Potential of traditional domestic rainwater harvesting systems: current trends and future directions

Although the potential of traditional domestic rainwater harvesting systems (RWHSs) is easily determined, objective knowledge is required to determine their sustainability or scientific validity. We aimed to broadly review recent trends and emerging opportunities for research on the potential of RWHSs in the global context. We reviewed three types of representative RWHSs: water cellars, stepwells, and qanats. In total, 16 potential categories were defined. First, to date, 50% of the categories of potential have been demonstrated but are not considered beneficial, have been proven only in limited locations, only in limited sampling sets, or are theoretical. Second, whether the involvement of other disciplines has resulted in an expansion of the research scope or whether a particular potential has not been comprehensively explained remains to be determined by researchers. Third, potential that has emerged in the 21(st) century is not beyond our imagination such as tourism potential and ecological potential. Therefore, researchers should actively explore and incorporate new innovative technologies with RWHSs to explore new potential. The findings of this study offer a viable research framework for investigating the evolution of the discipline and contribute to the development of critical thinking in the analysis of the potential of RWHSs.