The potential effects of climate variability and change on water resources is a well recognized and urgent concern from the local to global scale ? one that has increasingly become a high priority for groundwater managers and policy makers. The strategic importance of groundwater to global water and food security will likely intensify under climate change as more frequent and intense climate extremes increase variability in precipitation, soil moisture, and surface-water availability. However, the reliable characterization and forecast of responses in groundwater to climate change is complicated by the complex, heterogeneous nature of global-scale atmospheric-ocean circulation systems that partially control interannual to multidecadal climate variability and associated periodic and reversible patterns in terrestrial hydrology. Natural climate variability on these time scales influences precipitation distribution in space and time, drought frequency and severity, snowmelt runoff, streamflow, and other hydrologic processes that can profoundly affect surface-water resources. Some studies have inferred teleconnections between global-scale atmospheric-ocean forcings and groundwater. Yet, few have established strong evidence of causal relation between interannual to multidecadal climate variability and recharge rates and mechanisms ? many important process-level questions remain.
This project will fill this critical knowledge gap by testing the hypothesis that transient recharge rates and corresponding groundwater-level fluctuations respond to the complex, heterogeneous interactions of local-scale vadose zone processes and properties and global-scale atmospheric-ocean circulation systems. In particular, our research will quantifying the frequency, intensity, and phase relation of nonstationary signals in long-term climatic and hydrologic time series data from 15 of the most important U.S. Principal Aquifers, and correlate the teleconnections to the 6 leading atmospheric-ocean circulation systems that affect U.S. climate variability. We will evaluate constructive and destructive interference of teleconnection signals in precipitation, and the filtering in the vadose zone that dampens those signals, eventually producing an altered recharge time series. We will use this insight to evaluate the relative importance of the atmospheric-ocean circulation systems on transient recharge rates under future climate change scenarios. The expected results will have a broad impact because time-varying rates of recharge will improve local to national-scale groundwater models and sustainability studies. The project creates rich and engaging teaching, training, and learning experience for undergraduate and graduate students from underrepresented groups in STEM. Additionally, we establish a model collaboration that enhances research and education between students and faculty from non-Ph.D. and Ph.D. granting institutions.
