User:Spacewanderer7/sandbox
Ogallala Geochemistry
[edit]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
- saline lakes frequently located where water levels are between 5 and 50 ft below land surface