New Mexico Geological Society Annual Spring Meeting — Abstracts

In November 2005, the New Mexico Bureau of Geology and Mineral Resources began a regional geology and hydrology study in the southern Sacramento Mountains. The goal of this study is to characterize ground water aquifers that supply water for domestic and agricultural needs in the Sacramento Mountains. Water level variations in approximately sixty domestic and municipal wells are measured bi-monthly, and eight wells have continuous data loggers installed. So far, 28 spring water samples have been collected for general chemistry, stable isotopes, and several relative age-dating analyses, including tritium, chlorofluorocarbons, and carbon-14.

Fractured limestone beds within the Yeso Formation are the primary aquifer for wells in the study area. Initial findings have shown that the abundant precipitation in July through October, 2006, increased hydraulic head in the aquifer, elevated water levels in most monitored wells, and induced greater discharge in springs and streams. Water levels in many wells began to rise as early as August, with an average increase in water level of 20 feet. Water levels in most wells rose in response to increased hydraulic head by October. Generally, wells along the crest of the mountain range and the western slope displayed the earliest and largest responses to precipitation.

In spring waters, concentrations of strontium, chloride, and sulfate increase northward, consistent with a north-south trend of increasing abundance of evaporite facies within the Yeso Formation. Lighter ²H:¹H and ¹⁸O:¹⁶O ratios from springs at higher elevations, and heavier ratios at lower elevations suggest that shallow groundwater is recharged at all elevations along the Sacramento Mountains eastern slope.