Groundwater level response in U.S. Principal Aquifers to natural climate variability on interannual to multidecadal timescales
Monday, 15 December 2014
Natural climate variability on interannual to multidecadal timescales are important controls on precipitation, drought, evapotranspiration, streamflow, and groundwater recharge. Climate variability can also augment or diminish human stresses on water resources. Thus, understanding climate variability has particular relevance for groundwater management. Findings will be presented from a national scale study of groundwater level response to natural climate variability in principal aquifers (PAs) of the U.S., including the California Coastal Basin, Rio Grande, Coastal Lowlands, Mississippi Embayment, Floridan, and Glacial aquifer systems. We use the U.S. Geological Survey hydroclimatic analysis toolkit HydroClimATe to perform singular spectrum analysis and identify quasi-periodic signals in precipitation and groundwater time series that are coincident with the Arctic Oscillation (AO) (6–12 mo cycle), Pacific/North American oscillation (PNA) (<1–4 yr cycle), El Niño/Southern Oscillation (ENSO) (2–7 yr cycle), North Atlantic Oscillation (NAO) (3–6 yr cycle), Pacific Decadal Oscillation (PDO) (15–30 yr cycle), and Atlantic Multidecadal Oscillation (AMO) (50–70 yr cycle). Nearly all of the quasi-periodic signals in the precipitation and groundwater levels have a statistically significant lag correlation (95% confidence interval) with the AO, PNA, ENSO, NAO, PDO, and AMO indices. The largest amount of variance in precipitation and groundwater levels was attributed to the PDO, accounting for more than 90% of the variance in many PAs. The next largest amount of variance in precipitation and groundwater levels was attributed to ENSO, accounting for more than 50% of the variance in many PAs. The AMO was the least frequently detected signal in all time series but accounted for as much as 95% of the variance when detected. Thus, climate variability on interannual to multidecadal timescales has a statistically significant and measurable effect on the lagged responses of precipitation variability and, in turn, groundwater level fluctuations in PAs. Our findings have important implications for the availability and sustainability of groundwater, including management and planning decisions about the locations, cost effectiveness, and optimal time periods for conjunctive use strategies.