New Mexico Geological Society Annual Spring Meeting — Abstracts

The southern Sacramento Mountains are an important source of recharge to the Lower Pecos Valley, Roswell Artesian Basin, and Salt Basin aquifers. Significant declines in water levels in wells, spring and stream flow have occurred in the past 15 years. In response, the Otero Soil and Water Conservation District and the NMBGMR initiated a multi-scale study of the regional hydrogeology to delineate areas and timing of ground water recharge, determine direction and rates of ground water movement, and understand interactions between different aquifers and the ground water and surface water systems in the mountains.

The Yeso Formation, which consists of layers of limestone, dolomite, sandstone, and siltstone, is the primary aquifer in the study area. Fractured limestones and dolomites are the main source of water for most springs and wells in the southern Sacramento Mountains. Recharge primarily occurs in the high mountains west of Mayhill where the Yeso Formation is exposed at the surface. Stable isotope data suggests that snow melt usually contributes significantly more to ground water recharge than summer precipitation. However, extreme summer precipitation events, such as those that occurred in 2006 and 2008 do recharge the ground water system, resulting in significant increases in water levels in wells and spring discharge.

The ground water system in the high mountains west of Mayhill is characterized by several fracture-controlled leaky perched aquifers that are interconnected by regional fracture networks and the surface water system. Snow melt in the high mountains recharges shallow perched aquifers that discharge at springs that feed streams and ponds where evaporation occurs. Water in ponds and streams may then recharge another shallow perched aquifer, which again may discharge at a spring at a lower elevation. This cycle may occur several times until the water is deep enough to be isolated from the surface water system. A deeper regional aquifer may exist in this area. East of Mayhill along the Pecos Slope, regional ground water flow is dominantly to the east towards the Roswell Artesian Basin. Some ground water also flows to the southeast towards the Salt Basin and to the west into the Tularosa Basin.