23 Groundwater Flow Systems in the Desert Southwest

Thursday, 9 May 2002
1:00 PM - 4:00 PM

HYDRAULIC PROPERTIES OF PALEOZOIC CARBONATE ROCKS IN THE DEATH VALLEY REGION, NEVADA AND CALIFORNIA

Paper number: 23-5
Program: THEME SESSIONS
Time: 2:20 PM – 2:40 PM

Authors

Abstract

Paleozoic carbonate rocks are the principal bedrock aquifer in the Death Valley region of southeastern Nevada and California. The Amargosa Desert tracer test site (ATS) was constructed to determine hydraulic properties of Paleozoic rocks in the vicinity of the Nevada Test Site (NTS). Unpublished data from three pumping tests conducted in 1967 and 1975 at the ATS were analyzed in this study. These analyses indicated transmissivity of 5,800-6,700 m2/d, hydraulic conductivity of 240-280 m/d, and storativity of 0.002.

In five pumping tests conducted at the ATS and 2 other sites in the Death Valley region, observation-well drawdown consistently indicated larger values of hydraulic conductivity than pumping-well drawdown. From hydraulic conductivity obtained in these tests, a regression equation was developed that can be used to estimate cross-hole-scale hydraulic conductivity (Kch) for Paleozoic carbonate rocks throughout the region.

In 13 pumping tests, including those at the ATS, Kch of Paleozoic carbonate rocks in the NTS area ranged from 1.1 to 270 m/d. The log mean Kch in these analyses was 6.8 m/d. In the NTS area, there appears to be a relation between faulting and enhanced hydraulic conductivity, which likely exists for Paleozoic carbonate rocks throughout the Death Valley region.