MINERAL WEATHERING AND GROUNDWATER FLOW IN OWENS VALLEY SPRINGS

The groundwater flow system in Owens Valley and the surrounding mountain blocks is complicated by extensive normal faulting associated with the western flank of the Basin and Range Province. In addition, the geology is characterized by clastic and carbonate sedimentary rocks cut by granitoid intrusions. We coupled field observations of temperature and conductivity with water stable isotopes to understand circulation patterns. In addition, we paired strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) with general geochemistry of groundwater discharging in springs to delineate sources of minerals and to better understand flow paths through inverse mass balance modeling.

Field observations and water stable isotope results suggest two types of groundwater. In the northern portion of the study area (near Bishop, CA), springs discharge lower temperature, lower TDS, isotopically lighter groundwater compared to the southern portion of the valley (Big Pine, Ca and south), with few exceptions. Inverse modeling results highlight the influence of both carbonate and granitoid rocks. Strontium isotope ratios vary throughout the study area and provide insight into the balance between granitoid, carbonate, and precipitation sources. Interestingly, spring water strontium isotope ratios are consistently lower than those previously observed in stream waters (Pretti and Stewart 2002). Pending additional analysis of strontium isotope ratios of rocks along potential flow paths will provide further insight into flow paths and weathering sources. Study results will help differentiate local and regional flow systems and provide further insights into the resilience of groundwater in the Owens Valley region.