AUTHOR:
 MONO AUTH: Perina, Tomas
MONO TITLE: Geophysical and hydraulic modeling of the Winchester Basin,
            Southern California
 CORP INFO: University of California, Riverside; Riverside, CA; United
            States
            Master's
    SOURCE: 221
REFERENCES: 22
      YEAR: 1993
  LANGUAGE: English
  PUB TYPE: Thesis, Monographic
  ABSTRACT: The Winchester Basin lies between the low-TDS (Total Dissolved
            Solids) Hemet and San Jacinto basins on the east and high-TDS
            Menifee and Perris basins on the west. The transitional role of
            the Winchester Basin is an important link in the water resources
            management in western Riverside County. The basin configuration
            is inferred from inversion of gravity measurements covering of
            the sedimentary fill hyperbolically with depth. an area of 154
            km2. Density is assumed to increase Estimate of the sediment-
            basement interface is mainly constrained by interpretation of
            eight seismic refraction profiles. A circular local gravity
            anomaly located north of the basin, caused by a gabbro
            intrusion, was removed from the residual anomaly before the
            determination of depths to the basement. Both gravity and
            seismic data indicate the Winchester Basin is an east-west
            elongated trough with a maximum depth of 300 m. The trough
            connects to the Hemet Basin on the east, and to the Perris Basin
            onthenorthwest. The Winchester Basin appears to be separated
            hydrologically from the Menifee Basin on the south-west. MODFLOW
            is adopted to model the flow pattern for the years 1991-1992.
            Models of one layer, two layers, and two layers with an
            intervening confining layer have been made for various recharge-
            discharge rates. Based on water well-levels, constant-head
            boundaries were imposed at interfaces with other basins and a no-
            flow boundary was imposed at the contact with crystalline rocks.
            Some temperature logs in the Winchester Basin suggest
            groundwater flow outward from the central part, consistent with
            the flow modelling results. Near a newly established pond, the
            temperature logs clearly indicate leakage of the pond water. Two
            logs in the western part of the Hemet Basin suggest there could
            be a two-aquifer system, an inference unsubstantiated by an
            earlier geophysics study. Temperature logs in the Menifee Basin
            clearly indicate the existence of a two-aquifer system, as
            substantiated by well logs and hydraulic head differences. The
            Menifee Basin, however, is not included in my modelling study.
DESCRIPTOR: aquifers; basement; California; data processing; depth;
            discharge; flows; gabbros; geophysical surveys; gravity
            anomalies; ground water; hydrology; igneous rocks;
            interpretation; intrusions; layered materials; models; plutonic
            rocks; recharge; refraction methods; seismic profiles; seismic
            stratigraphy; seismic surveys; Southern California; surveys;
            temperature; temperature logging; United States; well-logging;
            Winchester Basin