Assessing reliability of rainwater harvesting systems for meeting water demands in different climatic zones of Iran

Abstract

Assessing the performance of rainwater harvesting systems, which is one of the effective ways to cope with the water shortage crisis, leads to better management of these systems. In this paper, the reliability of rainwater harvesting systems and the overflow ratio of storage tanks were investigated for different climatic conditions, different volumes of tanks, and different roof areas. The results indicated that in the cities of Rasht, Sari, Tabriz, and Yazd, using a 10-m3 tank, non-potable water needs of a four-person family can be supplied from a 100-m2 roof area for 67.3, 42.98, 12.07, and 1.35% of the days during a year. Further, if a 1-m3 tank is used in Rasht, 50.67% of the total harvested water will be overflowed, which would decrease to 19.21% if the 10-m3 tank is replaced. For Tabriz, the ratio of overflow from the 5-m3 tank was zero, but for the city of Sari, even with use of a 10-m3 tank, 0.73% overflow occurred. In addition, for Yazd city, using a 1-m3 tank, an overflow of 48.4% occurred, but when the volume of the tank was increased to 2 m3, there was no overflow. For the city of Tabriz, the ratio of overflow from the 5-m3 tank was zero, but for the city of Sari, even using a 10-m3 tank, 0.73% overflow occurred. For a constant volume of storage, as long as the average rainfall of the area was high, the ratio of overflow was also elevated. The ratio of overflow, from the highest to the lowest, was related to the temperate climate of the Caspian Sea and the pseudo-Mediterranean climate, moderate and humid climate, mountainous climate, and desert hot and dry climate, respectively.