Abstract
In research using heat tracing technology to investigate the lateral hyporheic exchange in the shallow geological body of the riparian zone, the accurate estimation of temperature changes can provide a scientific basis for quantifying the process of lateral hyporheic exchange. To improve the accuracy of estimating temperature changes in the riparian zone, a hydrothermal coupling model considering parameter heterogeneity was established based on existing models of the relationship between thermal conductivity and saturation. The model was verified by temperature data from laboratory experiments, and the effect of the thermal conductivity prediction models was compared with that of the partial differential equation (PDE) modeling approach. The results show that the established hydrothermal coupling model can effectively characterize the temperature changes observed in a generalized laboratory model of the riparian zone, and the model simulation effects vary with the equivalent thermal conductivity models. In addition, several thermal conductivity empirical models are suggested for further application. The model parameter sensitivity analysis indicated that the hydraulic conductivityks, VG model parameters (αandβ) and heat capacity of soilCshave a relatively large effect on the temperature output of the model. The results of this study will provide reference for the selection of equivalent thermal conductivity model for simulating temperature variations in the riparian zone.
Highlights
In research using heat tracing technology to investigate the lateral hyporheic exchange in the shallow geological body of the riparian zone, the accurate estimation of temperature changes can provide a scientific basis for quantifying the process of lateral hyporheic exchange
To improve the accuracy of estimating temperature changes in the riparian zone, a hydrothermal coupling model considering parameter heterogeneity was established based on existing models of the relationship between thermal conductivity and saturation. e model was verified by temperature data from laboratory experiments, and the effect of the thermal conductivity prediction models was compared with that of the partial differential equation (PDE) modeling approach. e results show that the established hydrothermal coupling model can effectively characterize the temperature changes observed in a generalized laboratory model of the riparian zone, and the model simulation effects vary with the equivalent thermal conductivity models
We found that the large rootmean-squared error (RMSE) values for monitoring points T2, T4, T7, T9, and T10, which indicates that there is a large deviation between the simulated and observed values at these monitoring points. e value of R2 varied from − 1.17 to 1.00, and small R2 values were observed at monitoring points T20, T21, T23, T24, T25, T26, T27, and T28. ese monitoring points were all located near the upper surface of the sand tank, which implies that the consistency between the simulated temperature and the actual temperature is relatively poor when the established model is used to estimate the temperature of the shallow riparian zone
Summary
In research using heat tracing technology to investigate the lateral hyporheic exchange in the shallow geological body of the riparian zone, the accurate estimation of temperature changes can provide a scientific basis for quantifying the process of lateral hyporheic exchange. Fuchunjiang Reservoir (located in Zhejiang Province, China) as the field study area; they monitored the water level and temperature in the channel and riparian zone along the river transect to quantitatively describe the spatial heterogeneity and dynamic characteristics of the riparian lateral hyporheic exchange and explained the response relationship between the water stage and temperature in the riparian zone and the channel. In some software that simulates the heat transfer of a geological body, the equivalent thermal conductivity is usually considered a fixed value or is predicted according to the embedded empirical formula [17, 21, 22] In theory, this approach is not accurate. Some empirical formulas of the equivalent thermal conductivity have been embedded in the relevant simulation software, with the continuous development of thermal conductivity prediction models, more reasonable and accurate models may be ignored. erefore, we need to find a suitable modeling approach, so that different equivalent thermal conductivity models can be considered in hydrothermal coupling methods
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