Desalinated brackish water has been discussed in New Mexico as a possible alternative supply for drinking water. The communities of Tularosa and Alamogordo continue to explore using brackish water as a municipal water supply, and plans are quite advanced toward production. The communities in this region are actively seeking information to insure protection of fresh water supplies while implementing the use of alternate source water sources - brackish groundwater.
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?
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 San Juan Basin, an important source of oil and gas located in northwestern New Mexico, has recently experienced renewed production from the Cretaceous Mancos Shale through the use of horizontal drilling and hydrofracturing. The Bureau of Land Management commissioned this study of the possible impacts of new exploration and development of this resource on the land surface and on the groundwater supply.
The Capitan Reef is a fossil limestone reef of middle Permian age that is dramatically exposed along the southeast flank of the Guadalupe Mountains in Eddy County, New Mexico, reaching its maximum elevation in west Texas, in Guadalupe Mountains National Park. In New Mexico, the reef serves as the host rock for the Big Room in Carlsbad Cavern. A few miles northeast of Carlsbad Caverns National Park, the reef dips into the subsurface and passes beneath the city of Carlsbad, where it forms a karstic aquifer that is the principal source of fresh water for that community (Land and Burger, 2008). The Capitan Reef continues in the subsurface east and south into Lea County, then south for ~150 miles to its southeasternmost outcrop in the Glass Mountains of west Texas.
The High Plains aquifer is one of the largest freshwater aquifers in the world, covering more than 170,000 square miles and extending across parts of eight states from South Dakota to the Texas Panhandle (Sophocleous, 2010). The first regional investigation of the High Plains was conducted by the U.S. Geological Survey at the beginning of the 20th century (Johnson, 1901). Since then, several regional studies have been conducted (e.g., Gutentag et al., 1984; Weeks et al., 1988), and a great many more localized investigations (e.g., Joeckel et al., 2014; Chaudhuri and Ale, 2014), reflecting the societal and economic importance of this very extensive aquifer system.
The Roswell Artesian Basin occupies over 4,000 square miles in the lower Pecos Valley in Chaves and northern Eddy Counties, and is one of the most intensively farmed regions in the state outside the Rio Grande Valley (Welder, 1983; Land and Newton, 2008). The eastern margin of the basin occurs just east of the Pecos River; the northern boundary is approximately defined by Macho Draw north of Roswell; and the southern end of the basin is located at the Seven Rivers Hills north of Carlsbad. The western margin of the basin is not as well-defined, but is usually located west of Roswell on the Pecos Slope near the Chaves-Lincoln County Line. The basin derives virtually all of its irrigation and drinking water from groundwater stored in a karstic artesian limestone aquifer contained within the Permian San Andres and Grayburg Formations, and from a shallow unconfined aquifer composed of Tertiary-Quaternary alluvial material deposited by the ancestral Pecos River. The Roswell Basin has been described by many workers as a world-class example of a rechargeable artesian aquifer system (e.g., Fiedler and Nye, 1933; Havenor, 1968).
The San Marcial and Engle Basins are axially-linked basins of the southern Rio Grande Rift system that connect the Socorro Basin with the Palomas Basin to the south (Connell et al., 2005). The Engle Basin is an east-tilted half graben containing ~2,000 feet of basin-fill material. Compared to other groundwater basins of the Rio Grande Rift, information specific to these two basins is limited. The compiled data contains only 32 data points for both basins. This very incomplete record indicates water in these basins is relatively fresh, with only four wells exceeding 1000 mg/l TDS.
The Palomas Basin is an east-tilted half graben ~35 miles long by 12 miles wide, bordered to the east by the Caballo Mountains and Red Hills, and to the west by the Black Range, Animas Hills, Salado Hills, and southern Sierra Cuchillo. The north end of the Palomas Basin is defined by the Mud Springs Mountains and several faults that intersect near Truth or Consequences, which separate the Palomas Basin from the Engle Basin to the north. The basin merges to the south with the eastern Mimbres Basin (Chapin, 1971). The Palomas Basin contains up to 6,500 feet of Tertiary alluvial fan and lacustrine sediments of the Santa Fe Group along its deep eastern margin, overlain by ~500 feet of alluvial fan and axial-fluvial sediments of the Plio-Pleistocene Palomas Formation (Mack, 2012).
