Tracing waste-water in river and ground water of Orange County using boron211 isotopes and general geochemistry

摘要

Surface water runoff within the Santa Ana River (SAR) watershed is generated from211u001ea variety of sources, including a mountain snowmelt, urban waste-water discharge, 211u001eand dairy feedlots. During summer baseflow periods, the persistent flow of 211u001eapproximately 200 cubic feet per second (cfs) consists almost entirely of 211u001etertiary-treated waste-water from upstream urban discharge. The Orange County 211u001eWater District (OCWD) artificially recharges the majority of flow from the SAR 211u001eduring high and low flow periods into the Forebay region to augment groundwater 211u001epumping demands. Proposed regulations for reclaimed water recharge into portable 211u001euse aquifers have direct impact on how OCWD manages groundwater recharge from the 211u001eSAR. Knowledge of how much treated waste-water recharges into the Forebay area of 211u001ethe Orange County Groundwater Basin has direct benefit to future management and 211u001eregulatory activities. This project attempted to trace the inorganic components 211u001eof waste-water dissolved in the SAR and local groundwater in the Forebay by 211u001eapplying geochemical and boron isotopic systematics. The objectives were to 211u001echaracterize the chemical and boron isotropic compositions of recharged surface 211u001ewater and groundwater, to delineate typical mixing end-members, and to examine if 211u001erecharge water from the SAR has a different isotopic signature relative to non-211u001eanthropogenically-influenced groundwater. The overall goal is to test whether a 211u001ecombination of boron isotopes and water chemistry will provide an accurate means 211u001eto quantifiably distinguish waste-water from non-waste water sources in surface 211u001eand groundwater of the Forebay.