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• A solution is derived for freshwater lenses with pumping and variable recharge. • The equation is verified with numerical methods and demonstrated through examples. • The approach is used to develop new vulnerability indices. Island freshwater lenses are often subjected to pumping to support the freshwater needs of isolated communities. Investigations of the lens extent commonly involve the application of analytical solutions, although the effects of pumping from circular island aquifers have not been assessed in previous analytical methodologies. In this study, a new analytical solution is derived based on Green's functions that accommodate freshwater inputs (recharge) and outputs (multiple wells) when obtaining the head distribution and sharp-interface lens shape. The solution is verified using a finite-element model for an illustrative pumping scenario. The solution is also differentiated with respect to pumping rates, recharge, and island radius to obtain vulnerability indices to characterize the lens sensitivity to changes in stresses. Finally, the analytical methodology is modified to examine the effects of non-uniform recharge. Python code incorporating the new solution is included to enable users to investigate a range of recharge and pumping scenarios. [ABSTRACT FROM AUTHOR]

Obtaining reliable estimates of vertical groundwater flows remains a challenge but is of critical importance to the management of groundwater resources. When large scale land clearing or groundwater extraction occurs, methods based on water table fluctuations or water chemistry are unreliable. As an alternative, a number of methods based on temperature-depth ( T-z ) profiles are available to provide vertical groundwater flow estimates from which recharge rates may be calculated. However, methods that invoke steady state assumptions have been shown to be inappropriate for sites that have experienced land surface warming. Analytical solutions that account for surface warming are available, but they typically include unrealistic or restrictive assumptions (e.g. no flow initial conditions or linear surface warming). Here, we use a new analytical solution and associated computer program ( FAST ) that provides flexible initial and boundary conditions to estimate fluxes using T-z profiles from the Willunga Super Science Site, a complex, but densely instrumented groundwater catchment in South Australia. T-z profiles from seven wells (ranging from high elevation to near sea level) were utilised, in addition to mean annual air temperatures at nearby weather stations to estimate boundary conditions, and thermal properties were estimated from down borehole geophysics. Temperature based flux estimates were 5 to 23 mm y − 1 , which are similar to those estimated using chloride mass balance. This study illustrates that T-z profiles can be studied to estimate recharge in environments where more commonly applied methods fail. [ABSTRACT FROM AUTHOR]

The modeling of freezing and thawing of water in porous media is an area of increasing interest. Examples include the modeling of permafrost degradation due to climate change, geotechnical applications in tunneling, and borehole heat exchanger performance in cold regions. Different code implementations have been developed and an interest has arisen in benchmarking different codes with analytical solutions, experiments, and numerical results. The name for this benchmark consortium is INTERFROST. Benchmark results are shown for a 1D analytical solution and two different 2D set-ups. All compared codes exhibit a similar behavior. [ABSTRACT FROM AUTHOR]

Highlights: [•] There has been little comparison of cold regions flow and heat transport models. [•] Analytical solutions make excellent benchmarks for inter-code comparison. [•] We present a solution that includes conduction, advection and phase change. [•] We test its accuracy via comparisons to the Neumann solution and a numerical model. [•] We report detailed simulation results to facilitate future benchmarking endeavors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Models for simulating heat and water processes in freezing soils are summarized. [•] The sources of existing variations in the Clapeyron equation are explained. [•] Various formulations for the soil freezing curve are reviewed. [•] Best practices to develop a frozen soil hydraulic conductivity model are detailed. [•] Several unresolved questions are highlighted and addressed. [ABSTRACT FROM AUTHOR]

Abstract: Traumatic internal carotid artery dissection may result from a direct blow to anterolateral aspect of the neck, or an extreme extension and rotation of the neck. Traumas involved are variable ranging from high speed motor vehicle accident to trivial traumas. The most frequent presentations of carotid artery dissection are stroke, Hörner syndrome, and paralysis of a cranial nerve. Time of ischemic signs onset is very variable too, diverging from immediate to several months delay. We report the case of a 60-year-old woman, who was assaulted by a young man. Immediately, she complained of headache and posterior cervical pain. Three months later she developed a left hemifacial paralysis. MRI and MRA showed a dissection of the left internal carotid artery. The causal relationship between the trauma and the carotid artery dissection as well as forensic issues are discussed. [Copyright &y& Elsevier]

While river water temperatures are a strong control on instream processes and aquatic ecosystems, monitoring networks for river water temperatures are often sparse. Despite recent advancements in water temperature modeling strategies, current models struggle to provide real-time and reach-specific predictions across broad spatial domains. We developed a physically-based water temperature model coupled to the National Water Model (NWM) to assess the potential for water temperature prediction to be incorporated into the NWM at the continental scale. Using model forcings and outputs from the NWM v2.1 retrospective, we evaluated the ability of four model configurations of increasing complexity to simulate hourly water temperatures in the forested headwaters of H.J. Andrews Experimental Forest, Oregon, USA during a six-week summer period. Our modeling framework, representing a first effort at pairing water temperature simulation with predictions from the NWM, suggests that the NWM can be leveraged to give insight into other water quality variables. • NWM-WT simulates hourly river water temperatures using National Water Model data. • Models of increasing complexity were calibrated and validated in a montane headwater catchment. • Select model configurations produced temperature predictions with RMSE values under 1 °C during the validation period. • Calibrated runs highlight the need to better constrain streambed and groundwater heat fluxes. [ABSTRACT FROM AUTHOR]

