Modeling Saltwater Intrusion Control Measures in the West Coast Basinby Donald Schroeder, Camp Dresser and McKee Inc, Ontario, United States,
Bruce Jacobs, Camp Dresser and McKee Inc, Ontario, United States,
Abstract: In the 1960's and 1970's the West Coast Basin Barrier was constructed to protect tha major coastal groundwater basin from further salt water intrusion, which had been occurring as a result of increased inland pumping. The barrier consists of a line of 144 injection wells pumping an average of 27,000 acre-ft/year (24 mgd) to maintain a pressure ridge of sufficient head to block the intrusion of salt water. Prior to full operation of the barrier, significant quantities of saline water had migrated beyond the barrier line. Chloride concentrations in these inland plumes exceed an acceptable level of 250 mg/1, affecting an estimated 240,000 acre-ft of stored groundwater, and a number of wells have had to be removed from service. Continued migration of the plumes jeopardizes additional wells for several water systems and threatens the ability to use the basin for reserve storage. Following an extensive study of the barrier effectiveness in 1987-1989, several of the major impacted agencies undertook an additional study of management alternatives to control and mitigate the inland chloride plumes. A range of management alternatives was developed. In order to provide technical information to allow the alternatives to be compared, a numerical model was developed. The basin was modelled using CDM's groundwater flow model, DYNFLOW, and companion contaminant transport model, DYNTRACK. DYNFLOW uses a Galerkin finite element technique with linear 3-d elements to simulate three dimensional groundwater flow in heterogeneous anisotropic, confined and unconfined aquifers.
Subject Headings: Hydrologic models | Salt water intrusion | Water pollution | Basins | Water quality | Wells (water) | Water supply
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