Abstract—This study was aimed to make an assessment for the potential of rainwater harvesting system in Thailand. Both hydrological performance and economic feasibility were used to develop the RWH model for Bangkok, the capital city of Thailand. Net present value (NPV) was applied to analyze the cost effectiveness of rainwater harvesting system. To be summarized, the rainwater harvesting can potentially save tap water consumption in buildings which also gain financial profit depending on the designated system. In this case study, the installation of the RWH system with rainwater tank with the capacity of 30 m 3 was suggested due to the ability to save approximately $13,370 with the payback period of 34.8 years. In addition, this method can also the demand of tap water resource for 46,509 m 3 . For the buildings with higher tap water demand or higher tap water tariff, installing rainwater harvesting system would be strongly recommended for the implementation of rainwater harvesting system. In order to enhance the water resource management towards sustainability, rainwater harvesting system should be considered for the building design later on. Index Terms—Green infrastructure, rainwater harvesting, sustainable water resource management. I. INTRODUCTION Sustainable development is a broad concept that places emphasis on today's livelihoods which affected the well-being of humanity in the future. Due to the current economic, social and environmental situations, the concept of sustainable development has still received unprecedented attention. However, one of the concept that is gaining attention for moving towards the sustainability goals is “Green infrastructure”. The “Green infrastructure” has the implications for utilizing natural methods in urban development in order to achieve the environmental and sustainable development goals. The examples are green roof Manuscript received January 11, 2018; revised July 2, 2018. This research was funded by the Ratchadapisek Sompoch Endowment Fund (2016), Chulalongkorn University (CU-59-002-IC). Paron Monjaiang and Orathai Chavalparit are with the Department of Environmental Engineering, Chulalongkorn University, Bangkok, 10330, Thailand (Corresponding author: Orathai Chavalparit; e-mail: jayparon@gmail.com, orathai.c@chula.ac.th). Nantamol Limphitakphong is with the Research Unit of Environmental Management and Sustainable Industry, Chulalongkorn University, Bangkok, 10330, Thailand (e-mail: nantamoll@gmail.com). Premrudee Kanchanapiya is with the National Metal and Materials Technology Center, 114 Thailand Science Park, Pathumthani, 12120, Thailand (e-mail: premrudk@gmail.com). Thanapol Tantisattayakul is with the Faculty of Science and Technology, Thammasat University Rangsit Campus, Pathumthani, 12121, Thailand (e-mail: thanapolosk@hotmail.com). [1]-[3], permeable pavement [4]-[6], and rainwater harvesting [7]-[9]. Rainwater harvesting (RWH) is one of “Green infrastructure” technique that involving the design for the collection and storage of rainwater runoff from building roof as a non-potable source within domestic, commercial, institutional and drinking water industrial sectors. With the increasing demand in the water resource globally due to the extensively exploited of the water resource, this technique can be a promising alternative for water supply as well as for the improvement of storm water drainage systems. There are numerous practices of RWH around the world either by developed or developing countries. United States, Germany, Spain and Australia have implemented rainwater harvesting policies at different governmental levels which addition of economic incentives [10]-[13]. In Thailand, this technique has been taking a deep root for more than a century mostly in the rural area. For the urban area, this approach is not frequently applied due to a strong concern on air pollution which affecting the quality of rainwater in the city as compared to rural area. Rainwater harvesting system, however, is more economically feasible in higher water demand areas [14]. This study, therefore, aimed to make the assessment for the potential of rainwater harvesting in Bangkok, the capital city of Thailand by using the study building where the amount of water demand is high as a case study. Both the quantity of tap water reduction and economic feasibility from rainwater harvesting system were evaluated. As a result, the sustainable water resource management could help alleviate the problem of flooding which occurred more frequently during the rainy season and drought in the summer in Thailand. II. METHODOLOGY For the concept of rainwater harvesting, the rain falling on the roof is collected and passed through the filter system and stored in the rainwater tank. The collected water can be used for the replacement of the tap water utilization as shown in Fig 1. The model calculation for the amount of available rainwater in RWH system is demonstrated in Fig 2. Data input in this model also including the rainfall volume, roof area, rainwater collection tank capacity and water consumption rate for the building. Rainfall volume; R (m 3 /day) can be calculated by using rainfall data; H (mm) for every 3 hours a day; “n” during the year of 2015 - 2016 was gathered from Department of Meteorology and the roof area of the case study building; A (m 2 ) as Eq. 1 Assessing Potential of Rainwater Harvesting: Case Study Building in Bangkok Paron Monjaiang, Nantamol Limphitakphong, Premrudee Kanchanapiya, Thanapol Tantisattayakul, and Orathai Chavalparit International Journal of Environmental Science and Development, Vol. 9, No. 8, August 2018 222 doi: 10.18178/ijesd.2018.9.8.1105