Assessment of rainwater harvesting for household water demand in Lancang Island Kepulauan Seribu DKI Jakarta

Abstract Small islands often experience severe water demand due to limited freshwater sources, population growth, and climate changes. Rainwater harvesting, which efficiently supplements water sources by utilizing rooftops as collection surfaces, offers a promising solution. This research aims to analyze rainwater harvesting as an alternative source of freshwater supply in Lancang Islands, Kepulauan Seribu, Daerah Khusus Jakarta. A quantitative approach was used to calculate household water demand and rainwater harvesting potential. Primary data, including water demand per person and building roof areas, were obtained through field surveys and questionnaires. Secondary data on rainfall were sourced from meteorological records. Although the results show that rainwater harvesting cannot meet household water demand year-round, buildings with the largest catchment areas can significantly increase the effectiveness of rainwater harvesting, reaching up to three times the household water demand per month, with a total of 60.286 liters in January. Furthermore, the largest building types, which typically include multi-purpose buildings, schools, or non-private structures, can collect even more water and can be used collectively by the community. Rainwater harvesting can serve as an alternative to address freshwater scarcity on Lancang Island. Although this method cannot yet be the primary source of freshwater, it can significantly contribute to alleviating water shortages.