27-1 Spatiotemporal Trends of Salinity and Chloride in the Roswell Artesian Basin, New Mexico

Session: From Data to Decision: Integrating Geophysics, Data Systems, and Modeling for Aquifer Characterization in Data-Sparse Regions (Posters)

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Abstract:

This study evaluates the spatiotemporal evolution of groundwater salinity and chloride concentrations in the Roswell Artesian Basin and examines their relationship to hydraulic gradients, pumping and hydrogeochemical processes. Depth-to-water (DTW), total dissolved solids (TDS), chloride concentrations, well depth, pumping records, and seasonal sampling data were analyzed to identify the mechanisms controlling chloride distribution and seasonal and long-term trends. Major ion, TDS, and DTW data were compiled from the New Mexico Bureau of Geology and Mineral Resources Data Integration Engine and supplemented with seasonal chloride measurements and annual pumping records from the Pecos Valley Artesian Conservancy District (PVACD) and the Roswell Basin Water Master Report of the Office of the State Engineer, respectively.

TDS and chloride concentrations exhibit significant spatial and temporal variability, with elevated concentrations generally follow regional hydraulic gradients and areas of intensive groundwater development. Seasonal analysis indicates that both spring and summer cumulative chloride concentrations have increased over time, with summer values showing greater variability. Although annual mean chloride concentrations do not show a simple linear relationship with total annual pumping, seasonal variations are related to periods of intensive groundwater withdrawal during summer. The decreases in chloride concentration observed in certain years likely reflect transient groundwater mixing processes.

Geochemical facies analysis indicates chloride-dominated water types across a wide range of depths. Elevated chloride concentrations in both shallow and deep wells, combined with relatively stable artesian heads support a conceptual model involving both lateral migration and localized vertical redistribution of saline groundwater. Seasonal pumping alters hydraulic gradients and flow condition and promotes temporal mixing, even in the absence of large water-level declines.

Overall, the results demonstrate that groundwater salinity dynamics in the Roswell Artesian Basin are controlled by the combined effects of confined aquifer hydraulic gradient, recharge variability, pumping, and hydrogeochemical process. These findings highlight the importance of integrating hydraulic gradient analysis with geochemical data to better understand salinity migration and spatiotemporal trends.

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