NEW MEXICO PROJECTS

• Major Projects
  • Middle Rio Grande Piezometers
  • Cross Sections on the Rio Grande
  • Rio Grande Compact and Pecos River Commission
  • Estimating evaportive losses: Jemez to Albq.
  • Rio Grande Travel Times
  • Urban Storm-Water Prog.
  • Flood Analysis
  • Mesilla Basin

• NAWQA Program
  • Rio Grande NAWQA

• Recently Completed Projects
  • Questa Mine, Red River Valley Basin
  • Travel time of Ground Water, Roswell Basin
  • Middle Rio Grande Basin
  • Monitoring and Pumpage in Albq
  • Contamination in Grants, NM
  • Flood Analysis, Navajo Nation
  • Chemical Modeling, Albuquerque
  • WIPP

• National Projects
  • USGS measures a century of floods
  • Rio Puerco Basin Studies

Travel Time of Ground Water Through the Artesian Aquifer of the Roswell Basin from Recharge on the Pecos Slope to Discharge near the Bitter Lakes Wildlife Refuge Area, Chaves County

Project Number: 8636-COS00
Project Chief: Rick Huff
Cooperator: New Mexico Bureau of Geology and Mineral Resources
Period of Project: April 1, 2005 to Sept 30, 2005

SUMMARY

Recharge to the artesian aquifer of the Roswell Basin occurs over a broad region east of the Sacramento Mountains known as the Pecos Slope where geologic units containing the artesian aquifer are exposed at land surface. Discharge from the artesian aquifer into sinkholes supports critical habitat for endangered species at the Bitter Lakes National Wildlife Refuge. The objective of the proposed work is to estimate the rate of movement of water from recharge areas, through the artesian aquifer, to discharge points within the Refuge. Travel times of ground water between recharge on the Pecos Slope to discharge from sinkholes and springs at the Refuge will be estimated based on analyses of anthropogenic tracers including 3H/3He, chlorofluorocarbons, and sulfur hexafluoride.

PROBLEM

Recharge to the artesian aquifer of the Roswell Basin occurs over a broad region east of the Sacramento Mountains known as the Pecos Slope where geologic units containing the artesian aquifer, including the San Andres Limestone, are exposed at land surface. Gypsum and mudstone deposits of the Seven Rivers Formation confine the artesian aquifer east of the recharge area. Ground water flows through the artesian aquifer east and south away from the recharge area to discharge into or near the Pecos River. Pathways of predevelopment discharge from the artesian aquifer included upward flow through fractures and solution channels in the overlying confining beds of the Seven Rivers Formation (Welder, 1983) sometimes discharging as springs as the base of sinkholes. Currently (2005), most discharge from the artesian aquifer is through ground-water withdrawal for irrigation. However, a fraction of the total recharge still discharges through predevelopment pathways. Natural discharge from the artesian aquifer through springs into sinkholes supports critical habitat for endangered species, including the Pecos Gambusia, the Pecos Bluntnose Shiner, the Interior Least Tern, the Pecos Puzzle Sunflower, the Bald Eagle, and the Peregrine Falcon, that reside at Bitter Lakes National Wildlife Refuge.

The potential effects of anthropogenic activities, including oil and gas exploration and residential development west of the Bitter Lakes National Wildlife Refuge, on water quality within the Refuge are of concern to Refuge management. The potential vulnerability of the Refuge to the results of these activities will depend, in part, on the rate of movement of water through the artesian aquifer to discharge sites in the Refuge area. Slower rates of movement potentially allow for more dispersion and degradation of contaminants prior to discharge of ground water at the Refuge (Wiedemeier and others, 1999).

Previous studies have yielded highly variable estimates of the rate at which ground water travels from recharge to discharge sites. Estimates of residence times of water in the artesian aquifer between recharge and discharge sites range from 40 to 100 years (Wolford and others, 1999) to as little as 5 years (Rabinowitz and others, 1977). Such widely differing estimates may reflect in part the extremely heterogeneous distribution of fracture-controlled hydraulic conductivity in the artesian aquifer.

OBJECTIVES AND SCOPE

The objective of the proposed work is to estimate the rate of movement of water from recharge areas, through the artesian aquifer, to discharge points within the Refuge. Sampling will be limited to the Bitter Lakes National Wildlife Refuge area.

APPROACH

Travel times of ground water between recharge on the Pecos Slope to discharge from sinkholes and springs at the Refuge will be estimated based on analyses of anthropogenic tracers including 3H/3He and chlorofluorocarbons as discussed by Ekwurzel and others (1994); and sulfur hexafluoride (SF6) as discussed by Busenberg and Plummer (2000). Water samples will be collected from springs near the base of sinkholes. Spring discharge areas will be identified by visual inspection and by measured spatial variations in water temperature along the base of sinkholes. A portable pump intake will be lowered to the base of a sinkhole near apparent areas of ground-water discharge. Approximately 5 to 10 water samples will be collected. Water samples will be handled to minimize exposure to the atmosphere. Analyses of SF6 and chlorofluorocarbons will be conducted by the USGS Chlorofluorocarbon Laboratory in Reston, Virginia. Analysis of 3H/3He will be conducted by the Miami Tritium Lab.

REFERENCES

Busenberg, E. and Plummer, L. N., 2000, Dating young groundwater with sulfur hexafluoride: natural and anthropogenic sources of sulfur hexafluoride: Water Resources Research, v. 36, p. 3011-3030.

Ekwurzel, B., Schlosser, P., Smethie, W.M., Jr., Plummer, L.N., Busenberg, E., Michel, R.L., Weppernig, R., and Stute, M., 1994, Dating of shallow groundwater: comparison o

Manga, M., 2001, Using springs to study groundwater flow and active geologic processes: Annual Review of Earth and Planetary Sciences, 2001, v. 29, p. 201-228.

Rabinowitz, D., Gross, G., & Holmes, C., 1977, Environmental tritium as a hydrometeorological tool in the Roswell Basin, New Mexico, I, II, III: Journal of Hydrology, v. 32, p. 3-46.

U.S. Geological Survey, 1989, Safety and environmental health handbook: U.S. Geological Survey Handbook 445-1-H, variously paged.

U.S. Geological Survey, 1997, Draft quality assurance plan for water-quality activities of the New Mexico District: unpublished document, U.S. Geological Survey, Water Resources Division, Albuquerque, New Mexico, 47 p.

Welder, G., 1983, Geohydrologic Framework of the Roswell Ground-Water Basin, Chaves and Eddy Counties, New Mexico: New Mexico State Engineer Technical Report 42, 28 p.

Wiedemeier, T., Rifai, H., Newell, C., & Wilson, J., 1999, Natural Attenuation of Fuels and Chlorinated Solvents in the Subsurface: Wiley & Sons, New York, 617 p.

Wolford, R., Romero, D., Silver, S., and Balleau, W. P., 1999, Source-Water Protection Zones for Bitter Lakes National Wildlife Refuge [unpublished]: Balleau Groundwater, Inc., 42 p.