Groundwater hydrochemical facies, flowpaths and recharge determined by multivariate statistical, isotopic and chloride mass-balance methods
Multivariate statistical methods (MSMs) applied to groundwater chemistry provide valuable insight into the main hydrochemical species, hydrochemical processes, and water flowpaths important to groundwater evolution. This hypothesis is supported by the examination of available chloride, oxygen-18, hydrogen-2, carbon-13, and carbon-14 data from the region. The MSMs of principal component analysis (PCA) factor analysis (FA), correspondence analysis (CA) and k-means cluster analysis (KMCA) were sequentially applied to major ion chemistry from 209 different groundwater sampling-locations in the Amargosa Desert. The FA reduces the number of variables describing the system and finds relationships between major ions. The KMCA of the reduced system produced objective hydrochemical facies, which are independent of, but in good agreement with, lithological data. The derived factors and hydrochemical facies are innovatively presented on biplots, revealing composition of hydrochemical processes and facies, and overlaid on a digital elevation model, displaying flowpaths and interactions with geologic and topographic features in the region. In particular, a distinct groundwater chemical signature is observed beneath and surrounding the extended flowpath of Fortymile Wash, presenting some contradiction to contemporary water levels along with potential interaction with a fault line. The signature surrounding the ephemeral Fortymile Wash is believed to represent the relic of water that infiltrated during past pluvial periods when the amount of runoff in the wash was significantly larger than during the current drier period. Furthermore, chloride mass-balance was applied to drill cuttings to determine local infiltration rates and dates, which corroborate the previous analyses.^
Woocay, Arturo, "Groundwater hydrochemical facies, flowpaths and recharge determined by multivariate statistical, isotopic and chloride mass-balance methods" (2008). ETD Collection for University of Texas, El Paso. AAI3320185.