Our buildings and homes could capture all water we need on a daily basis. A great example of rainwater harvesting can be found at the Langston Brown Community Center and High School in Arlington, Virginia. The community center has two 24-foot-tall 11,000-gallon cisterns that store rainwater.
The tank at the front of the school is covered with panels, and fits seamlessly into the overall design of the building.
The building captures 280,000 gallons of water a year. Regrettably, the rainwater is only used for onsite irrigation, sidewalk washing, and other non-potable uses. However, the center does have waterless urinals which result in a 23% reduction in potable water use.
Nearby in Maryland, the Philip Merrill building (headquarters of the Chesapeake Bay Foundation), captures even more rainwater — 402,461 gallons a year — the rain provides almost all the water used in the building.
All the details of the green elements of the community center can be found here.
A good book about rainwater harvesting case studies is Design For Water by Heather Kinkade-Levario.