Depth to water and water quality in groundwater wells in the Ogallala aquifer within the North Plains Groundwater Conservation District, Texas Panhandle, 2019–20, and comparison to 2012–13 conditions

Craig A. Mobley; Patricia B. Ging

doi:10.3133/sir20225026

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Depth to water and water quality in groundwater wells in the Ogallala aquifer within the North Plains Groundwater Conservation District, Texas Panhandle, 2019–20, and comparison to 2012–13 conditions

Craig A. Mobley·Patricia B. Ging

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Abstract

The Ogallala aquifer is the primary source of water for agricultural and municipal purposes in the Texas Panhandle. Because most of the groundwater in the Texas Panhandle is withdrawn from the Ogallala aquifer, information on the quality of groundwater in the Ogallala aquifer in this part of Texas is useful for resource characterization. During 2012–13, the U.S. Geological Survey in cooperation with the North Plains Groundwater Conservation District (NPGCD), collected and analyzed water-quality samples from 30 groundwater monitoring wells in the Texas Panhandle. The results of the initial 2012–13 synoptic sampling were published in 2014 to help provide an initial characterization of the spatial and temporal variability of water quality in the NPGCD management area. This report documents the results of a followup synoptic sampling completed between March 2019 and July 2020 by the U.S. Geological Survey, in cooperation with the NPGCD, to further characterize the spatial and temporal characteristics of groundwater in the NPGCD management area; measurements of the depth to water, in feet below land surface, and water-quality samples were obtained from the same 30 monitoring wells that were sampled during 2012–13. The water-quality samples were analyzed for major ions, nutrients, trace elements, and selected organic compounds. Results from the 2019–20 synoptic sampling were compared to drinking-water standards and to the results from the 2012–13 synoptic sampling. Between the 2012–13 and 2019–20 sampling periods, the depth to water increased in 28 of the 30 wells, with a median difference of 18.17 feet. Results from major ion analyses indicate that most of the groundwater samples collected during 2019–20 were classified as magnesium-bicarbonate type, the same water type indicated for most samples during 2012–13. Dissolved-solids concentrations for the wells sampled during 2019–20 ranged from 260 to 774 milligrams per liter (mg/L) with a median dissolved-solids concentration of 316 mg/L, which was slightly higher than the median dissolved-solids concentration of 311 mg/L for the 2012–13 sampling period. Of the four nutrients analyzed, nitrate was the dominant nitrogen species, with a median nitrate concentration of 2.25 mg/L for the 2019–20 sampling period, which was a slight increase relative to the median nitrate concentration of 2.05 mg/L for the 2012–13 sampling period. Accounting for variability in analyses, median major ion concentrations and median concentrations for nutrient species were similar during the 2012–13 and 2019–20 sampling periods. None of the trace element concentrations exceeded any maximum contaminant level or secondary drinking-water standards. Median concentrations of trace elements from the 2012–13 sampling period were compared to those from the 2019–20 sampling period for constituents in cases where at least 50 percent of concentrations measured in the samples were detected at concentrations greater than the highest applicable laboratory reporting level, and variability in analyses was accounted for. Comparison results indicated that that median concentrations of two trace elements (lithium and uranium) increased, whereas median concentrations for two of the other trace elements measured (barium and molybdenum) decreased. Atrazine and deethylatrazine were the only organic compounds detected; both were detected in four of the six samples collected from different wells and analyzed for organic compounds. Concentrations of atrazine and deethylatrazine detections were all less than 0.05 micrograms per liter.

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Source-reported bounding extent: 35.36217605914681° to 36.474306755095235° latitude; -103.062744140625° to -99.986572265625° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Craig A. Mobley, Patricia B. Ging. 2022-04-29. Depth to water and water quality in groundwater wells in the Ogallala aquifer within the North Plains Groundwater Conservation District, Texas Panhandle, 2019–20, and comparison to 2012–13 conditions. https://doi.org/10.3133/sir20225026

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