Conceptual Model Report: Minor Aquifers in Llano Uplift Region of Texas


Link to Full Text

Download Full Text

Publication Date

March 2016


The Texas State legislature mandated that the Texas Water Development Board (TWDB) obtain or develop groundwater availability models for all major and minor aquifers in Texas. To develop a groundwater availability model (also known as a numerical groundwater flow model), a conceptual groundwater model must be constructed first and lays the foundation for the groundwater availability model to be built upon. A conceptual model is a simplified version of the “real world”, which the groundwater availability model can handle through a computer program. This report summarizes a groundwater conceptual model developed for the minor aquifers (the Hickory, Ellenburger-San Saba, and Marble Falls) in the Llano Uplift region. The minor aquifers defined by the TWDB in the study area occupy an area of 8,764 square miles in nineteen counties: Blanco, Brown, Burnet, Coleman, Concho, Gillespie, Hays, Kendall, Kerr, Kimble, Lampasas, Llano, Mason, McCulloch, Menard, Mills, San Saba, Travis, and Williamson. Both the Hickory Aquifer and Ellenburger-San Saba Aquifer contain outcrop and downdip portions, while only the outcrop portion of the Marble Falls Formation was defined as official aquifer by the TWDB. This conceptual model provides the geologic framework and interpretation of the groundwater flow system within in the study area. This initial evaluation includes information concerning climate, physiography, geology, previous studies, hydrostratigraphy, water levels and groundwater flow, recharge, surface water features, hydraulic properties of the aquifers, discharge (such as pumping from wells), and water quality. The conceptual flow model for the Llano Uplift region contains seven hydrostratigraphic units including four aquifers (from top to bottom): the Cretaceous aquifers, Marble Falls Aquifer, Ellenburger-San Saba Aquifer, and Hickory Aquifer. Separating the aquifers are three confining units. All seven units are discontinuous. The top and bottom of the conceptual model domain are the ground surface and the top of the Precam


Conceptual Model Report, Minor Aquifers, Llano Uplift Region, Texas

Document Type