Comparison of 1-D analytical solutions and a numerical model for quantifying hyporheic exchange flux using the temperature tracer method

Abstract

Recently, the use of temperature tracer methods to investigate hyporheic exchange in rivers has attracted widespread attention. The quantification of the hyporheic exchange flux using temperature has been a topic of interest. Based on a summary and elaboration of the one-dimensional (1-D) analytical models for quantifying the hyporheic exchange flux based on the temperature tracer method, a hydrothermal coupling numerical model for the hyporheic zone considering the overall model of a river is further constructed. Combined with the water level and temperature time-series monitoring data collected from relevant rivers in the Walker Lake Basin in the United States, the effectiveness of the constructed numerical model in simulating the temperature and seepage patterns in the hyporheic zone is verified. Based on the verified hydrothermal coupling numerical model, the differences in the quantification of the vertical hyporheic exchange flux between different models are compared and analyzed. In addition, a sensitivity analysis based on the orthogonal test method is carried out to investigate the uncertainty of the 1-D analytical solution model. Finally, the advantages and disadvantages of the 1-D analytical model and the numerical model are discussed from the perspective of theoretical analysis. The results show that the constructed numerical model can be used to effectively characterize the heat transfer and fluid flow patterns in the hyporheic zone. When the result from the numerical model is not considered, the l-D analytical model based on the Hatch amplitude method is an ideal model for quantifying the vertical hyporheic exchange flux using temperature. The sensitivity analysis results reveal that the volumetric heat capacity of the soil (Cs) and the porosity (n) are relatively sensitive parameters for the Hatch solution.