Use of δ¹8O and δD to Define Seawater Intrusion

by John A. Izbicki,

Document Type: Proceeding Paper

Part of: North American Water and Environment Congress & Destructive Water


On the basis of previous studies, more than 60 km² of upper aquifer system underlying the Oxnard Plain was believed to be intruded by seawater. Recent work has shown that there are sources of high-chloride water to wells other than seawater. In this study, δ18O and δD data were used in conjuction with chloride data to identify the source of high-chloride wat to wells and redefine the areal ext of seawater intrusion. On the basis of these data, 14 km of the Oxnard aquifer and 8.5 km² of the Mugu aquifer within the upper aquifer system are intruded by seawater. In some areas, the seawater front is preceded by high-chloride water derived from fine-grained deposits within the Oxnard and Mugu aquifers. In much of the area formerly believed to be intruded by seawater, ground water was found to be fresh.

Subject Headings: Salt water intrusion | Sea water | Chloride | Groundwater quality | Wells (water) | Hydrologic data | Groundwater

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