As New Mexico considers the use of desalinated brackish water (less than 10,000 mg/L total dissolved solid) to diversify the public water supply, many questions must first be answered. Where are the brackish water resources? What data are available? What exactly is the water chemistry? How feasible is it to use brackish water for public supply?
Northeastern New Mexico is a geologically diverse area that includes the upper Pecos and Canadian river valleys, the eastern margin of the Sangre de Cristo Mountains, and the Raton and Las Vegas Basins, two north-trending assymetric structural basins formed during the late Cretaceous-Paleogene Laramide orogeny. The Raton and Las Vegas Basins are separated by igneous intrusive rocks of the Cimarron Arch, near Cimarron, NM. The gently-dipping eastern margins of these basins are defined by the Sierra Grande Arch and the Raton-Clayton volcanic field (Kelley, 2015; Broadhead, 2015).
The Jornada del Muerto is a north-south trending basin lying to the east of the main Rio Grande Rift system in Socorro, Sierra, and Doña Ana Counties, New Mexico. The basin is ~160 miles long, averages 20 miles in width, and deepens to the south. The basin is bounded to the east by Chupadera Mesa and the Oscura and San Andres Mountains, and to the west by the Caballo and Fra Cristobal Mountains and the San Pasqual Platform. The south end of the Jornada del Muerto Basin merges imperceptibly with the northeast end of the Mesilla Basin. Unlike the Rio Grande Rift basins to the west, the Jornada del Muerto is a broad syncline that plunges to the south-southeast, formed between east-dipping Paleozoic and Mesozoic strata along the Caballo-Fra Cristobal Uplift and west-dipping Paleozoic strata in the San Andres Mountains. The basin is thus not part of the late Tertiary Rio Grande Rift extensional system, and Santa Fe Group basin-fill sediments are generally less than 350 feet thick (Chapin, 1971; Lozinsky, 1987; Roybal, 1991). The Jornada Draw fault zone runs from north to south and roughly parallels the hinge of the syncline. This fault zone significantly affects the groundwater system in the central part of the basin (Newton et al., 2015).
The San Juan Basin is a large structural basin in northwestern New Mexico that formed during the late Cretaceous-Paleogene Laramide orogeny about 75 million years ago. The basin comprises all or parts of San Juan, McKinley, Rio Arriba, and Sandoval Counties, with a northern portion that extends into southwestern Colorado. The basin is bordered by basement-cored Laramide highlands, including the Nacimiento Uplift to the east, the Zuni Mountains to the south, the Defiance uplift to the west, and the San Juan Mountains in Colorado to the north. Laramide-age monoclines form the remaining boundaries of the basin (Kelley et al., 2014). The San Juan Basin region is a major producer of hydrocarbons, primarily natural gas, and extensive studies of the petroleum geology of the region have been conducted over the past several decades. Basin-wide hydrogeological assessments of the San Juan Basin were conducted by Stone et al. (1983), Craigg et al. (1989; 1990), Kaiser et al. (1994), Kernodle (1996), and Levings et al. (1996). Kelley et al. (2014) conducted a thorough hydrologic assessment of oil and gas resource development of the Mancos Shale in the San Juan Basin, which includes detailed discussions of groundwater salinity in the basin by depth and individual aquifers.
The Mimbres Basin is a structurally complex region in southwestern New Mexico, extending over an area of more than 5,000 square miles in parts of Grant, Luna, Doña Ana and Sierra Counties, and straddling the border with the Mexican Republic. The region has been subject to extensive geologic, geophysical, and hydrologic investigations over a period of almost a century, including Darton (1916), White (1931), Trauger (1972), Hanson et al. (1994), Hawley et al. (2000), and Kennedy et al. (2000). The Mimbres Basin is located at the intersection of the Basin and Range, southern Rio Grande Rift, and southern Transition Zone tectonic provinces (Mack, 2004). Dominant structural features in the region are northwest trending faults and folds associated with the Laramide orogeny, Tertiary magmatism and Quaternary tectonism (Finch et al., 2008). The greater Mimbres Basin is made up of an interconnected group of hydrologic sub-basins separated by fault-bounded uplifts, bounded to the east by the Goodsight Mountains, Sierra de las Uvas, and basalt flows and cinder cones of the West Potrillo Mountains. The Continental Divide defines the northern and western boundaries of the Mimbres Basin. The only major surface drainage in the basin is the Mimbres River (Hawley et al., 2000; Connell et al., 2005; Finch et al., 2008).
The New Mexico Bureau of Geology and Mineral Resources has a long history of conducting and supporting hydrogeologic investigations in the Estancia Basin of central New Mexico (selected references below). A compilation by R.E. Smith of the U.S. Geological Survey was published by the Bureau of Geology (then the NM Bureau of Mines and Mineral Resources) as part of its Groundwater Report series in the 1950s, and remains an important reference. The report by F.B. Titus, which encompasses the greater East Mountain area (including the northwestern side of Estancia Basin), was published as a Bureau of Geology Hydrologic Report and is another important source of information concerning groundwater availability and quality. During the 1980s, Bureau of Geology geologists conducted a variety of field studies that led to New Mexico’s proposal to have the federally funded superconducting super collider (SSC) constructed in this state. Although the SSC project was focused primarily on engineering geology, it resulted in the acquisition of data from shallow borings, trench studies, and geophysical investigations, and pulled together information from a variety of sources.
The southern Española Basin, in the Santa Fe region, was the focus of a multi-year, multi-disciplinary hydrogeologic study by the Aquifer Mapping Program, in collaboration with the New Mexico Office of the State Engineer (NMOSE), the U.S. Geological Survey (USGS) and other agencies. The purpose of this study was to improve the understanding of the water resources within the basin, which serves as the primary source of drinking water for most of the area’s population.
As part of the New Mexico Water Data Initiative, this 3-year project, cooperatively funded with the US Bureau of Reclamation's WaterSMART program, will improve water data accessiblity, efficiency of data collection and sharing, as well as developing tools to help address water management in the Pecos Valley region of southeastern New Mexico.
The NMBGMR has completed a new hydrogeology study of the Mimbres basin which characterizes water level changes in the region between 1980 and 2020. The geostatistical method of spatiotemporal kriging was used to create water level maps every five years; revealing trends of decreasing water tables in the Deming and Colmbus areas, and rising water tables in the areas west of Red Mountain, east of the Florida Mountains, and northeast of Columbus.
