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In permafrost regions, the thaw depth strongly controls shallow subsurface hydrologic processes that in turn dominate catchment runoff. In seasonally freezing soils, the maximum expected frost depth is an important geotechnical engineering design parameter. Thus, accurately calculating the depth of soil freezing or thawing is an important challenge in cold regions engineering and hydrology. The Stefan equation is a common approach for predicting the frost or thaw depth, but this equation assumes negligible soil heat capacity and thus exaggerates the rate of freezing or thawing. The Neumann equation, which accommodates sensible heat, is an alternative implicit equation for calculating freeze-thaw penetration. This study details the development of correction factors to improve the Stefan equation by accounting for the influence of the soil heat capacity and non-zero initial temperatures. The correction factors are first derived analytically via comparison to the Neumann solution, but the resultant equations are complex and implicit. Explicit equations are obtained by fitting polynomial functions to the analytical results. These simple correction factors are shown to significantly improve the performance of the Stefan equation for several hypothetical soil freezing and thawing scenarios. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Stream thermal regimes are controlled by the interactions of external and internal energy fluxes with the water in the channel. Solar radiation is typically the dominant driver of stream water temperature, but streambed heat fluxes can be important in forested headwater streams. Past studies have presented seemingly disparate formulae for quantifying streambed heat advection from upwelling groundwater. This note details the sources of the differences in these alternative formulations. The equations illustrate the difficulties of attempting to isolate the thermal influence of groundwater-surface water interactions and highlight future research opportunities. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Stream temperature is one of the most critical factors controlling aquatic ecosystem health. Practitioners and researchers from a range of fields, including biology, ecology, hydrology, engineering, and watershed management, are concerned with how climate and environmental changes are impacting stream thermal regimes. This primer provides an introduction to the various energy and water exchange processes that underpin stream temperature patterns from small headwater streams to large river systems. An overview of the various energy exchanges is provided, including (1) advection associated with hydrologic processes, and energy exchanges at (2) the stream–atmosphere interface and (3) stream–bed interface. The interaction and spatiotemporal variability of these energy exchange processes are discussed using a water and energy balance framework. A sound physical understanding and appreciation of the complex controls governing stream thermal regimes will help inform effective management strategies to sustain healthy aquatic ecosystems in a changing world. This article is categorized under:Science of Water > Science of WaterScience of Water > Hydrological ProcessesScience of Water > Water QualityWater and Life > Nature of Freshwater Ecosystems [ABSTRACT FROM AUTHOR]

Summary Streambed temperature and heat fluxes are important for aquatic habitats as well as in the development and improvement of water temperature models. In the present study, measured streambed temperatures at different depths were used as a tracer to predict the magnitude and direction of groundwater flow using an advection–conduction heat transport model. This analysis was carried out under different conditions, namely under natural surface water temperature conditions (i.e., as measured in the field), under steady-state conditions (e.g. under stream ice cover) and for conditions where the surface water temperatures followed a sinusoidal function. In Catamaran Brook, results from the advection–conduction numerical model showed good agreement between predicted and observed streambed temperatures with root-mean-square errors (RMSEs) ranging between 0.07 °C to 0.6 °C. A comparison of streambed fluxes showed that the heat flux by conduction was more important during the summer period for upwelling conditions (mean value 96 W m −2 at 25 °C), but was also present in winter (−20 W m −2 ). Variability in heat flux by conduction was also greater when the diel surface water temperature variability was high (e.g. range of 6 °C). The heat flux by advection varied between −120 and 145 W m −2 (for typical water temperatures and vertical flow conditions within Catamaran Brook, 0–25 °C and ±0.005 m h −1 ). Short-term heat exchange (diel) occurred within the thermally active depth, typically <0.7 m. The long-term annual streambed heat flux by conduction was also calculated and daily mean was generally less than ±11 W m −2 . Winter conditions provided a unique opportunity to analyse streambed heat fluxes under steady-state conditions when both conduction and advection fluxes were present. [ABSTRACT FROM AUTHOR]

Climate change is expected to increase regional and global air temperatures and significantly alter precipitation regimes. These projected changes in meteorological conditions will likely influence subsurface thermal regimes. Increases in groundwater and soil temperatures could impact groundwater quality, harm groundwater-sourced ecosystems, and contribute to the geotechnical failure of critical infrastructure. Furthermore, permafrost thaw induced by rising subsurface temperatures will likely alter surface and subsurface hydrology in high altitude and/or latitude regions and exacerbate the rate of anthropogenic climate change by releasing stored carbon into the atmosphere. This contribution discusses the theory and development of subsurface heat transport equations for cold and temperate regions. Analytical solutions to transient forms of the conduction equation and the conduction–advection equation with and without freezing are detailed. In addition, recently developed groundwater flow and heat transport models that can accommodate freezing and thawing processes are briefly summarized. These models can be applied to simulate climate change-induced permafrost degradation and dormant aquifer activation in cold regions. Several previous reviews have focused on the impact of climate change on subsurface hydraulic regimes and groundwater resources, but this is the first synthesis of studies considering the influence of future climate change on subsurface thermal regimes in cold and temperate regions. The current gaps in this body of knowledge are highlighted, and recommendations are made for improving future studies by linking atmospheric global climate models to subsurface heat transport models that consider heat advection via groundwater flow. [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]

Groundwater temperature is an important water quality parameter that affects species distributions in subsurface and surface environments. To investigate the response of subsurface temperature to atmospheric climate change, an analytical solution is derived for a one-dimensional, transient conduction-advection equation and verified with numerical methods using the finite element code SUTRA. The solution can be directly applied to forward model the impact of future climate change on subsurface temperature profiles or inversely applied to produce a surface temperature history from measured borehole profiles. The initial conditions are represented using superimposed linear and exponential functions, and the boundary condition is expressed as an exponential function. This solution expands on a classic solution in which the initial and boundary conditions were restricted to linear functions. The exponential functions allow more flexibility in matching climate model projections (boundary conditions) and measured temperature-depth profiles (initial conditions). For example, measured borehole temperature data from the Sendai Plain and Tokyo, Japan, were used to demonstrate the improved accuracy of the exponential function for replicating temperature-depth profiles. Also, the improved accuracy of the exponential boundary condition was demonstrated using air temperature anomaly data from the Intergovernmental Panel on Climate Change. These air temperature anomalies were then used to forward model the effect of surficial thermal perturbations in subsurface environments with significant groundwater flow. The simulation results indicate that recharge can accelerate shallow subsurface warming, whereas upward groundwater discharge can enhance deeper subsurface warming. Additionally, the simulation results demonstrate that future groundwater temperatures obtained from the proposed analytical solution can deviate significantly from those produced with the classic solution. Copyright © 2013 John Wiley & Sons, Ltd. [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]

Highlights: [•] Future projections for groundwater recharge are highly uncertain. [•] This uncertainty stems primarily from the variability in climate projections. [•] We simulated future recharge in a northern climate using seven climate scenarios. [•] The recharge was most sensitive to the choice of the post-processing method. [•] Suggestions for advances in future climate change-recharge projections are given. [ABSTRACT FROM AUTHOR]

Presents several correspondence on medical science in Great Britain. Failures of communication in the National Health Services; Assesses the accident service of general practitioners; Effects of two antihistamine drugs on actual driving performance.