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Ogallala Geochemistry
CHEMICAL (Nativ, R. and Smith, D.A., 1987. Hydrogeology and geochemistry of the Ogallala aquifer, Southern High Plains. J. Hydrol., 91: 217-253.)


 * increase in TDS from 400 ppm in the northern half of the Southern High Plains to 3000 ppm in the southern half
 * northern and western part of Southern High Plains: Ca/cation-HCO3 facies
 * patterns show Ca > Mg > Na and HCO3 > SO4 > Cl
 * Mg-anion and Na-anion areas also common on the local scale
 * major hydrochemical facies are aligned from northwest to southeast following depositional systems
 * adjacent to Canadian River -- trends tend to follow local flow patterns

LITHOLOGICAL AND STRUCTURAL


 * three major alluvial fan systems with high percentages of sand and gravel
 * thickest, most permeable and porous
 * water has mostly mixed-cation-HCO3 and Ca-HCO3 and relatively depleted 18deltaO and deltaDeuterium
 * saturated thickness above 90 ft
 * higher sulfur 34 values
 * constant groundwater conditions because of flow through preferential pathways
 * between the fans, percentage of gravel and sand is much smaller and the aquifer is thinner
 * varied facies: mixed-cation-mixed-anion
 * delta-18O and delta-Deuterium relatively enriched relative to water in major fan axes
 * saturated thickness below 90 ft
 * higher salinity because of higher residence times -- heterogenous local flow conditions
 * Arsenic and nitrate contamination in areas with shallow water tables because clay cannot absorb the arsenic fast enough
 * extremely shallow water tables (<5ft) allow direct evaporation from the aquifer
 * saline lakes frequently located where water levels are between 5 and 50 ft below land surface
 * water near these lakes have unusual Na-SO4 and Na-Cl hydrochemical facies