Heat carried by ground water serves as a tracer to identify surface water infiltration, flow through fractures, and flow patterns in ground water basins. Temperature measurements can be analyzed for recharge and discharge rates, the effects of surface warming, interchange with surface water, hydraulic conductivity of streambed sediments, and basin-scale permeability. Temperature data are also used in formal solutions of the inverse problem to estimate ground water flow and hydraulic conductivity. The fundamentals of using heat as a ground water tracer were published in the 1960s, but recent work has significantly expanded the application to a variety of hydrogeological settings. In recent work, temperature is used to delineate flows in the hyporheic zone, estimate submarine ground water discharge and depth to the salt-water interface, and in parameter estimation with coupled ground water and heat-flow models. While short reviews of selected work on heat as a ground water tracer can be found in a number of research papers, there is no critical synthesis of the larger body of work found in the hydrogeological literature. The purpose of this review paper is to fill that void and to show that ground water temperature data and associated analytical tools are currently underused and have not yet realized their full potential.

http://www.geology.wisc.edu/~andy/GW_Heat%20as%20a%20Tracer.pdf

Heat as a ground water tracer.

[1] This work reviews the use of heat as a tracer of shallow groundwater movement and describes current temperature-based approaches for estimating streambed water exchanges. Four common hydrologic conditions in stream channels are graphically depicted with the expected underlying streambed thermal responses, and techniques are discussed for installing and monitoring temperature and stage equipment for a range of hydrological environments. These techniques are divided into direct-measurement techniques in streams and streambeds, groundwater techniques relying on traditional observation wells, and remote sensing and other large-scale advanced temperature-acquisition techniques. A review of relevant literature suggests researchers often graphically visualize temperature data to enhance conceptual models of heat and water flow in the near-stream environment and to determine site-specific approaches of data analysis. Common visualizations of stream and streambed temperature patterns include thermographs, temperature envelopes, and one-, two-, and three-dimensional temperature contour plots. Heat and water transport governing equations are presented for the case of transport in streambeds, followed by methods of streambed data analysis, including simple heat-pulse arrival time and heat-loss procedures, analytical and time series solutions, and heat and water transport simulation models. A series of applications of these methods are presented for a variety of stream settings ranging from arid to continental climates. Progressive successes to quantify both streambed fluxes and the spatial extent of streambeds indicate heat-tracing tools help define the streambed as a spatially distinct field (analogous to soil science), rather than simply the lower boundary in stream research or an amorphous zone beneath the stream channel.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2008WR006996

Heat as a tracer to determine streambed water exchanges

[1] Understanding how changes in the groundwater table affect surface water resources is of fundamental importance in quantitative hydrology. If the groundwater table below a stream is sufficiently deep, changes in the groundwater table position effectively do not alter the infiltration rate. This is referred to as a disconnected system. Previous authors noted that a low-conductivity layer below the surface water body is a necessary but not sufficient criterion for disconnection to occur. We develop a precise criterion that allows an assessment of whether surface water-groundwater systems can disconnect or not. We further demonstrate that a disconnected system can be conceptualized by a saturated groundwater mound and the development of a capillary zone above this mound. This conceptualization is used to determine the critical water table position at the point where full disconnection is reached. A comparison of this calculated critical water table position with a measurement of the water table depth in a borehole allows the assessment of the disconnection status. A sensitivity analysis of this critical water table showed that for a given aquifer thickness and river width, the depth to groundwater where the system disconnects is approximately proportional to the stream depth and the hydraulic conductivity of the streambed sediments and inversely proportional to the thickness of these sediments and the hydraulic conductivity of the aquifer. The conceptualization also allows the disconnection problem to be analyzed using both variably saturated and fully saturated groundwater models and provides guidance for numerical and analytical approaches.

/pdf/hydrogeologic-controls-on-disconnection-between-surface-kq5zw66w5s.pdf

Hydrogeologic controls on disconnection between surface water and groundwater

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/pdf/field-techniques-for-estimating-water-fluxes-between-surface-2qwgp14364.pdf

Field Techniques for Estimating Water Fluxes Between Surface Water and Ground Water

Heat as a tracer to quantify water flow in near-surface sediments

Well water temperatures are often collected simultaneously with water levels; however, temperature data are generally considered only as a water quality parameter and are not utilized as an environmental tracer. In this paper, water levels and seasonal temperatures are used to estimate hydraulic conductivities in a stream-aquifer system. To demonstrate this method, temperatures and water levels are analyzed from six observation wells along an example study site, the Russian River in Sonoma County, California. The range in seasonal ground water temperatures in these wells varied from <0.2 degrees C in two wells to approximately 8 degrees C in the other four wells from June to October 2000. The temperature probes in the six wells are located at depths between 3.5 and 7.1 m relative to the river channel. Hydraulic conductivities are estimated by matching simulated ground water temperatures to the observed ground water temperatures. An anisotropy of 5 (horizontal to vertical hydraulic conductivity) generally gives the best fit to the observed temperatures. Estimated conductivities vary over an order of magnitude in the six locations analyzed. In some locations, a change in the observed temperature profile occurred during the study, most likely due to deposition of fine-grained sediment and organic matter plugging the streambed. A reasonable fit to this change in the temperature profile is obtained by decreasing the hydraulic conductivity in the simulations. This study demonstrates that seasonal ground water temperatures monitored in observation wells provide an effective means of estimating hydraulic conductivities in alluvial aquifers.

Estimation of hydraulic conductivity in an alluvial system using temperatures.

[1] The presence of an unsaturated region beneath a streambed during groundwater pumping near streams can reduce the pumping capacity, change flow paths, and alter the types of biological transformations in the streambed sediments. A three-dimensional, multiphase flow model of two horizontal collector wells along the Russian River near Forestville, California, was developed to investigate the impact of varying the ratio of the aquifer to streambed permeability on (1) the formation of an unsaturated region beneath the stream, (2) the pumping capacity, (3) stream water fluxes through the streambed, and (4) stream water traveltimes to the collector wells. The aquifer to streambed permeability ratio at which the unsaturated region was initially observed ranged from 10 to 100. The size of the unsaturated region beneath the streambed increased as the aquifer to streambed permeability ratio increased. The simulations also indicated that for a particular aquifer permeability, decreasing the streambed permeability by only a factor of 2–3 from the permeability where desaturation initially occurred resulted in reducing the pumping capacity. In some cases, the stream water fluxes increased as the streambed permeability decreased. However, the stream water residence times increased and the fraction of stream water that reached that the wells decreased as the streambed permeability decreased, indicating that a higher streambed flux does not necessarily correlate to greater recharge of stream water around the wells.

/pdf/analysis-of-pumping-induced-unsaturated-regions-beneath-a-2vo62dmb35.pdf

D. Seymour

Papers

Estimation of hydraulic conductivity in an alluvial system using temperatures.

Analysis of pumping‐induced unsaturated regions beneath a perennial river

Pumping-Induced Unsaturated Regions Beneath a Perennial River

Use of Ground-water Temperature Patterns to Determine the Hydraulic Conductance of the Streambed Along the Middle Reaches of the Russian River, CA