Open AccessMeasurement of unsaturated hydraulic conductivity in the Bandelier Tuff at Los Alamos
Author(s) -
James L. Conca,
T.J. Mockler
Publication year - 1995
Language(s) - English
Resource type - Reports
DOI - 10.2172/245577
Subject(s) - groundwater recharge , flux (metallurgy) , national laboratory , water content , hydraulic conductivity , vadose zone , hydrology (agriculture) , moisture , arid , heat flux , geology , mineralogy , environmental science , soil water , chemistry , soil science , aquifer , heat transfer , physics , geotechnical engineering , groundwater , thermodynamics , paleontology , organic chemistry , engineering physics
Hydraulic conductivities, K, were experimentally determined as a function of volumetric water content, {theta}, in Bandelier Tuff cores from Los Alamos, New Mexico. These data were used to determine the feasibility of applying a new unsaturated flow technology (UFA{trademark}) to further hydrologic studies of tuffaceous rocks at Los Alamos. The K({theta}) relationships for eight cores of Bandelier Tuff from boreholes AAA and AAB were measured using the UFA and, together with their in situ water contents, were used to determine transient water flux into these samples at the time of sampling. If the system is at steady-state, then these flux values correspond to the recharge through those points, a situation often encountered in semi-arid to arid regions such as Los Alamos and other sites in the western United States. Samples AAA 9956, AAB 0011, AAB 0012 and AAB 0040 exhibited fluxes of 6 x 10{sup -8} cm/s, 4.8 x 10{sup -7} cm/s, 2.8 x 10{sup -7} cm/s and 2.4 x 10{sup -8} cm/s, respectively, indicating significant flux. Samples AAB 0063, AAB 0065, AAB 0072 and AAB 0081 had very low water contents suggesting fluxes less than 10{sup -10} cm/s, and appear to be close to their residual water contents. Assuming that the samples AAB 0063, AAB 0065, AAB 0072 and AAB 0081 were not accidentally dried out during handling, these results imply that these samples have zero recharge and that redistribution of moisture at these horizons is controlled more by vapor diffusion than by advection. The vapor diffusivities in these cores can be determined using the new UFA gas permeameter. Samples AAA 9956, AAB 0011, AAB 0012 and AAB 0040 appear to be controlled by advection