BOX 2-1

Groundwater Resources and Earthquake Hazards in the Los Angeles Basin

Periodic earthquakes and omnipresent water scarcity are two of the greatest challenges faced by Greater Los Angeles. Groundwater from the Los Angeles Basin supplies much of the drinking water for the area. As part of a cooperative project with the Water Replenishment District of Southern California and the Los Angeles County Department of Public Works to map the faults and the strata of the basin, the USGS drilled more than 30 monitoring wells. Scientists from the Geology Discipline and WRD were involved. They examined issues such as the rates of recharge of water infiltrated into groundwater from spreading ponds, and saltwater intrusion into freshwater aquifers along the coast.

The project resulted in new interpretations of the basin, including the recognition of ongoing tectonic deformation throughout most of the past several million years that has impacted the geometry and character of the sediments. These faults provide potential pathways for vertical migration of seawater and surface contaminants into the producing aquifers. This new framework should prove valuable in the design and operation of aquifer recharge projects, improve operations of seawater barriers, and identify areas of aquifer vulnerability. Overall, these efforts provided crucial information for sustainably managing the area’s groundwater supply while also locating areas especially susceptible to earthquake shaking.

SOURCE: USGS Fact Sheet 086-02. Available online at

It is important to note that the USGS Disciplines evolved somewhat separately with different missions and organizational structures, as well as different clients. Therefore it is unrealistic to expect full integration of the various Disciplines. Full integration refers to the idea that you might make water resources or some central theme “the organizing principle for everything.” However, one cannot reorganize the federal government to align each agency with every priority; hence entities must learn the arts of coordination, cooperation, and collaboration on complex objectives over a sustained period of years.

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