UWM Plan - Municipal Water District of Orange County

Section 3
Water Sources and Supply Reliability
La Habra Groundwater Basin Geology
From a structural geology standpoint, the La Habra Basin area is dominated by the
northwest trending La Habra Syncline (a U–shaped down–fold) which is bounded on the
north by the Puente Hills and on the south by the Coyote Hills. The fold is a naturally
occurring trough, or valley, where significant quantities of groundwater have
accumulated over the past 150,000 years. The La Habra Groundwater Basin consists of
four major formations, which include bearing zones or aquifer units. These are the
Alluvium, the La Habra Formation, the Coyote Hills Formation, and the San Pedro
Formation.
Water levels of wells in the La Habra Formation have been measured between 100 and
200 feet below ground surface across the La Habra Basin area. Water levels in wells of
the Coyote Hills Formation have been measured at about 120 feet below the ground
surface. Pressure levels of confined groundwater in wells of the San Pedro aquifer zone
range from about 100 to 200 feet below ground surface.
Currently, this non-adjudicated basin is serving the City of La Habra. The estimated longterm
groundwater supplies from the basin have ranged from 3,700 AFY to 4,500 AFY;
however, the historical City of La Habra extraction rate is approximately 1,074 AFY
(averaged over the past 15 years). The City plans to utilize the additional groundwater
supply by increasing the capacity on the existing Idaho Street Well.
Full development of the La Habra Basin could eventually supply up to 40% of the City’s
current water demands. The City of La Habra currently plans to double production
capacity for the Idaho Street Well from 1,200 to 2,400 AFY, which will increase reliance
on local sources from 11% to 22% of total demands. Table 2-12 shows projections for
water extracted from the La Habra Groundwater Basin.
3.3.4. Main San Gabriel Basin (California Domestic Water Company)
The Main San Gabriel Basin lies in eastern Los Angeles County. The hydrologic basin or
watershed coincides with a portion of the upper San Gabriel River watershed, and the
aquifer or groundwater basin underlies most of the San Gabriel Valley.
Surface area of the groundwater basin is approximately 167 square miles and has a fresh
water storage capacity of the basin is estimated to be about 8.6 million acre-feet.
The physical groundwater basin is divided into two main parts, the Main Basin and the
Puente Subbasin. The Puente Subbasin, lying in the southeast portion is hydraulically
connected to the Main Basin. However, it is not the legal jurisdiction of the Main San
Gabriel Basin Watermaster, and is thus considered a separate entity for management
purposes.
Municipal Water District of Orange County
2010 Regional Urban Water Management Plan
Final
3-30