DEEP GROUNDWATER FLOW FROM THE SOUTHEASTERN COLORADO PLATEAU TO THE ALBUQUERQUE BASIN, NEW MEXICO

A numerical groundwater-flow model across the southeastern Colorado Plateau (CP) and the Albuquerque basin (AB) was developed to assess the effects of pumping from deep bedrock-aquifers on the AB and on Rio Grande surface flow. The transition between the AB and CP, referred to as the Rio Puerco fault zone and Laguna bench, remains poorly mapped. Six deep bedrock wells (out of 576 sites listed in “notices of intention” filed with the New Mexico Office of the State Engineer) have been completed so far. Eighty percent of the remaining notices of intention involve well sites within the transition zone, where the six wells have been completed more than 2,500 ft below ground surface.

To build a representative model of the CP–AB transition, we relied on existing USGS studies characterizing the San Andres–Glorieta aquifer, built cross sections, and categorized geochemical data for springs in order to develop a conceptual hydrogeological model of groundwater flow into the AB. Pre-Cenozoic aquifer units that crop out in the CP form the deep aquifer units in the AB. Cross-sections were built using stratigraphic sections, formation tops from oil and gas wells, and a revised structure-contour map of the base of the Dakota Sandstone. Along-strike and down-fault cross sections illustrating footwall-to-hanging-wall stratigraphic juxtapositions across major basin-margin faults show fault-bounding relay ramps that may have small but potentially transmissive windows where bedrock aquifer flow could be transferred to synrift deposits of the AB. Our conceptual model postulates that groundwater flow may be strongly controlled by geologic structures along the CP–AB transition. Groundwater flow may preferentially move along structural relay ramps and across west-stepping, east-down, basin-bounding normal faults into poorly consolidated deposits of the Santa Fe Group, which constitutes the regional aquifer system for the Albuquerque Basin.

Initial results from the numerical model suggest that groundwater flows from the Zuni Uplift to the AB, primarily along the Rio San Jose corridor, and abundant saline springs along the western flank of the Lucero Uplift may be structurally controlled. Model limitations include sparse groundwater elevation, surface-flow, and aquifer pumping-and-response data.