Hydrogeologic investigation of a shallow aquifer system with emphasis on precipitation induced recharge, lower Borrego Canyon Wash, Irvine, California

The hydrogeology within the lower portion of the Borrego Canyon Wash, Irvine, California, consists of an alluvial and heterogeneous bedrock aquifer system. Initial assessments of the hydrogeology showed heterogeneous lithology, extreme variance in the aquifer properties, and uncertainty to aquifer boundary conditions. During a long-term, multiple well, aquifer test, significant fluctuation of groundwater elevations were observed at various locations across the site.; Precipitation-induced recharge had pronounced effects on nearly all wells within the aquifer test area. The precipitation events provided higher stresses in the aquifer than could be achieved with groundwater extraction alone. Therefore, the real time monitoring of groundwater fluctuations and precipitation provided reliable insight into how the aquifer systems and different hydrogeologic zones interact. These data, in conjunction with the long-term aquifer test, enabled the identification of hydraulic barriers and hydrogeologic zones within the aquifer systems. Twelve hydrogeologic zones were identified, 2 within the alluvial aquifer and 10 within the bedrock aquifer.; This investigation shows that within a similar shallow aquifer system, long-term water elevation monitoring during precipitation events may provide the best data to characterize a complex heterogeneous aquifer system.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows MediaPlayer or RealPlayer.