| PVPA
operates spreading facilities on about eleven hundred acres of
land along the San Antonio and Thompson Creeks for the purpose
of recharging the six underlying basins. The overlying land of
the basins encompass a nineteen square mile area bounded on the
north by the San Gabriel Mountains, by the San Jose Fault on the
east and south, the San Jose Hills on the southwest and a surface
water divide on the northwest.
The area receives
runoff from several canyons in the San Gabriel Mountains, including
San Antonio Canyon, Thompson Canyon, Live Oak Canyon and a number
of smaller canyons. Flood control reservoirs at the base of the
major canyons intercept runoff for release to flood control channels,
check dams and spreading ponds; the spreading grounds act as a
sponge to allow storm waters to percolate into the under-ground
basins.
Today ground water recharge occurs primarily at the San Antonio
Creek Spreading Grounds and the Thompson Creek Spreading Grounds.
These grounds, operated by the Pomona Valley Protective Association,
and adjacent facilities operated by the Flood Control Division
s of the San Bernardino County Department of Public Works and
the Los Angeles County Department of Public Works serve as the
major source of groundwater recharge in the Pomona Valley. Other
sources of recharge include the City of Pomona’s Pedley
Spreading Grounds and percolation of precipitation throughout
the area
Water levels in the
various basins exhibit large fluctuations over the course of a
year. In the canyon and Upper Claremont Heights Basins, water
levels may vary 100-150 feet during water levels fluctuate less
than 100 feet per year and do not appear to be greatly influenced
by recharge from the Upper Claremont Heights Basin. The Pomona
Basin has no direct surface recharge. As a result, water levels
are much lower than in the adjacent basins, but are more stable.
Water levels rise only when there is significant subsurface inflow
following wet years.
Over the past 91 years the Association has captured approximately
402,000 acre-feet, or 130.9 billion gallons of water. Through
the use of diversion structures on PVPA land this water has been
percolated back into the underground aquifers to be pumped out
as needed at well sites serving the various water purveyors in
the area.
One of the more outstanding examples of water conservation to
be found in this area is the operation of these spreading grounds.
It is through the continuing efforts of the Pomona Valley Protective
Association that today we can capture water that would otherwise
go to waste.
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