WRIR 01-4210: Hydraulic-Property Estimates for Use With a Transient Ground-Water Flow Model of the Death Valley Regional Ground-Water Flow System, Nevada and California
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The Death Valley region encompasses an area of about 43,500 km2 in southeastern California and southern Nevada, between latitudes 35° and 38° 15' north and longitudes 115° and 117° 45' west. The study area is underlain by Quaternary to Tertiary basin fill sediments and mafic lava flows, Tertiary volcanic, volcaniclastic, and sedimentary rocks, Tertiary to Jurassic granitic rocks, Triassic to Middle Proterozoic carbonate and clastic sedimentary rocks, and Middle Proterozoic igneous and metamorphic rocks. As a result of several episodes of tectonic activity, rocks in the Death Valley region are faulted extensively. The hydraulic-properties database was compiled to support regional-scale ground-water flow modeling in the Death Valley region.
The DVRFS consists of interconnected hydrographic basins. Hydraulic connection between basins most commonly is maintained through unconsolidated sediments that were deposited across low topographic divides between the basins. Deep interbasin flow beneath valley floors and adjacent mountains and hills occurs primarily through fractured Paleozoic carbonate rocks.
Within the DVRFS, faults and related fractures are the largest influence on ground-water flow through bedrock aquifers. Faults disrupt stratigraphic continuity, which can divert water in regional circulation to subregional and local outlets. Less important than structure, but also an influence on ground-water flow is the lithology of rocks along flow paths.
Eleven HGUs were recognized in the DVRFS for the purpose of studying the distribution of hydraulic properties. Hydraulic properties were compiled and organized by these HGUs. Analyses also were performed to examine the relation between hydraulic conductivity and depth. Intuitively, hydraulic conductivity should decrease with depth as confining pressures seal fractures and faults and compress sedimentary units. ANCOVA indicate that depth is a significant factor in the variation of hydraulic conductivity, but the estimates can still vary a great deal at a given depth.
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