| publications-861 |
PEER REVIEWED ARTICLE |
2015 |
Gabriel C. Rau , Mark O. Cuthbert , Andrew M. McCallum , Landon J. S. Halloran , Martin S. Andersen |
Assessing the accuracy of 1-D analytical heat tracing for estimating near-surface sediment thermal diffusivity and water flux under transient conditions |
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10.1002/2015jf003466 |
Simulation & Modeling |
Hydrological modeling |
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AbstractAmplitude decay and phase delay of oscillating temperature records measured at two vertical locations in nearâsurface sediments can be used to infer water fluxes, thermal diffusivity, and sediment scour/deposition. While methods that rely on the harmonicsâbased analytical heat transport solution assume a steady state water flux, many applications have reported transient fluxes but ignored the possible violation of this assumption in the method. Here we use natural heat tracing as an example to investigate the extent to which changes in the water flux, and associated temperature signal nonstationarity, can be separated from other influences. We systematically scrutinize the assumption of steady state flow in analytical heat tracing and test the capabilities of the method to detect the timing and magnitude of flux transients. A numerical model was used to synthesize the temperature response to different step and ramp changes in advective thermal velocity magnitude and direction for both a singleâfrequency and multifrequency temperature boundary. Timeâvariable temperature amplitude and phase information were extracted from the model output with different signalâprocessing methods. We show that a worstâcase transient flux induces a temperature nonstationarity, the duration of which is less than 1 cycle for realistic sediment thermal diffusivities between 0.02 and 0.13âm2/d. However, common signalâprocessing methods introduce erroneous temporal spreading of advective thermal velocities and significant anomalies in thermal diffusivities or sensor spacing, which is used as an analogue for streambed scour/deposition. The most timeâvariant spectral filter can introduce errors of up to 57% in velocity and 33% in thermal diffusivity values with artifacts spanning ±2âdays around the occurrence of rapid changes in flux. Further, our results show that analytical heat tracing is unable to accurately resolve highly timeâvariant fluxes and thermal diffusivities and does not allow for the inference of scour/depositional processes due to the limitations of signal processing in disentangling fluxârelated signal nonstationarities from those stemming from other sources. To prevent erroneous interpretations, hydrometric data should always be acquired in combination with temperature records. |
299091 |
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| publications-862 |
PEER REVIEWED ARTICLE |
2014 |
R. I. Acworth , Gabriel C. Rau , Andrew M. McCallum , Martin S. Andersen , Mark O. Cuthbert |
Understanding connected surface-water/groundwater systems using Fourier analysis of daily and sub-daily head fluctuations |
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10.1007/s10040-014-1182-5 |
Data Management & Analytics |
River Basins |
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No abstract available |
299091 |
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| publications-863 |
PEER REVIEWED ARTICLE |
2013 |
M. O. Cuthbert , R. Mackay |
Impacts of nonuniform flow on estimates of vertical streambed flux |
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10.1029/2011wr011587 |
Data Management & Analytics |
Precipitation & Ecological Systems |
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Key Points Nonâuniform flow fields cause errors in 1D heat tracer flux estimation methods Nonâvertical flow won't necessarily cause such errors Nonâuniform flow leads to differences in hydraulic and heat tracer estimates |
299091 |
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| publications-864 |
PEER REVIEWED ARTICLE |
2014 |
Stefan Krause , Fulvio Boano , Mark O. Cuthbert , Jan H. Fleckenstein , Jörg Lewandowski |
Understanding process dynamics at aquifer-surface water interfaces: An introduction to the special section on new modeling approaches and novel experimental technologies |
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10.1002/2013wr014755 |
Simulation & Modeling |
River Basins |
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No abstract available |
299091 |
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| publications-865 |
PEER REVIEWED ARTICLE |
2014 |
M. O. Cuthbert , G. C. Rau , M. S. Andersen , H. Roshan , H. Rutlidge , C. E. Marjo , M. Markowska , C. N. Jex , P. W. Graham , G. Mariethoz , R. I. A |
Evaporative cooling of speleothem drip water |
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10.1038/srep05162 |
Data Management & Analytics |
River Basins |
