The agricultural economy of Union County in northeastern New Mexico is highly dependent on groundwater. Ongoing drought, large new groundwater appropriations both within the county and in adjacent parts of Texas, and large water level declines in wells have led to concern amongst county residents over groundwater supplies. This report documents the finding of a hydrogeology study to better understand the aquifers utilized in east-central Union County. The study began in 2010 and covers 650 square miles, from north of Clayton to south of Sedan, and east to the state line. The study was jointly sponsored by Northeastern Soil and Water Conservation District (NESWCD), the Aquifer Mapping Program of the New Mexico Bureau of Geology and Mineral Resources, and Healy Foundation.
The southern Taos Valley, located southwest of the town of Taos, has been experiencing high growth over the last few decades. In order to address growing water needs in this region, Peggy Johnson, Dr. Paul Bauer, and Brigitte Felix, completed a technical report summarizing the local geology and hydrogeology. Data gathered for this study include geologic maps, well records, new groundwater level measurements and water quality samples, which were compiled with historical data and records. This research describes the important hydrostratigraphic units and aquifers in the region along with geologic/structural controls on groundwater flow. Observations of groundwater flow directions, changes in groundwater levels, distinct water quality and groundwater ages reflect the complex network of faults in the study area and its effects on groundwater.
The Taos Plateau in northern Taos County is a high-elevation, basalt-capped plain that lies between the Rio Grande and the Tusas Mountains. The plateau overlaps the New Mexico-Colorado border and forms the west rim of the Rio Grande gorge. The hydrogeologic field investigation of the northern Taos Plateau, conducted between October 2007 and October 2009, is the first comprehensive assessment of groundwater conditions on the Taos Plateau and interactions between local aquifers and the Rio Grande. The investigative approach integrates new and existing geologic, geophysical, hydrologic, and geochemical data. This study has been undertaken in parallel with a major investigation of the springs in the Rio Grande gorge (Bauer et al., 2007). These studies advance understanding of the groundwater system in the northern Taos Plateau, and the interconnection of groundwater and surface water along the Rio Grande in northern Taos County.
The Albuquerque Basin is one of the largest (8,000 km2, 3,060 mi2) and deepest basins (4,407-6,592 m, 14,500-21,600 ft) of the Rio Grande rift. This basin contains the largest metropolitan area in New Mexico. Until 2008, this region relied entirely on groundwater for its water supply. This sole reliance on groundwater resulted from an earlier view that Albuquerque lay on top of the subterranean equivalent of a vast underground lake that would take centuries to exploit. Since the 1960s, the City of Albuquerque had little reason to be concerned about its water supply because wells drilled in the northeast and southeast heights yielded large quantities of potable groundwater. The view of plentiful groundwater was essentially unchallenged until the late 1980s, when water level declines near Coronado Center provoked exploration of the deeper aquifer. Results of the deep aquifer test wells led to reassessment of the regional aquifer and the Middle Rio Grande Basin Project of the late 1990s.
Groundwater is replenished by a process called recharge, where snowmelt and rain infiltrates through the soil and slowly moves through the subsurface to eventually reach an aquifer. Because groundwater recharge defines a limit for the availability of groundwater, estimating recharge for the state of New Mexico is necessary for effective water resource management.
The characterization of the Placitas area hydrology in the late-1990s was an important step for water resource planning and development. Local water levels were declining due to increased population and demand on groundwater supplies, with drought conditions in the mid-1990s. The Bureau of Geology initiated a study in 1997 to characterize the availability and quality of groundwater and surface water resources in the Placitas area. Findings were interpreted with detailed geologic maps and cross sections that supported a hydrogeologic conceptual model of groundwater flow and occurrence. The study was completed in 2002 and has been incorporated into the Placitas Area Development Plan by Sandoval County.
The goals of this study were to delineate areas of groundwater recharge, determine directions and rates of groundwater movement, and better understand the interactions between different aquifers and between the groundwater and surface water systems. Data collected from 2005 to 2009 include geologic mapping, frequent water level measurements in wells, single time and repeated well and spring sampling, precipitation measurement and sampling, fracture orientation measurements, and stream flow measurements.
Water for the city of Rio Rancho comes solely from groundwater held in the Santa Fe Group aquifer, which extends several thousands of feet below the surface. This aquifer is composed primarily of sand that was deposited over several million years as the Albuquerque basin dropped down along several major fault zones. What parts of this critical aquifer are most optimal for storing and transmitting this precious resource, and where are they located in the subsurface?
To answer these questions, the New Mexico Bureau of Geology and Mineral Resources studied permeability-related properties of Rio Rancho’s aquifer using both outcrops and well data. Within this aquifer, we mapped the depths and extents of hydrostratigraphic units and evaluated lateral changes in permeability within a given unit.
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 Española Basin is one of the northernmost basins of the Rio Grande Rift in New Mexico, and has been subject to extensive investigations in the past several decades (e.g., Kelley, 1978; Manley, 1979; Cordell, 1979; Golombek, 1983; Biehler et al., 1991; Johnson et al., 2008; Grauch et al., 2009). Although the Española Basin has the general form of a west-dipping half-graben, it exhibits a high level of structural complexity, consisting of a series of narrow, deep axial troughs in an otherwise shallow basin (Ferguson et al., 1995). The basin is ~50 miles long and 18 to 40 miles wide, and is linked to the east-dipping Santo Domingo Basin to the south at the La Bajada constriction. The basin is connected to the north with the east-dipping San Luis basin at the Embudo constriction. The Santa Fe Embayment occupies the southeast corner of the basin.
