UCSC GEOPATHS is an NSF-supported initiative to improve undergraduate success in the geosciences, driven by a desire to broaden academic engagement. One component of the program is a funded undergraduate summer program that provides authentic, professional experiences – across all employment sectors – to increase commitment in the geoscience pipeline. Many hydrologic basins rely on groundwater to supply domestic, municipal, and agricultural demand, but resources are increasingly stressed by rising demand, changes in land use, and a shifting climate. Consequences of groundwater overdraft include drying surface water systems, land subsidence, and seawater intrusion. Managed aquifer recharge (MAR) can help improve groundwater resources by increasing infiltration of excess surface water. We are part of a research team assessing hydrologic conditions during MAR on an active vineyard in Central California, through diversion of high flows from an adjacent river, a strategy known as “flood-MAR.” Our team collected soil samples from the upper 100 cm below ground surface at 24 locations across the 785-acre field site. We analyzed samples for soil texture at 10-cm spacing using a particle size analyzer based on laser light scattering. Preliminary analysis of fractions of sand, silt, and clay-sized particles indicate some lateral continuity from site to site. The northern part of the field area appears to be finer grained, on average, consistent with regional soil maps, but there is also considerable variability with depth. These data will be used to assess variations in expected infiltration rates by combining soil texture (to estimate infiltration capacity) and potential flood and saturation depths (to bracket vertical head gradients). Studies of this kind are helpful for assessing the efficacy of flood-MAR as a strategy to improve groundwater supplies and quality.

Insights from half a century investigating seafloor hydrothermal circulation on Earth can inform exploration on other Ocean Worlds. Early data/models for Earth provided useful predictions for flow at rift axes, but interpretations of the distribution of subseafloor circulation were revised significantly as data and simulations improved. Lessons learned for Earth systems elucidate how investigators might assess hydrothermal processes on other Ocean Worlds. Basin-scale morphology and heat flow indicate whether conduction explains the flux or cooling by seawater advection occurs. Detailed sonar mapping reveals areas where high flux is most likely. Seismicity patterns suggest different modes of circulation: East Pacific circulation is mapped via microseismicity within porous basaltic crust; Regional seismicity in the Atlantic highlights detachment-dominated rift segments, where faults channel circulation, sometimes within peridotite blocks that react with seawater. Exothermic serpentinization, also inferred for the lower ocean crust near subduction zones, should impart detectable temperature (T) signals. High-T/-flux circulation may be recognized with remote sensing (sonar, thermistors, chemical sensors, cameras) at the seafloor whereas low-T/-flux systems are difficult to identify. Modeling examines factors that influence hydrothermal circulation. Early models were simple single-pass cases; later data and more complex models show circulation includes multi-pass convection that can be 3D, unstable, and strongly guided by permeability patterns. Borehole observatories reveal heterogeneity in fluid chemistry and crustal microbiology. Interpreting Ocean World hydrothermal conditions will be challenging, but some fundamental inferences for Earth’s seafloor hydrothermal systems have proven robust. Early studies generated testable hypotheses, advanced instrumentation and simulations, and helped focus interdisciplinary discovery.