A study conducted by NRDC and the University of
California, Santa Barbara, A Clear Blue Future, found that
implementing green infrastructure practices that emphasize
on-site infiltration or capture and reuse had the potential
to increase local water supplies by up to 405,000 acre-feet
per year by 2030 at new and redeveloped residential and
commercial properties in Southern California and the San
Francisco Bay area. This represents roughly two-thirds of the
volume of water used by the entire city of Los Angeles each
year.

These water savings translate into electricity savings
of up to 1,225,500 megawatt-hours—which would decrease
the release of carbon dioxide (CO2
) into the atmostphere
by as much as 535,500 metric tons per year—because more
plentiful local water reduces the need for energy-intensive
imported water. And, perhaps most importantly, these
benefits would increase every year.13

This analysis led to the inclusion of green infrastructure
as a strategy in California’s “Land Use Planning and
Management,” signifying the state’s recognition of green
infrastructure’s value in water supply planning in the State
of California.14 Green infrastructure was also included as
a strategy in California’s Global Warming Solutions Act
of 2006 (AB 32), in recognition of its ability to to reduce
energy demands associated with the transport of water.15
Similar benefits, at least in terms of water supply quantity,
are available throughout the country. An NRDC report on
rainwater capture released at the same time as this report
demonstrates that the volume of rain falling on rooftops
in eight different cities, if captured in its entirety, would
be enough to meet the annual water needs of 21 percent
to 75 percent of each city’s population. Even under more
conservative assumptions, the study demonstrated that each
of the cities modeled could capture hundreds of millions
to billions of gallons of rainwater each year—amounts
equivalent to the total annual water use of tens of thousands
to hundreds of thousands of residents.16


http://www.nrdc.org/water/pollution/rooftopsii/files/rooftopstoriversII.pdf