ARE HIGH-DISCHARGE SPRINGS AT DEATH VALLEY, CA THE RESULT OF INTERBASIN FLOW OR LOCAL RECHARGE?

Springs in the Furnace Creek (Texas, Travertine, and Nevares) and Scotty’s Castle (Surprise, Staininger, and Grapevine) areas of Death Valley exhibit high discharge rates and depleted d¹⁸O_VSMOW (-13 to -14‰) and dD_VSMOW (-102 to -111‰) values. Isotopic depletion of this magnitude suggests that modern local recharge to these springs is unlikely, yet interbasin flow is difficult to envisage due to lithology and the stratigraphic and structural relationships of bedrock in intervening basins and ranges.

High-flux springs at Furnace Creek respond to climate in terms of discharge rate and isotopic composition. Hydrographs show a climate response and variations in time-series stable isotope data track one another. Small, but measurable quantities of tritium (<0.2 TU) are found at both areas, also suggesting a component of modern recharge. Thus, whatever the main source of water for these springs may be, there appears to be a subtle, but recent climatic influence. Estimates of flow at nearby mountain springs produce discharge rates/km² of catchment that, by analogy, could support from 25 to 100% of the flow at large Death Valley springs under the current climate. Yet, ¹⁴C model ages suggest valley-bottom springs contain a large component of older water, especially at Furnace Creek (5,500 to 14,500 yr.), suggesting that much of the water was recharged during the a pluvial period (Younger Dryas?) when net infiltration would have been much higher and isotopically depleted. ¹⁴C model ages are also of similar age, or younger, than many “up gradient” waters, rather than being older as would be expected for interbasin flow. Chemical evolution models are consistent with local recharge, and estimates of the thickness of alluvium and semi-consolidated Tertiary units in the Furnace Creek drainage seem to provide adequate storage. Thus, although Death Valley is the ultimate discharge location for regional groundwaters to seek, a careful study of these springs suggests that they are mainly supported by local pluvial recharge. This avoids the structural problems associated with interbasin flow and suggests that a more careful evaluation of the contributions of local recharge be conducted on a case-by-case basis.