Hydrological parameter estimations from a conservative tracer test with variable-density effects at the Boise Hydrogeophysical Research Site

• Published in: Water resources research Vol. 47; no. 12
• Main Authors: Dafflon, B., Barrash, W., Cardiff, M., Johnson, T. C.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-12-2011; John Wiley & Sons, Inc
• Subjects: Aquifers; AVAILABILITY; Boundary conditions; BROMIDES; Computer science; Datasets; DISTRIBUTION; Effective porosity; ENVIRONMENTAL SCIENCES; Experiments; Field tests; FORECASTING; Geophysics; Groundwater; Groundwater flow; HYDRAULIC CONDUCTIVITY; hydrogeophysics; Hydrology; Measurement techniques; Parameter estimation; POROSITY; SIMULATION; Solute transport; SOLUTES; tracer test; TRANSPORT; Transport processes
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2011WR010789

Reliable predictions of groundwater flow and solute transport require an estimation of the detailed distribution of the parameters (e.g., hydraulic conductivity, effective porosity) controlling these processes. However, such parameters are difficult to estimate because of the inaccessibility and complexity of the subsurface. In this regard, developments in parameter estimation techniques and investigations of field experiments are still challenging and necessary to improve our understanding and the prediction of hydrological processes. Here we analyze a conservative tracer test conducted at the Boise Hydrogeophysical Research Site in 2001 in a heterogeneous unconfined fluvial aquifer. Some relevant characteristics of this test include: variable‐density (sinking) effects because of the injection concentration of the bromide tracer, the relatively small size of the experiment, and the availability of various sources of geophysical and hydrological information. The information contained in this experiment is evaluated through several parameter estimation approaches, including a grid‐search‐based strategy, stochastic simulation of hydrological property distributions, and deterministic inversion using regularization and pilot‐point techniques. Doing this allows us to investigate hydraulic conductivity and effective porosity distributions and to compare the effects of assumptions from several methods and parameterizations. Our results provide new insights into the understanding of variable‐density transport processes and the hydrological relevance of incorporating various sources of information in parameter estimation approaches. Among others, the variable‐density effect and the effective porosity distribution, as well as their coupling with the hydraulic conductivity structure, are seen to be significant in the transport process. The results also show that assumed prior information can strongly influence the estimated distributions of hydrological properties.
Key Points
Choices about constraints influence the estimated hydrological parameters
Porosity distribution has a significant role in transport and sinking of solute
Hydrological relevance of incorporating various sources of data and information