Application of flowmeter and depth-dependent water quality data for improved production well construction

Ground water production wells commonly are designed to maximize well yield and, therefore, may be screened over several water-bearing zones. These wat er-bearing zones usually are identified, and their hydrogeologic characteri stics and water quality are inferred, on the basis of indirect data such as geologic and geophysical logs. Production well designs based on these data may result in wells that are drilled deeper than necessary and are screene d through zones having low permeability or poor-quality ground water. In th is study, we examined the application of flowmeter logging and depth-depend ent water quality samples for the improved design of production wells in a complex hydrogeologic setting. As a demonstration of these techniques, a fl owmeter log and depth-dependent water quality data were collected from a lo ng-screened production well within a multilayered coastal aquifer system in the Santa Clara-Calleguas Basin, Ventura County, California. Results showe d that the well yields most of its water from four zones that constitute 58 % of the screened interval. The importance of these zones to well yield was not readily discernible from indirect geologic or geophysical data. The fl owmeter logs and downhole water quality data also show that small quantitie s of poor-quality water could degrade the overall quality of water from the well. The data obtained from one well can be applied to other proposed wel ls in the same hydrologic basin. The application of flowmeter and depth-dep endent water quality data to well design can reduce installation costs and improve the quantity and quality of water produced from wells in complex mu ltiple-aquifer systems.