DECIPHERING GROUNDWATER FLOWPATHS IN INDIAN WELLS VALLEY, SOUTHEASTERN CALIFORNIA, USA: EVIDENCE FOR AN INTERBASIN FLOW COMPONENT

In Indian Wells Valley (IWV), surface waters are scarce due to extreme aridity, and groundwater is the only source of water for consumptive and household use. Hence, a good understanding of groundwater circulation patterns is important for the development and effective management of the groundwater resource. Hydrochemical data from 1,368 water samples spanning more than 80 years were analyzed using cluster analysis, geochemical modeling and geographic information system (GIS), and used to decipher groundwater flowpaths in IWV. The chemical composition of the water samples in the area describe the changing chemistry of water in a regional flow system beginning with the dilute Ca-Na-HCO3 recharge waters of Sierra Nevada and ending with the Na-Cl brines around the China Lake playa. Cluster analysis results suggest the existence of five major water groups in the area. When plotted on the site map, these groups form distinct clusters, in which all major-ion concentrations increase progressively from Sierra Nevada to China Lake playa. This trend suggests a generalized easterly flow direction of groundwater. This result is also consistent with Basin and Range groundwater flow system as described by previous researchers. The distribution of water types from the southeastern part of the IWV, however, does not conform to this regional trend. The groundwater from that part of the IWV has distinctly different chemistry, which is statistically more similar to waters from the Kern Plateau area (in the high Sierra Nevada outside the local watershed), than to waters from the local watershed. The groundwater is low in total dissolved solids and interpreted to originate from fracture directed interbasin flow from Kern Plateau area. This finding contradicts with the present models for the hydrologic system in the IWV, which assume the basin is a closed system with recharge derived from precipitation in the local topographic drainage basin. However, this finding supports recent suggestions that a unique combination of interconnected faults exist in crystalline bedrock of the eastern Sierra Nevada, which may serve as conduits for interbasin flow. This type of flow could have an enormous impact on water rights and water supplies for this arid region.