Abstract
Nowadays, rainwater harvesting systems, especially in urban regions, are considered as one of the approaches in water resources management. It is globally being studied as an effective plan, as well. Therefore, considering the requirement of attention to the components of rainwater harvesting system and reservoir volume optimization, this study has been launched toward the optimization of required reservoir supply volume for enabling the maximum supply with the least expenses. In this work, the rainfall statistics of Birjand synoptic station was utilized as the base information for hydrologic analysis. To estimate water-consumption-rate, some questionnaires were distributed among residents. To determine an optimal volume for cisterns, simulated water harvesting systems were analyzed through mass curve analysis in two conditions, i.e. normal and wet years. Five scenarios were defined, in terms of water use rate in dry wet season. In the first scenario (the basic scenario without any reduction in water utilization rate in wet season), reservoir volume of the buildings 1-7 in normal year were estimated as 9794, 6099, 11021, 6282, 6196, 7026, and 17146 liters, respectively. However, in wet conditions (years), reservoir volume of the buildings 1-7 were estimated as 10104, 6931, 23013, 11774, 6488, 12501, and 36972 liters, respectively. For the scenarios 2-5, with 10, 20, 30, and 50%, respectively, decrease in residents’ water consumption rate in wet season, water was more supplied for dry season. However these scenarios resulted in some decrease or increase in reservoir volume. Obtained optimal reservoir volume of each scenario was compared with the basic scenario. Results have shown that the mass curve approach is appropriate for determining the volume of reservoir except for the buildings where the consumption curve was higher than input curve. In these cases, trial and error approach was identified more appropriate in reservoir volume estimation.