Water is the most fundamental resource in the design of a regenerative building. In conventional development, water is treated as an infrastructure service: it arrives through pipes from a distant source and leaves through pipes to a distant treatment plant, and the occupants pay for both services without any particular understanding of or connection to the water cycle that makes it all possible. This system is enormously convenient and enormously fragile. Droughts, infrastructure failures, contamination events, and the growing demands of expanding populations stress water systems in every region of the world.

A regenerative building takes a different approach. It harvests water from its own roof during rain events, stores it in cisterns sized to bridge the intervals between storms, filters it to potable quality on-site, uses it efficiently, and treats all resulting waste water on-site before returning it to the landscape. This approach creates a direct, quantitative relationship between the building and its local hydrology: the amount of water available is determined by how much rain falls on the roof. This is not a limitation; it is an invitation to understanding.

The complete water system for a regenerative building is covered in depth in Book 5 of this series, the Water Textbook. This chapter introduces the key concepts and design principles.