High-resolution mapping of the freshwater–brine interface using deterministic and Bayesian inversion of airborne electromagnetic data at Paradox Valley, USA

Ball, Lyndsay B.; Bedrosian, Paul A.; Minsley, Burke J.

High-resolution mapping of the freshwater–brine interface using deterministic and Bayesian inversion of airborne electromagnetic data at Paradox Valley, USA | Cartographie haute résolution de l’interface eau douce–eau saumâtre à partir de l’inversion déterministe et Bayésienne de données électromagnétiques aéroportées de la Vallée du Paradoxe, Etats-Unis d’Amérique Mapeo de alta resolución de la interfaz agua dulce–salmuera usando inversión determinística y bayesiana de datos electromagnéticos aéreos en Paradox Valley, EEUU 美国Paradox山谷利用航空电磁数据的确定性和贝叶斯反演对淡水–卤水界面进行高分辨率制图 Mapeamento de alta resolução da interface água–salmoura usando inversão determinística e bayesiana de dados eletromagnéticos aéreos em Paradox Valley, EUA

2020

Ball, Lyndsay B. | Bedrosian, Paul A. | Minsley, Burke J.

Salt loads in the Colorado River Basin are a primary water quality concern. Natural groundwater brine discharge to the Dolores River where it passes through the collapsed salt anticline of the Paradox Valley in western Colorado (USA) is a significant source of salt to the Colorado River. An airborne electromagnetic survey of Paradox Valley has provided insights into the three-dimensional distribution of brine in the surficial aquifer. A combination of stochastic and deterministic resistivity inversions was used to interpret the top of the freshwater–brine interface and to qualitatively describe the vertical salinity gradients across the interface. Low-resistivity regions indicative of brine occur near the land surface where brine discharges to the Dolores River and increase in depth several kilometers up-gradient along the axis of the valley. The most conductive parts of the brine plume are found in the areas below and adjacent to the river, suggesting that the brine becomes shallower and more concentrated as it reaches its natural discharge location. A significant freshwater lens overlying the brine west of the Dolores River is spatially correlated to the intermittent West Paradox Creek and agricultural irrigation. Below this lens, the transition from freshwater to brine appears to occur abruptly over a few meters and correlates to available well information. However, away from these regions and particularly with distance from the river, the freshwater–brine interface appears to be more diffuse.

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