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DEVELOPING CRITERIA TO ASSESS THE RESISTANCE AND HYDROLOGIC STABILITY OF DESERT SPRINGS IN THE FACE OF A CHANGING CLIMATE
In arid regions, springs are important in many aspects of society due to the scarcity of surface water features. In the Great Basin of the United States, desert springs support the majority of regional biodiversity and are critical for supporting rare, threatened, and endangered organisms. Despite their importance, there are numerous threats to desert springs, with the most ubiquitous being climate change. In contrast to many studies examining potential metrics to describe the vulnerability of streams, wetlands and other surface water features to the effects of climate change, springs are often overlooked. Part of the knowledge gap stems from the complexity of springflow generation and the rarely field-tested connection between groundwater response time and groundwater residence time.
This dissertation tests, in a systematic way, different metrics that may help define criteria to evaluate whether a spring is likely to persist or desiccate with increasing regional hydrologic stress due to climate change. Field data was collected over a 4-year period from >80 springs across the topographically and geologically heterogeneous terrain of the southern Great Basin.
Throughout this dissertation, I use a variety of different tools (e.g., remote sensing, environmental tracers, geospatial analysis) to “attack” this complicated problem from different angles. I begin by examining factors indicative of hydrogeologic resistance to major drought. After finding a connection between groundwater residence time and hydrogeologic resistance, I examine other factors (e.g., geochemical, topographic, ecological, variability) that are related to groundwater residence time and also identify where these relationships fail.