Geohydrology of the Big Bear Valley

Project Chief: Alan Flint

The Big Bear Valley ground-water basin underlies Bear Valley and is bounded by crystalline rocks of the San Bernardino Mountains. Precipitation in the valley provides recharge to the underlying ground-water basin. Big Bear Lake, in the western portion of the valley, is filled from runoff from numerous creeks that drain the valley floor. Baldwin Lake, typically dry, lies in the northeastern portion of the valley. Average annual precipitation in the valley ranges from 30 inches on the western edge of the valley to 15 inches on the eastern edge of the valley. The population of the Big Bear area has increased from about 12,000 in 1980 to about 22,000 in 2004. The water supply for the Big Bear area is produced mainly from springs on the periphery of the ground-water basin and wells drilled within the ground-water basin. The Big Bear area has been in a drought for 6 years, resulting in less recharge than average to the aquifer system and increased pumping. As the drought has continued, spring flow and well yields have decreased. In June 2003, the City of Big Bear Lake Department of Water and Power (DWP) Board of Commissioners declared a water shortage emergency for the DWP service area in the Big Bear Valley. The Big Bear City Community Services District (CSD) has limited new water connections and initiated water restrictions in response to the drought. To help meet water demand, the local water agencies have constructed new wells and are considering artificial recharge with reclaimed wastewater. To better manage the ground-water resources in the Big Bear Valley, there is a need to better understand the geohydrology of the ground-water basin.

The objectives of the first phase of the study are (1) to define the depth and structure of the Big Bear Valley ground-water basin and (2) to estimate the quantity of rainfall and runoff that contributes recharge to the ground-water basin. Future phases of the study may include defining the source(s) and the age(s) of ground water in the basin and developing and calibrating a ground-water flow model to help understand the ground-water flow system. The study will develop a greater understanding of the hydrology of the Big Bear Valley ground-water basin and will allow the Big Bear City Community Services District to better manage and utilize the ground-water resources.

The study develops a greater understanding of the hydrology of the Big Bear Valley ground-water basin and allows the Big Bear Valley Community Services District to better manage and utilize the resource. The study will address the effects of urbanization and suburbanization on water resources and the effects of climate on water resources, issues 1 and 7 from the Strategic Directions for the Water Resources Division, 1998–2008.

In this study, geophysical data are used to help define the depth and geologic structure, Interferometric Synthetic Aperture Radar (InSAR) data will be collected and analyzed to determine if land subsidence is occurring and to locate possible buried faults, and a rainfall-runoff model will be used to estimate the quantity of rainfall and snowfall that contributes to recharge in the basin. Selected wells will be sampled and analyzed for chemical and isotopic data to determine if there is a significant variation in the source and age of water in the basin. Significant differences in the source and age of the water will prompt sampling the basin in greater detail.

Contact Information

Alan Flint
Office phone: 916-278-3000

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