Browsing by Subject "Heat transport"
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Item Heat transport and tracing within the hyporheic zone of a pool-riffle-pool sequence(2010-05) Swanson, Travis Eric; Cardenas, Meinhard Bayani, 1977-; Bennett, Philip C.; Sharp, John M.Hyporheic water is thought to infiltrate at the head of a riffle which in turn is complemented by upwelling back to the stream at the tail of the riffle in a pool-riffle-pool (PRP) sequence. Heat tracing is a potentially useful method to characterize these hyporheic flow paths and quantify associated fluxes. Temperature was monitored within a PRP sequence for several days. Temperature in the hyporheic zone reflected the diel temperature change in the river but not uniformly. The observed thermal pattern exhibited deeper penetration of thermal oscillations below the head pool and shallower penetration below the tail pool. This pattern is consistent with the conceptual model of hyporheic exchange over a PRP sequence. One-dimensional analytical heat transport models were used at different points below the PRP sequence to estimate distributed vertical fluid fluxes. The calculated fluxes exhibit a trend that follows the expected distribution for a PRP sequence but modified for a losing stream. Deviation of both magnitude and distribution of fluxes from the conceptual ‘downwelling-to-upwelling’ model is partly due to the dominantly losing conditions at the study site but the trends are consistent with a losing stream undergoing hyporheic exchange. Violation of the assumptions in the analytical models most likely adds error to flux estimates. For this study, flux estimation methods using a temperature time series amplitude analysis more closely matched field measurements than phase methods.Item Investigation on heat transport in hyporheic zone using flume simulation and modeling(2011-08) Chan, Wai Sum, 1984-; Cardenas, Meinhard Bayani, 1977-; Wilson, Clark R.Recent research has shown that groundwater flow in hyporheic zone is critical in major hydrologic, ecological, and biogeochemical processes. Quantitative analyses from the literature show that there is a strong correlation between the diel cycles in pH, water temperature, and other parameters such as trace metal concentrations. There is, however, no controlled experimental data to illustrate how water temperature influences the trace metal concentrations and other parameters. The research study presented here illustrates the mechanism of heat is transported from stream water to groundwater in the hyporheic zone on different bed form. The work will serve as the foundation of future research in understanding the relationship of heat and trace metal concentrations in the sediments.Item Simulation of unsaturated flow and heat transport within playa soils(2012-12) Pavur, Robert; Rainwater, Ken; Zartman, Richard E.; Stovall, Jeff N.; Gitz, DennisThe primary objective in this research was to use the observed data and an appropriate unsaturated flow model to estimate the amount of water that can pass the root zone and eventually recharge the Ogallala aquifer for particular playas following specific inundation periods. The first step in approaching this challenge was to screen the field data collected by the playa instrument stations. This step was necessary to determine which parts of the data set provided complete description of the necessary field conditions. The second step was to select a software package that employed input parameters available in this research project either through collected field data or previous study results. Third, the available input parameters were provided to the model, and calibration of the model was performed. Most input parameters were determined with relative ease while others presented difficult challenges, which indicated future research topics. Finally, the modeled results were produced to provide estimates of potential recharge.Item Thermal dynamics of a riparian aquifer subject to flooding : lower Colorado River, Texas, USA(2016-08) Watson, Jeffery Allison; Cardenas, Meinhard Bayani, 1977; Neilson, Bethany T; Bennett, Philip CThe zone of mixing between rivers and the riparian aquifers adjacent to them, known as the hyporheic zone (HZ), is critical for water quality and water resource issues. Hyporheic mixing within the sediment provides a unique nexus of nutrients and environmental factors that promotes important biochemical reactions such as respiration, denitrification and anaerobic ammonia oxidation. Biochemical reaction rates are directly related to temperature. Moreover, temperature is a useful environmental tracer that may be used to infer groundwater flow paths in the HZ. In this study, I investigate coupled fluid flow and heat transport dynamics in riparian aquifers adjacent to the river channel during three flood events. I present 2D riparian aquifer temperature data from two sites along the Lower Colorado River (LCR). These data, along with river and groundwater table elevation data, allowed observation of riparian aquifer temperature responses to the flood pulses as they traveled downstream. At the downstream site (Webberville Park), pre-flood temperature penetration distance into the bank suggested advective heat transport from lateral exchange of river water into the riparian aquifer was occurring during relatively steady river flow conditions. While a small (20 cm) dam-controlled flood pulse had no observable influence on groundwater temperature regimes, larger floods (40 cm and >3 m) caused lateral movement of distinct heat plumes away from the river during flood stage, and retreated back toward the river after flood recession. We interpret these plumes as heat transport by advection caused by flood waters being forced into the adjacent riparian aquifer. These flood-induced temperature responses were controlled by the size of the flood, river water temperature during the flood, and local factors at the study sites, such as topography and local hydraulic gradients. For the two larger events, the thermal disturbance lasted days after flood waters receded, suggesting that large floods have long lasting impacts on the temperature regime of riparian aquifers beyond the time scale of the flood itself. These persistent flood-induced thermal disturbances likely have a significant impact on biochemical reaction rates and nutrient cycling in the river system.