1. Introduction

Water is life and a primary need of all living beings. Human beings also need water not only for survival but also for their multipurpose and ever increasing needs other than the basics. The amount of usable water on the Earth’s surface is continuously shrinking and becoming polluted due to various human activities in the name of development. When surface waters, as a primary choice, are being polluted daily, then underground water as a secondary option is continually being extracted in many parts of the globe while the negative impacts of this practice are ignored. In this context, a third option is investigated herein. Buildings of various occupancies are the only infrastructures in which human beings live or conduct various businesses safely and comfortably. For safe and comfortable living in buildings, even for a little while, there is need of water. Providing wholesome water in buildings is therefore a major concern in building development. For buildings, water is generally drawn from a public main running by the side of the building; in unavoidable cases, an independent water source, such as tube well, is used for withdrawing underground water. In many parts of the globe, both surface and groundwater is continually becoming limited due to natural calamities and manmade interventions; in contrast, the demand for building development is increasing with the increase in population and the quest for socioeconomic development. The development of buildings is therefore creating an increase in water demand, which cannot be met by the usual practices depending on the sources of conventional surface and groundwater. Against this backdrop, a third option is envisaged for managing the shortage of water for any building: The practice of rainwater harvesting has been found to be reliable where sufficient rainfall occurs and adequate catchment is available to collect rainwater. In this chapter, the circumstances invoking rainwater harvesting in buildings is discussed, and its history of practice—as well as the present scenario in the global perspective—are delineated. An introduction to buildings and the prospects and the constraints of using rainwater in buildings is also described.