Geologic influences on source-water mixing along a paleochannel in the Southern High Plains aquifer, New Mexico

• Autores: Jeff B. Langman, Andre S. Ellis
• Localización: Carbonates and Evaporites, ISSN 0891-2556, Vol. 25, Nº. 3, 2010, págs. 247-265
• Idioma: inglés
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• Resumen

  • Lithology and geologic structure of a paleochannel in the Southern High Plains aquifer were tested for possible influence on source water mixing that has been implicated in the alteration of water types within the Southern High Plains aquifer. Geochemical and physical data suggested changes to source-water mixing across short distances in the Southern High Plains aquifer as a result of location relative to a paleochannel center. Changes in saturated thickness because of changes in elevation of the aquifer base layer from paleochannel incision appear to be an important influence on water composition. The thicker saturated interval of the aquifer near the paleochannel center minimizes geochemical influences from smaller volume source waters such as agricultural recharge and cross-formational flow that differ in composition compared to the more dominant natural recharge from concentrated surface flow. The thinner saturated thicknesses of the paleochannel bank and paleohighland areas allow geochemical changes in source waters to be visible in mixed groundwater samples. Examination of the water columns through resistivity and temperature indicates stratified layers that corresponded to the three major source waters that were implied by the variable geochemical signal of the mixed groundwater samples. Changes in lithology along the paleochannel did not appear to influence the contribution of cross-formational flow as warmer, more conductive water was present across the site in the lowermost layer of the stratified aquifer. The influence of agricultural recharge appeared highly variable with strong differences in groundwater composition in the paleohighland area near large agricultural areas.