INTERBASIN FLOW REVISITED: THE CONTRIBUTION OF LOCAL RECHARGE TO HIGH-DISCHARGE SPRINGS, DEATH VALLEY, CA

Springs in the Furnace Creek area of Death Valley exhibit high discharge rates and depleted d¹⁸O_VSMOW [~-13‰] and dD_VSMOW [~-102‰] values. Conventional wisdom suggests that modern depleted local recharge is unlikely, yet interbasin flow is difficult envisage due to lithology and the regional dip of bedrock in intervening ranges. High-flux springs at Furnace Creek respond to climate in terms of both discharge rate and isotopic composition. Hydrographs show a climate response and variations in time-series stable isotope data track one another, also suggesting a climate effect. Small, but measurable quantities of tritium (0.17 TU) are found at Nevares Spring in the Furnace area, suggesting a component of modern recharge. d¹³C_PDB values at Furnace Creek are also often depleted relative to Ash Meadows waters, considered by many to be the source of Furnace Creek waters, requiring the input of an unknown, but depleted CO₂ source. We consider this unlikely for flow through an aquifer of marine carbonate rocks. Estimates of discharge at Willow [Gold Basin, Black Mountains] and other mountain springs produce a discharge flux/km² of catchment that, by analogy, could support ~25% of the current discharge at Furnace Creek. Yet ¹⁴C data [model ages are between 5,500 and 11,000 yr.] suggest much of the water at Furnace Creek was recharged [locally or otherwise] during the most recent pluvial period when net infiltration was much higher and isotopically depleted. Chemical evolution models are also consistent with local recharge, and estimates of the thickness of alluvium in the Furnace Creek drainage provide adequate storage. Thus, discharge at Furnace Creek is consistent with local pluvial recharge, thus avoiding many of the conceptual difficulties related to interbasin flow.