OCWD had determined that information on the piezometric level and water quality of each aquifer layer was required to optimize management of the recharge, storage, and recovery of groundwater.
A cost analysis indicated that for 10 zones through a depth of 1,500 ft, the Westbay System instrumentation would result in a total cost 55% to 65% lower than that for clustered wells or two five-well nests
The increased data density from the Westbay System multilevel wells provides OCWD with an unprecedented definition of groundwater flow and variations in water quality.
California residents depend on groundwater for drinking water supply
The Orange County Water District (OCWD) in Southern California, USA, is responsible for supplying clean water to more than 2 million residents in a 380-mi2 [970-km2] service area. The facilities have the capacity to recharge approximately 250,000 ac-ft [3.1x103m] of water per year by percolation along the channel of the Santa Ana River and off-channel basins.
Groundwater supplies more than 60% of the total water demand in the area and managing this groundwater resource is the OCWD's number one priority.
Water level and quality data required to optimize groundwater management
Management of groundwater over a large area is an involved process. Each year, 0CWD monitors groundwater levels, production, and recharge quantities to evaluate groundwater storage changes in the basin, replenishes the basin, and conducts an assessment program to pay for operating expenses and the cost of the imported replenishment water. The district has an ongoing effort to increase available local water supplies through innovative programs such as expanding the capacity of existing percolation facilities, treating poor-quality water to make it useable, and reclaiming water.
The geology of the groundwater basin consists of alternating layers of uncemented fine- and coarse-grained sediments in a synclinal trough that plunges toward the northwest. Wellbores typically penetrate 10 to 15 different water-bearing layers over a depth of up to 1,500 ft 1460 mj. By the mid-1980s, 0CWD had determined that information on the piezometric level and water quality of each aquifer layer was required to optimize management of the recharge, storage, and recovery of groundwater.
Three methods of accessing the aquifer layers were considered:
- Cluster of separate wells, with each well completed in a separate zone
- Nest of wells with up to five well casings, each completed in a separate zone, in a single borehole
- Multilevel well using the Westbay System for groundwater monitoring