Numerical models of permafrost evolution in porous media typically rely upon a smooth continuous relation between pore ice saturation and sub-freezing temperature, rather than the abrupt phase change that occurs in pure media. Soil scientists have known for decades that this function, known as the soil freezing curve (SFC), is related to the soil water characteristic curve (SWCC) for unfrozen soils due to the analogous capillary and sorptive effects experienced during both soil freezing and drying. Herein we demonstrate that other factors beyond the SFC-SWCC relationship can influence the potential range over which pore water phase change occurs. In particular, we provide a theoretical extension for the functional form of the SFC based upon the presence of spatial heterogeneity in both soil thermal conductivity and the freezing point depression of water. We infer the functional form of the SFC from many abrupt-interface 1-D numerical simulations of heterogeneous systems with prescribed statistical distributions of water and soil properties. The proposed SFC paradigm extension has the appealing features that it (1) is determinable from measurable soil and water properties, (2) collapses into an abrupt phase transition for homogeneous media, (3) describes a wide range of heterogeneity within a single functional expression, and (4) replicates the observed hysteretic behavior of freeze-thaw cycles in soils. [ABSTRACT FROM AUTHOR]

Freshwater lenses underlying small ocean islands exhibit spatial variability and temporal fluctuations in volume, influencing ecologic management. For example, The Palmyra Atoll National Wildlife Refuge harbors one of the few surviving native stands of Pisonia grandis in the central Pacific Ocean, yet these trees face pressure from groundwater salinization, with little basic groundwater data to guide decision making. Adding to natural complexity, the geology of Palmyra was heavily altered by dredge and fill activities. Our study based at this atoll combines geophysical and hydrological field measurements from 2008 to 2019 with groundwater modeling to study the drivers of observed freshwater lens dynamics. Electromagnetic induction (EMI) field data were collected on the main atoll islands over repeat transects in 2008 following 'strong' La Niña conditions (wet) and in 2016 during 'very strong' El Niño conditions (dry). Shallow monitoring wells were installed adjacent to the geophysical transects in 2013 and screened within the fresh/saline groundwater transition zone. Temporal EMI and monitoring well data showed a strong contraction of the freshwater lens in response to El Niño conditions, and indicated a thicker lens toward the ocean side, an opposite spatial pattern to that observed for many other Pacific islands. On an outer islet where a stand of mature Pisonia trees exist, EMI surveys revealed only a thin (<3 m from land surface) layer of brackish groundwater during El Niño. Numerical groundwater simulations were performed for a range of permeability distributions and climate conditions at Palmyra. Results revealed that the observed atypical lens asymmetry is likely due to more efficient submarine groundwater discharge on the lagoon side as a result of lagoon dredging and filling with high-permeability material. Simulations also predict large decreases (40%) in freshwater lens volume during dry cycles and highlight threats to the Pisonia trees, yielding insight for atoll ecosystem management worldwide. Unlabelled Image • Limited fresh groundwater lenses support surface ecology on small atolls. • Human alteration of geology and natural climate cycles may impact lens dynamics. • Numerical modeling was used to explain unexpected geophysical field data. • Asymmetric lens weighting toward the ocean side driven by dredge and fill activities. • Small-island groundwater is highly sensitive to climate cycles, influencing surface ecology. [ABSTRACT FROM AUTHOR]

Streams strongly influenced by groundwater discharge may serve as “climate refugia” for sensitive species in regions of increasingly marginal thermal conditions. The main goal of this study is to develop paired air and stream water annual temperature signal analysis techniques to elucidate the relative groundwater contribution to stream water and the effective groundwater flowpath depth. Groundwater discharge to streams attenuates surface water temperature signals, and this attenuation can be diagnostic of groundwater gaining systems. Additionally, discharge from shallow groundwater flowpaths can theoretically transfer lagged annual temperature signals from aquifer to stream water. Here we explore this concept using multi-year temperature records from 120 stream sites located across 18 mountain watersheds of Shenandoah National Park, VA, USA and a coastal watershed in Massachusetts, USA. Both areas constitute important cold-water habitat for native brook trout ( Salvelinus fontinalis ). Observed annual temperature signals indicate a dominance of shallow groundwater discharge to streams in the National Park, in contrast to the coastal watershed that has strong, apparently deeper, groundwater influence. The average phase lag from air to stream signals in Shenandoah National Park is 11 d; however, extended lags of approximately 1 month were observed in a subset of streams. In contrast, the coastal stream has pronounced attenuation of annual temperature signals without notable phase lag. To better understand these observed differences in signal characteristics, analytical and numerical models are used to quantify mixing of the annual temperature signals of surface and groundwater. Simulations using a total heat budget numerical model indicate groundwater-induced annual temperature signal phase lags are likely to show greater downstream propagation than the related signal amplitude attenuation. The measurement of multi-seasonal paired air and water temperatures offers great promise toward understanding catchment processes and informing current cold-water habitat management at ecologically-relevant scales. [ABSTRACT FROM AUTHOR]