Geochemical assessment of the degree of isolation of edge-of-aquifer groundwater along a fringe of the southern High Plains Aquifer, USA

Davidson, Gregg R.; Holt, Robert M.; Blainey, Joan B.

Geochemical assessment of the degree of isolation of edge-of-aquifer groundwater along a fringe of the southern High Plains Aquifer, USA | Évaluation géochimique du degré d’isolement des eaux souterraines du bord d’un aquifère le long de la frange de la partie sud de l’Aquifère des Hautes Plaines, États-Unis d’Amérique Evaluación geoquímica del grado de aislamiento del agua subterránea en el borde del acuífero a lo largo de una franja del sur del High Plains Aquifer, EEUU 沿美国高平原南部边缘含水层边缘地下水隔离程度的化学评价 Avaliação geoquímica do grau de isolamento das águas subterrâneas em borda de aquífero ao longo de uma franja do Aquífero das Altas Planícies austral, EUA

2019

Davidson, Gregg R. | Holt, Robert M. | Blainey, Joan B.

The edge of regional aquifers can be complex hydrodynamic systems with unique flow dynamics, water quality, and continuity relationships with the main aquifer system. A site near the southwestern margin of the High Plains Aquifer (USA) was investigated to characterize the local hydrogeology and its relationship with the regional aquifer system. Measurements of tritium, ion concentrations, oxygen and hydrogen isotopes, and hydraulic heads documented (1) a discontinuous saturated zone, (2) no inflow to the study area from the regional aquifer, (3) focused recharge beneath playas with limited local mixing between pockets of saturation, (4) outflow orthogonal to the regional aquifer flow direction, (5) localized multi-year reversals in flow direction following high precipitation events, and (6) a magnified influence of the paleo-erosional surface of the basement rock (Dockum Group) on groundwater isolation and flow direction. In isolated areas, groundwater can be trapped on decadal time scales by depressions in the Dockum, or by recharge events that periodically reverse groundwater gradients.

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