PRELIMINARY WATER CHEMISTRY RESULTS FROM A HYDROGEOLOGIC STUDY IN THE SOUTHERN SACRAMENTO MOUNTAINS, NEW MEXICO

A regional hydrogeologic study is underway in the southern Sacramento Mountains seeking to evaluate groundwater residence time and identify flow paths and areas of groundwater recharge. A principal goal of this investigation is to characterize the interconnection of perched and regional aquifer systems in the Permian Yeso and San Andres Formations. As part of this study, local spring water samples have been collected for general chemistry, stable isotopes, and several relative age-dating analyses, including tritium, chlorofluorocarbons (CFCs), and carbon-14.

Geochemical analyses of spring waters show that 23 of the 28 springs sampled are calcium bicarbonate (Ca HCO₃) or calcium-magnesium bicarbonate (Ca-Mg HCO₃) type waters. Ion concentrations of strontium, chloride, sodium, and sulfate increase northward, consistent with a south-to-north trend of increasing abundance of evaporite facies within the Yeso Formation. Stable isotopic ratios correlate to elevation, more depleted from springs at higher elevations and more enriched at lower elevations. Preliminary results of this investigation suggest that the shallow groundwater system related to springs may be comprised of locally perched (or semi-perched) aquifers in the Yeso Formation, and that age of water is generally related to watershed-scale elevation and geographic variations. Shallow groundwater appears to be recharged at all elevations along the eastern slope of the Sacramento Mountains. Groundwater discharging from springs appears to be recharged in close proximity to the spring outlets, rather than from a regionally continuous aquifer system.