردنظر ساکنان را تأمین کرد. «پتانسیل ذخیره‌ی آب باران» به حجمی از رواناب گفته می‌شود که قبل از تبدیل به سیلاب توسط مجموعه‌ای از اقدامات در مخزن ذخیره شود و مورد استفاده قرار ‌گیرد. هدف از این تحقیق، برآورد قابلیت اطمینان مخازن ذخیره‌سازی آب باران و بررسی پتانسیل ذخیره‌سازی آب باران بود. در این مطالعه، از برقراری بیلان آبی بین ورودی (بارندگی) و خروجی (سرانه مصرف خانگی) برای تجزیه و تحلیل عملکرد و طراحی بهینه‌ حجم مخازن در سه منطقه متفاوت از تهران شامل مرکز، غرب و شمال استفاده شد. تفاوت در برخی از مشخصات این مناطق از قبیل میزان بارندگی و توپوگرافی قابل توجه است. تعدادی از نمودارهای قابلیت اطمینان مخازن آب باران برای مصارف داخلی در رابطه با حجم مخزن، مساحت پشت‌بام، تعداد افراد در یک خانه (تقاضای آب) و درصدی از کل نیاز آبی که توسط آب باران ذخیره‌شده تأمین می‌شود، ارائه شد. نتایج نشان داد که برای پشت‌بام‌ با مساحت ??? مترمربع، قابلیت اطمینان ??? درصد حتی با یک مخزن بسیار بزرگ (????? لیتر) قابل دستیابی نیست، و اینکه قابلیت اطمینان مستقل از اندازه‌ی مخزن برای مخازن با اندازه‌های بزرگ‌تر از ????-???? لیتر بوده و وابسته به موقعیت مکانی منطقه است. همچنین، متوسط ذخیره‌ی آب باران در مخازن به‌صورت سالانه برای هر سه مکان تعیین شد. نتایج نشان داد که بیشترین میزان ذخیره آب باران در مخزن برای پشت‌بام با مساحت ??? مترمربع در شمال تهران و برابر با ??? مترمکعب بود، و کمترین ذخیره آب باران در مخزن برای پشت‌بامی با مساحت ??? مترمربع (برابر با ?? مترمکعب) در غرب تهران بود. به‌طور کل، از نتایج مشخص شد که سامانه‌ی استحصال باران در منطقه‌ی شمال تهران از قابلیت اطمینان و همچنین امکان ذخیره‌ی آب باران بیشتری نسبت به مرکز و غرب تهران برخوردار است. ایستگاه‌های باران موردنظر (که در فاصله ?? تا ?? کیلومتری از هم واقع شده‌اند) به‌علت تفاوت در شرایط تغییرات بارندگی و بعضاً توپوگرافی، نتایج آنها به‌طور محسوسی متفاوت بود. این نتایج نشان می‌دهد که قابلیت اطمینان مخازن آب باران می‌تواند به‌طور قابل توجهی در یک شهر بزرگ مانند تهران متفاوت باشد که سبب تغییر در الگوی طراحی سامانه آب باران خواهد شد.

کلیدواژه‌ها


عنوان مقاله [English]

Reliability and Storage analysis of rainwater Reservoirs: Comparison between North, Center, and West of Tehran

نویسندگان [English]

  • Oweis Mollaei
  • Mehdi Kouchakzadeh
  • Fereshteh Haghighi feshi
چکیده [English]

With increasing population and changing climate regime, water supply systems in many cities of the world are under stress. To tackle this problem, water authorities are adopting several measures including demand management and identifying alternative water sources such as stormwater harvesting, greywater and wastewater reuse and desalination. Among all the alternative water sources, stormwater harvesting perhaps has received the highest level of attention. Regarding to excessive water consumption in large cities, the problem of water shortage can be reduced to the extent desirable by using rainwater harvesting systems. “Reliability” is percentage of total days in a year when the water collected in the reservoirs is able to supply the demand of residents. “Rainwater storage potential” is the volume of runoff that is collected and used by a series of actions in the tank, before becoming a flood.
The aim of this study was to estimate the reliability of rainwater storage tanks and to investigate the potential of rainwater storage. In the current study, the daily water balance between the rainfalls as input and domestic water-consumption per capita as output were used for the performance analysis and design the optimum of rainwater tanks, at three different regions of Tehran (center, north and west). These three different regions of Tehran are distinct due to notable different rainfall and topography characteristics. Charts of reliability of rainwater storage were produced for domestic rainwater tanks due to tank volume, roof area, number of people in a house (i.e. water demand) and percentage of total water demand to be satisfied by the harvested rainwater.
In this study, the reliability of rainwater harvesting system was investigated for rainwater saving and non-potable water supply in three different regions of Tehran. It was found that for a relatively small roof area (??? m?), ???% reliability could not be achieved even with applying a very large tank (??,??? L). This roof area was very small to collect the appropriate amount of rainfall. In this case, the accumulated rain was used quickly and the reservoir remained empty until the next rain event occurred. For the larger reservoirs, the reliability remained constant; in which case, part of the volume of the reservoir or the entire volume remained in most of the time because the roof area for collecting rainwater was enough, or the demand for water was not high. For a large roof area (??? m?), about ??% reliability can be achieved with a tank size of ??,??? L. Reliability was independent of tank size for the sizes larger than ????–???? L; in these rang of size, the reliability depends on the region (location). Also, the average rainwater storage in reservoirs was determined annually for each of the three locations. The results showed that the amount of rainwater storage increases with increasing roof area. It was found that with increasing the daily water demand of building residents, the days of water supply by rainwater saving from roofs would decrease. According to the results, it can be stated that the effect of increasing the volume of the reservoir in storing rainwater for the roofs with larger areas were greater than the roofs with small areas because, the roofs with the small area do not fill the reservoir. The runoff overflow from the reservoir was often carried out on the large roofs, which can be reduced by increasing the volume of the reservoir (reducing the runoff from the reservoir and adding to the amount of rainwater stored). The maximum rainwater storage for a roof area of ??? m? were ??? m?, annually in north of Tehran. The minimum storage for a roof area of ??? m? were ?? m?, annually in west of Tehran. In general, the results showed that north of Tehran has more reliability and also more rainwater storage than the center and west of Tehran. The considered rainfall stations (which are located ?? to ?? km apart) produced significantly different results due to the difference in rainfall conditions and topographic variability. The results revealed that rainwater tank reliability can vary significantly within a large city like Tehran, which emphasizes the need to change the design pattern of considering a single annual rainfall value for the purpose of rainwater tank sizing.

کلیدواژه‌ها [English]

  • Climatic conditions
  • Daily water balance
  • Reliability
  • Rainwater storage tanks