IDENTIFICATION OF POSSIBLE GROUNDWATER FLOW PATHS WITHIN THE DEATH VALLEY REGIONAL GROUNDWATER FLOW SYSTEM USING HYDROGEOCHEMISTRY AND MULTIVARIATE STATISTICS

Integrating groundwater flow and geochemistry can help identify groundwater sources, provide quantitative estimates of groundwater recharge, and improve predictions of contaminant fate and transport in groundwater systems. Understanding groundwater flow paths in and around the Nevada Test Site (NTS) is important due to the possible migration of contaminated groundwater from the NTS to the neighboring communities. Greater than 100 samples from well installations, as well as spring water discharge, have been collected from Pahute Mesa, Oasis Valley, the NTS, Ash Meadows/Amargosa Desert, Death Valley, the Spring Mountains, Amargosa Valley, and Nellis Air Force Range for trace element and major solute analyses. Multivariate statistics, such as Principal Component Analysis (PCA) and Cluster Analysis, were used to reduce the large amounts of geochemical data in order to decipher patterns within the data that otherwise might not be observed. ArcView Geographical Information Systems was also used to interpret the large amounts of sample data. It is possible, that the multivariate statistical results of the trace elements, as well as the rock-inherited aqueous geochemical patterns, can be used to 1) partition the groundwater into different flow systems and 2) provide a better understanding of the major geochemical processes responsible for the variability in the geochemistry within these systems. Current statistical analyses on the major solute data have resulted in three different groupings of groundwater chemical compositions consistent within the region. These groupings consist primarily of volcanic water, carbonate water and a combination of both volcanic and carbonate waters. Groundwater composition is also influenced by the geochemical composition of alluvium and the downward interbasin flow from alluvium into the waters of volcanic, carbonate, and/or volcanic-carbonate mix. These analyses were expanded to include a large group of tracer elements. The results will improve our understanding of important natural geochemical processes, such as the partitioning of groundwater into different flow systems, rock-water interactions of trace elements along predetermined flow paths and redox reactions.