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Critical groundwater overdraft is one of the greatest water issues of our time. In California, decades of overdraft have resulted in the passage of the 2014 Sustainable Groundwater Management Act, which requires critically overdrafted groundwater basins to create groundwater sustainability plans for future groundwater management. Many managers are using managed aquifer recharge (MAR) in their overall sustainability portfolio, in an attempt to balance groundwater use. Soil maps have been used in the past to determine viability of managed aquifer recharge sites. However, soil maps do not account for the high permeability pathways that exist in the subsurface, which have the potential to provide high efficiency recharge to the water table. This paper emphasizes the utility of creating data dense fine resolution geostatistical models and generating many realizations of the subsurface, which can then be used for analysis to understand the variability in recharge potential for specific recharge sites. These geostatistical realizations were investigated using connectivity metrics to evaluate the spread of highly conductive pathways throughout the subsurface. Connectivity analyses of high conductivity pathways show confidence that the study site- three vineyards located in the floodplain between the Cosumnes River and Deer Creek in Elk Grove, CA - has the potential to provide efficient recharge to the water table. These connectivity analyses can be completed prior to running computationally expensive and time intensive groundwater models and can be used as a way to understand variance between realizations of these geostatistical models.

We present the results of two numerical models describing contributions of groundwater and heterogeneous heat sources to ice dynamics directly relevant to basal processes in East Antarctica. A two-phase, one-dimensional hydrothermal model demonstrates the importance of groundwater flow in vertical heat flux advection near the ice-bed interface. Typical, conservative vertical components of groundwater volume fluxes (from either topographical gradients or vertically channeled flow) on the order of ±1–10 mm/yr can alter vertical heat flux by ±50–500 mW/m2 given parameters typical for the interior of East Antarctica. This heat flux has the potential to produce considerable volumes of meltwater depending on basin geometry and geothermal heat production. A one-dimensional hydromechanical model demonstrates that groundwater is mainly recharged into saturated, partially poroelastic (i.e., vertical stress only; not coupled to a deformation equation) sedimentary aquifers during ice advance. During ice retreat, groundwater discharges into the ice-bed interface, which may contribute to water budgets on the order of 0.1–1 mm/yr. We also present an estimated map of potentially heterogeneous heat flow provinces using radiogenic heat production data from East Antarctica and southern Australia, calculated sedimentary basin depths, and radar-derived bed roughness. These are overlaid together to delineate the areas of greatest potential effect from these modeled processes on the ice sheet dynamics of the East Antarctic Ice Sheet.

We hypothesize that groundwater systems may be the main water transport mechanism over (distributed, inefficient) water sheets at large scales in the interiors of ice sheets where melt rates are very low. We compare melt rate magnitudes to potential groundwater volume fluxes and also calculate the theoretical transmissivity ranges of subglacial water sheet and groundwater flow systems. Theoretical groundwater systems are on par with or are more transmissive than water sheets for the upper half of the permeability spectrum. In addition, we develop a 2D cross-sectional subglacial flow path model that connects subglacial lakes near Dome C, East Antarctica. This model integrates subglacial water sheet flux and hypothetical groundwater flow forcing, better bridging two historically disparate modeling frameworks – subglacial hydrology and ice sheet hydrogeology. Our model results suggest that the water sheet thickness can be highly dependent on groundwater flux and that the water sheet transmissivity is within the total range of the modeled groundwater system transmissivity. We infer from these results that subglacial lake stability and basal radar reflections underneath the interior of East Antarctica may possibly be affected by groundwater flow.