Feasibility of rainwater harvesting from residential rooftops in Jordan

Rainwater harvesting is adopted to face water scarcity in arid regions. Many studies were developed in Jordan to estimate the potential of water harvesting for several uses. However, the precise estimation of water saving and cost benefits for the potential of rainwater harvesting from the roofs of residential urban areas is insufficient. Therefore, the objective of this study was to investigate the feasibility of rainwater harvesting from residential rooftops in all the eighty-nine Jordanian districts. The forecast number of buildings was calculated from 2016 to 2025 using building growth rate, where the number of houses and villas was adopted only. The long-term rainfall average from 1937 to 2017 was used. Two scenarios were used to assess the potential of rainwater harvesting; numerical (as scenario 1) and tabulated by plumbing code (as scenario 2) for the years from 2019 to 2025. Also, the growth rate of one cubic meter of water cost was calculated to find the money saving potential for the water companies in Jordan. The results indicated that the water harvesting potential was different between two scenarios in the districts which have annual rainfall more than 100 mm was efficient in scenario 1 compared to scenario 2 with the projected financial return which was increased from $5.4 million at 2019 to reach $33.4 million at 2025, while in the districts which have annual rainfall less than 100 mm was more efficient in scenario 2 compared to scenario 1 with the projected financial return which was increased from $2.4 million at 2019 to reach $14.6 million at 2025.