THE TULAROSA BASIN AND HUECO BOLSON TRANSITION ZONE—A LINKED HYDROGEOLOGIC SYSTEM IN SOUTH-CENTRAL NEW MEXICO, USA

The Tularosa Basin (TB) and Hueco Bolson (HB) are major components of an interconnected series of deep structural basins in the Rio Grande rift tectonic province. This Neogene basin trend extends from central New Mexico, through far-western Texas, and into northeastern Chihuahua, Mexico, with the Rio Grande forming the International Boundary. Basins are primarily half-graben complexes, and the Santa Fe Group (SFG) comprises the bulk of the basin fill. Ancestral-Rio Grande facies in upper and middle SFG hydrostratigraphic units form the major aquifers, with higher flanking mountain and plateau uplands and the Rio Grande providing the only significant recharge sources in this arid to semiarid region. The central TB (White Sands and pluvial-Lake Otero) area is a typical bolson landform, with topographic closure and an undrained shallow groundwater-flow regime; and most of the HB is a topographically open semi-bolson, with subsurface drainage to the Rio Grande (Lower El Paso) Valley aquifer system. There is, however, a broad zone of topographic and hydrogeologic transition between the two basins that heretofore has not been well defined, particularly in terms of potential for interbasin groundwater flow. It is located 15-20 km north of the NM/TX Stateline (Lat. 32º N) and is here informally named the “Tularosa-Hueco transition zone” (THTZ).

Results of recent work by the NM Water Resources Research Institute-GIS section on digital characterization of the THTZ hydrogeologic framework are presented here. The area is of special interest because of 1) proximity to the El Paso/Ciudad Juárez metropolitan area (population about 2 million) and the Fort Bliss/White Sands Missile Range defense complex, and 2) the great potential for brackish-water production as well as groundwater storage and recovery operations. Hydrogeologic framework is defined in terms of 1) major lithofacies-assemblages grouped as informal SFG hydrostratigraphic units, and 2) basin-boundary and intra-basin structural controls. The GIS products (ESRI ArcGIS^® and Adobe Illustrator^®), including a map (1:100,000) of surficial features and three cross-sections (msl base), integrate surface and subsurface information that will be used in groundwater-flow and hydrochemical modeling.