AN EVOLVING CONCEPTUAL FRAMEWORK DESCRIBING THE VULNERABILITY OF DESERT SPRINGS: AN EXAMPLE FROM THE PANAMINT RANGE, DEATH VALLEY, USA (Invited Presentation)

Despite being located immediately within the Sierra Nevada rain shadow, the Panamint Range of Death Valley hosts over 180 springs which have ecological, cultural, and historical importance. The Panamint Range receives much less snow than the southern Sierra Nevada located to the west. In addition, what rain does occur, typically falls only at high elevations where the evaporative demand is less than the adjacent basins. Unfortunately, our understanding of the recharge processes, groundwater flowpaths, and geochemical processes affecting these springs is limited. Here we provide an assessment of the vulnerability of these springs to climate change based on an evolving conceptual framework developed for the larger southern Great Basin. We address the following questions: 1) where does the recharge come from that supports these quintessential desert springs, 2) which geologic units host the aquifers that support springflow, and 3) what are the residence times of these springs? Stable isotopic analyses of precipitation and springs in the study area indicate that snowmelt is the primary source of recharge for the springs. Most springs are supported by mountain-block recharge; however, three basin springs are supported by mountain-system and mountain-front recharge. Panamint Range springs are not connected to the regional flowpaths or proposed recharge areas that support springs in the Ash Meadows National Wildlife Refuge. Geochemical data and ⁸⁷Sr/⁸⁶Sr ratios indicate that mountain aquifers are hosted primarily in dolomitic units. Consequently, the observed geochemical trends can be explained by dedolomitization and the dissolution of gypsum. The mean residence times of the springs range from ~ 65 years to over 1800 years; eleven of the twenty-one springs that were measured have mean residence times less than 500 years. Seven springs have mean residence times greater than 1000 years. In general, the longest residence times are found at the lowest elevations and the shortest residence times are found at the highest elevations. An assessment based on our evolving conceptual model indicates that the springs of the Panamint Range are extremely vulnerable to the effects of climate change and may have limited buffering to these effects. In fact, four springs were not flowing during this study which were flowing 20 years ago. The continued desiccation of desert springs will severely impact aquatic BMI and microbiological communities and the riparian habitat that supports amphibian, reptile, and bird communities.