Corinne I. Wong

Investigating groundwater flow between Edwards and Trinity aquifers in central Texas.

Understanding the nature of communication between aquifers can be challenging when using traditional physical and geochemical groundwater sampling approaches. This study uses two multiport wells completed within Edwards and Trinity aquifers in central Texas to determine the degree of groundwater inter-flow between adjacent aquifers. Potentiometric surfaces, hydraulic conductivities, and groundwater major ion concentrations and Sr isotope values were measured from multiple zones within three hydrostratigraphic units (Edwards and Upper and Middle Trinity aquifers). Physical and geochemical data from the multiport wells were combined with historical measurements of groundwater levels and geochemical compositions from the region to characterize groundwater flow and identify controls on the geochemical compositions of the Edwards and Trinity aquifers. Our results suggest that vertical groundwater flow between Edwards and Middle Trinity aquifers is likely limited by low permeability, evaporite-rich units within the Upper and Middle Trinity. Potentiometric surface levels in both aquifers vary with changes in wet vs. dry conditions, indicating that recharge to both aquifers occurs through distinct recharge areas. Geochemical compositions in the Edwards, Upper, and Middle Trinity aquifers are distinct and likely reflect groundwater interaction with different lithologies (e.g., carbonates, evaporites, and siliceous sediments) as opposed to mixing of groundwater between the aquifers. These results have implications for the management of these aquifers as they indicate that, under current conditions, pumping of either aquifer will likely not induce vertical cross-formational flow between the aquifers. Inter-flow between the Trinity and the Edwards aquifers, however, should be reevaluated as pumping patterns and hydrogeologic conditions change.

Evolution of moisture transport to the western U.S. during the last deglaciation

We investigate climate dynamics and teleconnections governing moisture transport to the western U.S. during past warm and cool intervals of the last deglaciation using paleoclimate simulations of the Bølling warm (~14ka) and Younger Dryas cool (~12 ka) events. Results suggest that the waning continental ice sheet weakened atmospheric pressure centers in the region leading to a progression from a more sinuous to more zonal Pacific winter storm track throughout the deglaciation. Furthermore, variations in meltwater flux to the Atlantic influenced the meridional temperature gradient over the Pacific and thereby modulated storm track intensity. Changing sinuosity of the storm track may be reflected in broad increases in modeled δOprecip and observed δ Ospeleothem values from the western U.S. over the last deglaciation, whereas abrupt δOspeleothem shifts are dynamically consistent with the response of storm track intensity to variations in meltwater flux to the Atlantic.