Development of a Plan of Study on the Hydrogeology and Groundwater Resources of the Salt Basin in New Mexico Completed

The recent discovery of natural gas within the Salt Basin of New Mexico has raised concerns over potential effects on groundwater quality associated with natural gas production. This discovery combined with an emerging interest in development of groundwater resources in the basin has emphasized the need to better understand the hydrogeology of the basin and the vulnerability of groundwater in storage to changes in groundwater quality.

The objective of the project is to formulate a plan of study to address hydrogeologic issues of concern in the Salt Basin of New Mexico. These issues include:

• Improving quantification of groundwater recharge, discharge and quality;
• Refining and increasing knowledge of the distribution and extent of high-permeability fractured zones within the principal aquifer;
• Refining estimates of total and recoverable groundwater in storage within the principal aquifer; and
• Assessing the potential vulnerability of groundwater resources to potentially associated changes in water quality during production of natural gas.

Benefits to the public include better estimates of groundwater resources in the basin and the potential effects on groundwater levels that may accompany groundwater withdrawal. Benefits to the State include an improved understanding of measures needed to protect this groundwater resource. Benefits to the U.S. Geological Survey include a better understanding of the hydrogeology of a potentially important groundwater resource in New Mexico.

PROBLEM

The Salt Basin is an extensional feature, typical of Basin and Range tectonics, which covers about 6,400 square miles of New Mexico and Texas. The New Mexico part of the basin covers about 2,400 square miles (Bjorklund, 1957). This project deals with the New Mexico part of the Salt Basin.

The principal aquifers in the New Mexico part of the Salt Basin are included in the San Andres Limestone, the Yeso Formation and the Abo Formation, all of Permian age. Groundwater largely flows through fractures in aquifers within the San Andres Limestone and the upper part of the Yeso Formation (Mayer, 1995). Groundwater levels indicate that regional flow is generally from northwest to southeast across the New Mexico part of the basin and suggests groundwater discharge by underground flow into the Texas part of the basin. 

Groundwater recharge to the New Mexico part of the Salt Basin is derived from precipitation in watersheds within elevated terrain located on the western flank of the basin.  The combined yield of these watersheds is about 35,078 acre-feet per year with about half of the combined yield coming from the watershed feeding the Sacramento River (Livingston Associates and John Shomaker and Associates, 2002). The presence of high-permeability fracture zones at or near land surface is thought to allow virtually all surface flow to infiltrate into the aquifer within the San Andres Limestone resulting in an estimated groundwater recharge of about 35,078 acre-feet per year (Livingston Associates and John Shomaker and Associates, 2002).  Discharge from the basin occurs as groundwater withdrawal, evapotranspiration, and underground flow into the Salt Basin of Texas. Ashworth (1995) cites a potential evaporation rate of about 80 inches per year from the basin floor of the northern part of the Salt Basin in Texas. Potential evaporation rates are likely similar for the basin-floor parts of the Salt Basin in New Mexico.  Groundwater withdrawals and associated return flows in 1995 were estimated to be 10,238 and 3,661 acre-feet, respectively (Livingston Associates and John Shomaker and Associates, 2002).

About 30 million acre-feet of groundwater with dissolved-solids concentrations less than 1,000 milligrams per liter and about 15.5 million acre-feet of groundwater with dissolved-solids concentrations between 1,000 and 3,000 milligrams per liter were estimated to be in storage in the principal aquifer as of 1995. Half of these volumes of groundwater are considered to be recoverable (Livingston Associates and John Shomaker and Associates, 2002). Problems associated with withdrawal of groundwater from fractured carbonate aquifers in the Salt Basin of Texas include substantial localized drawdown and the potential for encroachment of poorer-quality water (Gates and others, 1980; Angle, 2001; Ashworth, 1995).

The recent discovery of natural gas beneath Otero Mesa within the Salt Basin of New Mexico has raised concerns over potential effects on groundwater quality associated with natural gas production. The discovery of natural gas combined with an emerging interest in development of groundwater resources in the basin has emphasized the need to better understand the hydrogeology of the basin and the vulnerability of groundwater in storage to changes in water quality.

OBJECTIVES AND SCOPE

The objective of the proposed work is to formulate a plan of study to address hydrogeologic issues of concern in the Salt Basin of New Mexico. These issues include:

• Improving quantification of groundwater recharge; discharge, and quality;
• Refining and increasing knowledge of the distribution and extent of high-permeability fractured zones within the principal aquifer;
• Refining estimates of total and recoverable groundwater in storage within the principal aquifer; and
• Assessing the potential vulnerability of groundwater resources to potentially associated changes in water quality during production of natural gas.

The issues proposed for investigation in the plan of study may be changed or refined based on information gathered during formulation of the plan. The plan of study will call for work in the Salt Basin of New Mexico and, if needed, in the adjacent parts of the Salt Basin in Texas.

The plan of study will be developed in consultation with Sandia National Laboratories and the New Mexico Interstate Stream Commission. Data currently held by the above entities are needed in order to prepare a reasonable and beneficial plan of study. 

RELEVANCE AND BENEFITS

Protection and effective development of about 45 million acre-feet of usable water is inherently relevant on local and state levels.  Benefits to the public include better estimates of groundwater resources in the basin and the potential effects on groundwater levels that may accompany groundwater withdrawal.  Benefits to the State include an improved understanding of measures needed to protect this groundwater resource.  Benefits to the U.S. Geological Survey include a better understanding of the hydrogeology of a potentially important groundwater resource in New Mexico.  The proposed work will address the mission of the U.S. Geological Survey Cooperative Water Program – to provide reliable, impartial, and timely information to understand the Nation’s water resources and enable decision makers to wisely manage those resources.

APPROACH

The plan of study will be developed in consultation with Sandia National Laboratories and the New Mexico Interstate Stream Commission. Data currently held by the above entities are needed in order to prepare a reasonable and beneficial plan of study.  Specific tasks to be completed in preparation of the plan of study include:

• Reviewing available literature pertaining to the hydrogeology of the Salt Basin and inspecting data currently held by Sandia National Laboratories and the New Mexico Interstate Stream Commission,
• Attending meetings required to discuss development of the plan of study with participating parties,
• Visiting field sites of perspective new data collection, and
• Preparing and reviewing the plan of study.

REFERENCES

Angle, E.S., 2001, Hydrology of the Salt Basin, in Mace, R.E., Mullican, III, R.F., and Angle, E.S., (eds.), Aquifers of West Texas: Texas Water Development Board Groundwater Report 356, p. 232-247.

Ashworth, J.B., 1995, Ground water resources of the Bone Spring-Victorio Peak aquifer in the Dell Valley area, Texas: Texas Water Development Board Report 344, 42 p.

Bjorklund, L.J., 1957, Reconnaissance of groundwater conditions in the Crow Flats area, Otero County: New Mexico State Engineer Technical Report 8, 26 p.

Gates, J.S., White, D.E., Stanley, W.D. and Ackerman, H.D., 1980, Availability of Fresh and slightly saline ground water in the basins of westernmost Texas: Texas Department of Water Resources Report 256, 108 p.

Livingston Associates and John Shomaker and Associates, 2002, Tularosa Basin and Salt Basin regional water plan 2000-2040: South Central Mountain R, D, and C Council, Carizozo, New Mexico, v. 1, variously paged.

Mayer, J.R., 1995, The Role of Fractures in Regional Groundwater Flow: Field Evidence and Model Results from the Basin-and-Range of Texas and New Mexico: Ph.D. Dissertation, University of Texas – Austin, Austin, Texas, 218 p.