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Multi-tracer investigation of groundwater residence time in a karstic aquifer: Bitter Lakes National Wildlife Refuge, New Mexico, USA

Lewis Land, New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology; and the National Cave and Karst Research Institute; 1400 Commerce Dr., Carlsbad, NM, 88220, USA; 575-887-5508,

G.F. Huff, Huff HydroResources, Las Cruces, NM, 88001 [Current Address: Alberta Geological Survey, 402 Twin Atria Building, 4999 98 Avenue, Edmonton, AB, T6B 2X3, Canada; 780-427-2893,]

Bitter Lake & sinkholes aerial View    Photo © 2011: nckri


Several natural and anthropogenic tracers have been used to evaluate groundwater residence time within a karstic limestone aquifer in southeastern New Mexico, USA. Natural groundwater discharge occurs in the lower Pecos Valley from a region of karst springs, wetlands and sinkhole lakes at Bitter Lakes National Wildlife Refuge,on the northeast margin of the Roswell Artesian Basin. The springs and sinkholes are formed in gypsum bedrock that serves as a leaky confining unit for an artesian aquifer in the underlying San Andres limestone. Because wetlands on the Refuge provide habitat for threatened and endangered species, there is concern about the potential for contamination by anthropogenic activity in the aquifer recharge area. Estimates of the time required for groundwater to travel through the artesian aquifer vary widely because of uncertainties regarding karst conduit flow. A better understanding of groundwater residence time is required to make informed decisions about management of water resources and wildlife habitat at Bitter Lakes. Results indicate that the artesian aquifer contains a significant component of water recharged within the last 10 to 50 years, combined with pre-modern groundwater originating from deeper underlying aquifers, some of which may be indirectly sourced from the high Sacramento Mountains to the west.

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Key terms: karst, groundwater age, tracer tests, USA, Roswell Artesian Basin