Development of the San Fernando Basin Groundwater Flow Model

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by Shih-Huang Chieh, James M. Montgomery, Inc., Walnut Creek, United States,
Kelli A. Shuter, James M. Montgomery, Inc., Walnut Creek, United States,
Melih M. Ozbilgin, James M. Montgomery, Inc., Walnut Creek, United States,

Document Type: Proceeding Paper

Part of: Water Resources Planning and Management: Saving a Threatened Resource—In Search of Solutions

Abstract: This paper describes the development and calibration of the San Fernando Basin (SFB) groundwater flow model. The SFB is the largest groundwater basin in the Upper Los Angeles River Area (ULARA) a large alluvial valley with 205,700 acres of hill and mountain areas on all sides. The San Fernando Basin consists of 112,000 acres and comprises 91.2 percent of the total valley fill. The SFB is a water-table aquifer with a saturated thickness exceeding 1,000 feet near its center. A finite-difference groundwater flow model was selected for this site. The basin was discretized into 86-by-64 finite-difference mesh with four aquifer layers. Various boundary conditions were assigned to simulate faults and areas along valley fill boundary, as well as fluxes from the Los Angeles River, various spreading grounds, and mountain runoff. Voluminous amounts of data were available for this basin including about 1,100 well logs with well location, construction data, lithological data, and water-elevation data. The large amount of available data allowed for the inclusion of a high degree of hydrogeologic heterogeneity. Because of the amount of data, GIS and FORTRAN processing programs were used to manage the raw data, create model input files, and assist the calibration process. During development, the numeric model was used to further refine the conceptual model of the basin hydrogeology. The developed SFB groundwater flow model was successfully calibrated against field data for steady-state conditions and then transient conditions.

Subject Headings: Groundwater flow | Basins | Hydrologic models | Data processing | Calibration | Mathematical models | Hydrologic data | Finite difference method | North America | California | Los Angeles | United States

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