See more from this Division: Topical Sessions
See more from this Session: Isotopic Tracers in Deep Groundwater Basins
Abstract:
Stable isotopes of the water molecule in local precipitation, streams, and groundwater fall within a narrow range, indicating locally derived water as the source of recharge. In deeper wells, colder noble gas recharge temperatures suggest a component of recharge dating back thousands of years. Radiogenic 4-helium concentrations up to 4.0e-6 cc(STP)/g indicate contribution from deep groundwater sources in both deep and shallow wells.
These groundwater age and isotopic data indicate groundwater supplies in the El Verano area mostly originate from pre-development recharge and deep sources. Even the shallowest wells are remotely connected to local recharge processes. Water level data show declining trends with depth. Simulation of gas-liquid phase flow and transport of water, air, tritium, and 3-helium components is used to reconcile age data with groundwater level trends. Hydrostratigraphy of thin aquifers and thick aquitards having depth-decreasing permeability yields simulation results consistent with the data. In terms of groundwater age and isotopic signature, this shallow aquifer system behaves like a relatively deep basin.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. DE-AC52-07NA27344.
See more from this Division: Topical Sessions
See more from this Session: Isotopic Tracers in Deep Groundwater Basins