Abstract
Within the US Southern High Plains, it is known that the Ogallala Aquifer (OA) has been over pumped since large-scale agriculture began making use of the water in the 1950s. One option to address the decline is to find new water sources. The last 10–15 years have seen an increase in drilling large capacity, deeper wells in the co-located Dockum Aquifer in the Texas Panhandle. This lower aquifer is separated from the OA by low hydraulic conductivity sediment and is thus generally considered independent from the OA. We examined the suitability of the Dockum to supplement OA water by comparing recent water chemistries where the aquifers coexist. We also examined historical information on well yield, well development, and water quality. We found that water quality is equivalent to the Ogallala in some places but in others it is saltier, softer, and more sodic. Use of PCA and hydrochemical facies revealed that even in this small area Dockum water quality is highly variable. We used USGS-PHREEQC to model water blending at ratios of 0–>100% Ogallala. We show that there is irrigation water quality risk no matter the blend, that risks differ according to location, and that the most frequent risks are salinity, sodicity, and nitrate. We conclude that growers can manage these risks if they use blending to choose the risks they feel most apt to mitigate.
Highlights
Looking at the various water quality parameters that move irrigation blends into slight or severe hazard classes, we examined how many blends of water in each region had no problems from any hazard type
We explored the differences in water quality between two co-located aquifers in the Texas Southern High Plains, the overlying water table Ogallala aquifer and the mostly confined sometimes brackish Dockum aquifer
We examined the differences with a view towards understanding spatial differences in water chemistry that could help evaluate their suitability in blending scenarios, most particular for irrigation of crops
Summary
Role of Water Scarcity and Declining Quality in the Ogallala Region. Observed annual groundwater level has declined well beyond natural recharge. These declines have been alarming in the southern portion of the aquifer region in Western Kansas, the Texas Panhandle, and the greater Llano Estacado. In these areas, the level of recharge is low relative to extracted groundwater [1,2,3,4]. The groundwater quality in the southern portion of the aquifer while generally good has seen noticeable decline, which appears to be linked to the declines in the quantity of water in the aquifer [5,6]
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