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AbstractThis study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as ÎŽ18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. |
299091 |
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| publications-866 |
PEER REVIEWED ARTICLE |
2014 |
Helen Rutlidge , Andy Baker , Christopher E. Marjo , Martin S. Andersen , Peter W. Graham , Mark O. Cuthbert , Gabriel C. Rau , Hamid Roshan , Monika |
Dripwater organic matter and trace element geochemistry in a semi-arid karst environment: Implications for speleothem paleoclimatology |
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10.1016/j.gca.2014.03.036 |
Simulation & Modeling |
River Basins |
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No abstract available |
299091 |
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| publications-867 |
PEER REVIEWED ARTICLE |
2014 |
Mark O. Cuthbert , Andy Baker , Catherine N. Jex , Peter W. Graham , Pauline C. Treble , Martin S. Andersen , R. Ian Acworth |
Drip water isotopes in semi-arid karst: Implications for speleothem paleoclimatology |
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10.1016/j.epsl.2014.03.034 |
Predictive Analytics |
River Basins |
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No abstract available |
299091 |
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| publications-868 |
PEER REVIEWED ARTICLE |
2015 |
Gabriel C. Rau , Mark O. Cuthbert , Martin S. Andersen , Andy Baker , Helen Rutlidge , Monika Markowska , Hamid Roshan , Christopher E. Marjo , Peter |
Controls on cave drip water temperature and implications for speleothem-based paleoclimate reconstructions |
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10.1016/j.quascirev.2015.03.026 |
Simulation & Modeling |
River Basins |
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No abstract available |
299091 |
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| publications-869 |
PEER REVIEWED ARTICLE |
2016 |
Monika Markowska , Andy Baker , Martin S. Andersen , Catherine N. Jex , Mark O. Cuthbert , Gabriel C. Rau , Peter W. Graham , Helen Rutlidge , Gregoir |
Semi-arid zone caves: Evaporation and hydrological controls on ÎŽ18O drip water composition and implications for speleothem paleoclimate reconstructions |
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10.1016/j.quascirev.2015.10.024 |
Data Management & Analytics |
River Basins |
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No abstract available |
299091 |
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| publications-870 |
PEER REVIEWED ARTICLE |
2013 |
M. O. Cuthbert , R. Mackay , J. R. Nimmo |
Linking soil moisture balance and source-responsive models to estimate diffuse and preferential components of groundwater recharge |
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10.5194/hess-17-1003-2013 |
Simulation & Modeling |
River Basins |
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Abstract. Results are presented of a detailed study into the vadose zone and shallow water table hydrodynamics of a field site in Shropshire, UK. A conceptual model is presented and tested using a range of numerical models, including a modified soil moisture balance model (SMBM) for estimating groundwater recharge in the presence of both diffuse and preferential flow components. Tensiometry reveals that the loamy sand topsoil wets up via preferential flow and subsequent redistribution of moisture into the soil matrix. Recharge does not occur until near-positive pressures are achieved at the top of the sandy glaciofluvial outwash material that underlies the topsoil, about 1 m above the water table. Once this occurs, very rapid water table rises follow. This threshold behaviour is attributed to the vertical discontinuity in preferential flow pathways due to seasonal ploughing of the topsoil and to a lower permeability plough/iron pan restricting matrix flow between the topsoil and the lower outwash deposits. Although the wetting process in the topsoil is complex, a SMBM is shown to be effective in predicting the initiation of preferential flow from the base of the topsoil into the lower outwash horizon. The rapidity of the response at the water table and a water table rise during the summer period while flow gradients in the unsaturated profile were upward suggest that preferential flow is also occurring within the outwash deposits below the topsoil. A variation of the source-responsive model proposed by Nimmo (2010) is shown to reproduce the observed water table dynamics well in the lower outwash horizon when linked to a SMBM that quantifies the potential recharge from the topsoil. The results reveal new insights into preferential flow processes in cultivated soils and provide a useful and practical approach to accounting for preferential flow in studies of groundwater recharge estimation. |
299091 |
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