Agenda - City of Santa Monica

Beyond the additional local groundwater opportunities described above, potential exists
for joint-development of nearby under-utilized groundwater basins, including the
Hollywood and Central Basins. These are multi-jurisdictional opportunities that will
require coordination between the City and the Los Angeles Department of Water and
Power and/or the City of Beverly Hills. Given the nature of institutional-related projects,
these opportunities are considered as more long-term water supply options and are not
included in the list of potential new groundwater opportunities available to the City to
meet its self-sufficiency goal by 2020.
Rainwater Harvesting and Stormwater Capture
Rainwater harvesting (the capture and onsite use of rainwater for landscape irrigation
purposes) offers minimal opportunity as an additional water supply within the City.
Santa Monica’s Mediterranean climate is characterized by seasonal rainfall, with the
majority of rain falling in the winter months of November through March. Conversely,
landscape water demands are highest in the warmer, drier months of April through
September. Analyses were performed to evaluate and compare the potential for
rainwater harvesting based on average monthly precipitation data and monthly
landscape water demand for residential and commercial customers.
Results of the above analysis indicate that the potential for rainwater harvesting as a
supply option in Santa Monica is limited by the large size of cisterns and customers’
motivation to install them. For most residential and commercial customers in the City,
space is limited; therefore, it was assumed customers would install no more than 500
gallons of rain harvesting capacity. A cistern of this size is depleted quickly, even in the
wetter winter months. In the drier summer months, rainwater supply is minimal, and
when available, landscape irrigation demand far exceeds the capacity of the cistern
therefore depleting this supply rapidly. Residential cistern installation, even with a
rebate of $1,000 per cistern, has been minimally accepted by the City’s customers.
Accordingly, it is estimated that the rainwater harvesting incentive program may provide
only 1-2 AF per year.
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