Gulf Coast Association of Geological Societies Transactions
Volume 54 (2004)

EXTENDED ABSTRACT: Scaling up Local Measurements of Hydrologic Properties of the Queen City and Sparta Aquifers, Texas Gulf Coast: Establishing Regional Groundwater Flow Models

ABSTRACT

Regional numerical models of groundwater flow in clastic aquifers, typically pseudo-three-dimensional models with several layers, cannot account for 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, a correct conceptual model is first needed, as derived from analyses of depositional environments. Second, with the conceptual model as a guide, it is important to scale up hydrologic parameters, hydraulic conductivity in particular, from field measurements to grid-block values.

Texas Gulf Coast aquifers in Tertiary and Quaternary formations have a similar frame-work. 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. We have chosen Queen City and Sparta aquifers to illustrate our methodology. We performed upscaling by combining soft data from lithologic maps of net-sand thickness and hard data from 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 are also predicted from net-sand thickness maps. Because hydrologic data are lacking for downdip locations, parameter values have been extrapolated from the updip trends using empirical relationships