Desert Living
Cisterns and Rainwater Harvesting
(Reprinted from the October-December, 2008, Rincon Group Newsletter)
by Charles J. Cole and Carol R. Townsend
as printed in Restoring Connections, the newsletter of Sky Island Alliance
Water is perhaps the scarcest and most precious lifesustaining
resource in the desert and desertgrassland
seas that surround the Sky Islands. With
human population growth increasing, particularly in the
Phoenix and Tucson areas, but also in nearby areas such as
Las Vegas, demand for water will outstrip supply in a matter
of years. Imagine the stampede for bottled water on the day
people open their taps and nothing flows, or the costs to
obtain reliable additional tons of potable water from...where
and how? The well-known problems of flooding in New
Orleans from Hurricane Katrina and the lack of preparedness
for that event make us wonder what preparedness there is
in the arid Southwest for the opposite problem the day when
the water runs out.
Homeowners, architects, builders, and governing bodies
can effectively address this problem now by encouraging
capture of rainwater off roofs and other places and storing
it in large tanks or cisterns. With proper design,
implementation, and treatment a single house can have enough
pure water for all of its household uses, in the absence of
town water or a well. For example, at our house near Tucson
our large cistern could have provided 100% of our household
needs for two of the last three years, and that includes
maintaining a swimming pool. Our builder designed the system
by modifying one described by PeterL.Pfeifferin Fine
Homebuilding (2001, No. 142, Oct./Nov.issue, pp. 84—89).
The basics of our system are as follows. Rain flows down
the metal sloping roof to gutters, then downspouts take the
water into underground pipes. These pipes feed it through
two filters and then into the cistern, of approximately 26,000
gallon capacity, buried, of swimming-pool-like construction,
and covered with a cement top.
When water is needed in the house, a pump sends it out
of the cistern, through a 20-micron filter and into a pressure
tank, operating automatically, similar to the pump system in a
well. From there, it goes through three more filters (a carbon
filter, 5-micron sediment filter, and 10-micron carbon-block
filter) and passes over an ultra-violet light to kill possible
biological contaminants, then into the house. For the water
we drink and use for cooking, we also have a small reverse
osmosis filter system under the kitchen sink. Annual
maintenance of the system requires periodic hosing down of
the pre-cistern filters and change of the other filters and UV
light bulb.
Although our system was easily installed as part of the
original house construction, retrofitting to existing buildings is
possible. It is even possible to provision several buildings off
a large centralized system or off several smaller ones, as
some resorts do in Australia. Some people install inexpensive
above-ground water storage tanks, which can be unsightly
but also can be hidden behind vine-covered trellises or fences,
or within a decorative faux-rock structure such as exhibitors
use for natural-looking displays at the Arizona-Sonora Desert
Museum.
Anybody who is seriously interested in learning more about
our system is invited to call 520-743-3402 or email
cole@amnh.org for an appointment to see it. We are not
selling anything and have no personal interest other than to
spread the word. Any interested person who sees our system
is encouraged to go forward and build a better one and
continue to spread the word. The potential is great, as is the
need. Arizona has the opportunity to develop and provide
leadership in this important area.
