SCALED AND ECOLOGICAL PERSPECTIVES FOR GROUNDWATER SURFACE WATER INTERACTIONS IN TWO NORTH AMERICAN DESERTS (Invited Presentation)

Groundwater surface water interactions have intrigued ecologists and hydrologist for decades. Links between the two disciplines is frequently recognized and they have been integrated in North American deserts where they have focused on levels of groundwater use that conserve aquatic taxa in springs. This integration has focused on conserving single taxa, leaving broader ecological interactions largely unknown.

Desert springs are small, and most are isolated from other aquatic systems, where their size and use as primary sources for rural water have led to a belief that they are ecologically unimportant. Their importance to riparian systems, rare aquatic life, and wildlife have been increasingly recognized, and this has occurred while reliance on groundwater for municipal and urban economies is burgeoning and spring systems are increasingly threatened. Unfortunately, spring ecology is in its infancy and there is little information to respond to these challenges. Our work in Great Basin and Mojave Desert springs provides insight into their ecology, and links to groundwater hydrology.

We examined spatial variability in benthic macroinvertebrate (BMI) communities in spring systems as indicators of hydrogeology in a western Great Basin valley and in springs scattered throughout the Great Basin and Mojave Desert. Within the valley, communities varied in association with geology and groundwater geochemistry (primarily Ca:Na and other major ions). Patterns were also found across these deserts where BMI communities varied in context of aquifer provenance, landscape associations, and flow pathways, which also reflected geochemical characteristics of groundwater. These findings suggest an extraordinary linkage between aquatic ecology and groundwater geochemistry in these deserts. Further studies are needed to more fully understand spatial variability and the importance of scale to assessment. However, it is apparent that integrating these disciplines can provide important information to design monitoring and conservation programs, and to begin quantifying an interdisciplinary definition of sustainable levels of groundwater use.