Old groundwater buffers the effects of a major drought in groundwater-dependent ecosystems of the eastern Sierra Nevada (CA)

Abstract

Global groundwater resources are stressed and the effects of climate change are projected to further disrupt recharge processes. Therefore, we must identify the buffers to climate change in hydrogeologic systems in order to understand which groundwater resources will be disproportionally affected by these changes. Here, we utilize a novel combination of remote sensing (e.g. Landsat) and groundwater residence time data ( ^3 H, ^36 Cl) to identify the factors controlling the hydrogeologic stability of aridland mountain-front springs in response to a major climate event, the 2011–2017 California drought. Desert springs within Owens Valley (CA) support unique ecosystems that are surrounded by lush, green vegetation sustained only by discharging groundwater and are not reliant on localized precipitation. Therefore, the health or ecological response of this vegetation is a direct reflection of the hydrogeologic stability of the mountain-block groundwater system since water is the limiting resource for riparian plant growth in arid regions. We compared spring water residence times to vegetation health metrics computed from Landsat imagery leading up to and during the drought interval. We observe that the vegetation surrounding springs discharging a high fraction of modern and bomb-pulse groundwater (100 years) showed little response thereby supporting the conceptual model where old groundwater, i.e. a distribution of deep and stable groundwater flowpaths, buffers short- to long-term climate perturbations and may provide hydrogeologic resistance to future effects from climate change.

Keywords

• hydrogeologic resistance
• groundwater-dependent ecosystems
• NDVI
• groundwater residence time
• Owens Valley