Browsing by Subject "Edwards aquifer"
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Item Edwards Aquifer and Desalination(The Center for Global Energy, International Arbitration, and Environmental Law, 2013-09-16) Brown, JeremyItem Hydrogeologic atlas of the Hill Country Trinity Aquifer, Blanco, Hays and Travis Counties, central Texas(2010-10) Hays Trinity Groundwater Conservation District; Barton Springs/Edwards Aquifer Water Conservation District; Blanco-Pedernales Groundwater Conservation DistrictItem Hydrogeological analysis of groundwater chemistry and sulfate distribution, Blanco and Hays Counties, Texas(2010-05) Andring, Megan J., 1984-; Sharp, John Malcolm, 1944-; Bennett, Philip C.; Helper, Mark A.High concentrations of sulfate in groundwater, up to ten times the amount recommended by the EPA, in Blanco and Hays Counties, Texas, are of concern as groundwater pumping and population increase. The goals of this study are to characterize the chemistry of groundwaters in Blanco and Hays Counties within the context of Texas Groundwater Management Area-9 and to determine chemically and hydrogeologically the explanation for the spatial distribution of sulfate between the Pedernales River, the Blanco River, and Onion Creek. Insights gained by examining sulfate distribution in Blanco and Hays Counties can be applied to the other counties on the Edwards-Trinity Plateau with similarly high concentrations of sulfate in groundwater. Hydrochemical data from the Cretaceous Edwards and Trinity Groups and water level measurements were used to analyze groundwater chemistry and flow. PHREEQC was used to examine whether phase changes in aquifer minerals could explain the observed geochemical patterns. COMSOL was used to develop a simplified groundwater flow model for a cross-sectional area between the Pedernales River and Onion Creek in Hays County. Water levels indicate that groundwater generally flows southeast in the study area and most streams are gaining. The groundwater flow model indicates a zone of slow-moving groundwater beneath the topographic high between the Pedernales River, the Blanco River, and Onion Creek. Chemical analyses of well data show the presence of four groundwater chemical endmembers in Groundwater Management Area-9; a Ca-Mg-HCO3 fresh endmember, a Ca-Mg-SO4 endmember, a Ca-Mg-SO4-Na-Cl endmember, and a Na-Cl endmember. High sulfate waters generally come from the Upper and Middle Trinity aquifers while fresher waters are from the Edwards aquifer. Physical and chemical analyses indicate that the zone of high sulfate in Blanco and Hays Counties may be the result of gypsum dissolution and dedolomitization in the Upper and Middle Trinity aquifers combined with low rates of groundwater flow beneath the topographic high. Groundwater flow analyses are consistent with those for the Groundwater Availability Models published for the region. Chemical analyses, specifically SO4 distributions and Ca/Mg ratios, are consistent with those found by Nance(2010) on the Edwards Plateau, farther west of the study area.Item Identification and Quantification of Municipal Water Sources Contributing to Urban Streamflow in the Austin, Texas Area(Graduate School of The University of Texas at Austin, 2013-05) Snatic, Jonathan W.Previous studies have shown that municipal water can provide a substantial surface water and groundwater recharge source for the Edwards aquifer in central Texas. Knowledge of how water sources to urban watersheds change with urbanization is essential for sustainable water resource management. The range for 87Sr/86Sr values for Austin municipal water (0.7086–0.7094) is distinct from that of naturally occurring phreatic groundwater (0.7076-0.7079) and stream discharge in many rural watersheds (0.7077– 0.7084). Many streams in urbanized Austin watersheds have elevated 87Sr/86Sr values (0.7085–0.7088) relative to these rural streams. These differences demonstrate the potential for Sr isotopes to serve as a tracer of municipal water inputs to urban streamflow. A few urban streams and springs, however, have 87Sr/86Sr values higher than those of municipal water. Soil is the likely source of these elevated values. Spatial variability in the distribution of high 87Sr/86Sr soil and temporal variability in soil-exchangeable Sr contributions to groundwater may result in naturally high streamflow 87Sr/86Sr values, making the identification and quantification of municipal water as a streamflow source using Sr isotopes unreliable in some instances. Temporal variability in climatic conditions and resulting changes in effective moisture can result in distinct natural groundwater 87Sr/86Sr and Mg/Ca ratio variations, due to differences in overall groundwater residence times and water-rock interaction. Unlike natural water sources, municipal water inputs to urban watersheds peak during the summer (and periods of drought) when natural recharge inputs (precipitation) are minimal or nonexistent. Thus, proportions of natural vs. municipal water sources in the streamflow of some highly urbanized streams vary seasonally, resulting in distinct 87Sr/86Sr and Mg/Ca temporal trends, based on the recharge source. In some urban watersheds, municipal water appears to be a significant streamflow component during dry periods. However, temporal variation in natural Sr inputs to vadose and phreatic groundwater may result in the overestimation of municipal water contributions to streamflow and groundwater recharge during relatively wet periods.Item Management of The Edwards Aquifer: A Critical Assessment(University of Texas at Austin, 1993-08) McKinney, D.C.; Watkins, D.W. Jr