--> Abstract: Scaling Up Local Measurements of Hydrologic Properties of the Queen City and Sparta Aquifers, Texas Gulf Coast: Establishing Regional Groundwater Flow Models, by Jean-Philippe Nicot, Neil E. Deeds, and Alan R. Dutton; #90032 (2004)
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Scaling Up Local Measurements of Hydrologic Properties of the Queen City and Sparta Aquifers, Texas Gulf Coast: Establishing Regional Groundwater Flow Models

Jean-Philippe Nicot1, Neil E. Deeds2, and Previous HitAlanTop R. Dutton1
1 Bureau of Economic Geology, The University of Texas at Austin, Texas
2 INTERA Inc., Austin, Texas

Regional numerical models of groundwater flow in clastic aquifers, typically pseudo-three-dimensional with several layers, cannot account for all the complexity of an actual hydrogeological system. Simplifications are inherent but model characteristics should incorporate as much geologic detail as possible. To reflect geological heterogeneity in hydrologic properties, first a correct conceptual model is needed as derived from the analyses of depositional environments. Second, guided by the conceptual model, it is important to scale up hydrologic parameters, in particular hydraulic conductivity, from field measurements to grid-block values.

Texas Gulf Coast aquifers in Tertiary and Quaternary formations share a similar framework. Their sediments were deposited as thick fluvial-deltaic and deltaic sequences prograding toward the shelf margin. The resulting aquifer architecture is a mix of sand bodies with variable water yield and mud-dominated facies of low yield. The Queen City and Sparta aquifers illustrate the methodology. Scaling up is, for example, performed by combining soft data from lithologic maps of net-sand thickness and the hard data of actual hydrologic measurements. Hydraulic-conductivity measurements for these aquifers include several pump-test results and the more abundant specific capacity data compiled from drillers’ logs. Very few specific storage measurements are available from pump tests. Initial estimates of specific storage for model input also are predicted from net-sand thickness maps. Hydrologic data are lacking for downdip locations and therefore parameter values have been extrapolated from the updip trends using empirical relationships.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004