REGIONAL WATER TABLE MAP OF THE SOUTHERN SACRAMENTO MOUNTAINS WATERSHED

We have prepared a map of the regional water table in the southern Sacramento Mountains based on measurements made in water wells in 2008, and elevations of flowing springs and gaining reaches of streams. The aquifer system in the southern Sacramentos is developed primarily within the Yeso Formation, a heterogeneous unit composed of siltstone, mudstone, gypsum and fractured limestone; thus geologic mapping of the southern Sacramentos by NMBGMR personnel has informed our hydrologic interpretation of the region.

Water-bearing zones are distributed throughout the Yeso section. The system is recharged near the crest of the Sacramentos where high mountain springs discharge from small, highly-localized perched aquifers. Streamflow derived from these springs re-enters the groundwater system along losing reaches and may “daylight” multiple times along the flowpath, feeding springs at lower elevations. As one follows the groundwater system downgradient from west to east, the perched aquifers begin to coalesce into a regional flow system that eventually merges with the Yeso-San Andres limestone aquifer in the Roswell Artesian Basin to the east. In most cases it is impossible to determine whether a measured water level corresponds to a perched aquifer or is part of the regional piezometric surface, and the distinction is probably irrelevant at the scale of observation of an entire watershed.

In the period from 2006 to 2007, water levels in the high Sacramentos began rising in response to unusually intense monsoonal rains in fall, 2006. Water levels continued to rise in the subsequent two years, but the center of greatest increase migrated progressively farther to the east, suggesting that the 2006 monsoon event was continuing to be felt as an eastward diffusion of pressure head through the aquifer system.