Inclusion of a Shallow Flow System into Regional Groundwater Model for the Texas Gulf Coast

Presented on Monday, April 29, 2013
Steven C. Young, Ph.D., PG, PE1, Van Kelley, PG2, Trevor Budge3 and Neil Deeds, Ph.D.2, (1)INTERA Inc., Austin, TX, (2)INTERA, Austin, TX, (3)INTERA Inc, Richland, WA

The groundwater availability models available for evaluating management strategies in the Gulf Coast Aquifer System are constructed with large vertical layers that represent a single aquifer.  Because of such thick model layers at the surface,   potential problems can arise with adequate numerical representation of shallow, intermediate and deep flow systems.   The relative importance of these potential problems was investigated by the development and construction of a regional model that covered a 10-county area and overlaps the coverage provided by two existing groundwater availability models for the Gulf Coast. The 10-county regional model  (known as the LCRB model) was constructed to simulate pumping impacts for a proposed LCRA-SAWS water project and it benefited from a well-funded four-year period that included the development of an extensive site conceptual water budget model.  The LCRB model was developed with significantly finer vertical grid spacing, including a model layer to specifically represent shallow groundwater flow.  Comparison of the water budgets from the LCRB model (with fine vertical descritization) and from the two groundwater availability models (with coarse vertical descritization) show order of magnitude differences in the water budgets for a shared calibration period from 1980 to 1999.  The model predictions differ the most in the source of the water for pumping. Whereas the primary source for pumped water for the LCRB model is recharge from precipitation, the primary source for the pumped water for one availability model is river water and the primary source for the pumped water for the other availability model is aquifer storage. The lessons learned from this comparison of regional models demonstrate that the numerical construction of a regional model has a major impact on the capability of the model to properly simulate water budgets and to accurately represent recharge from precipitation and groundwater-surface water interaction.

MP3 Presentation Slides

Steven C. Young, Ph.D., PG, PE
INTERA Inc., Austin, TX
Steven Young has 30 years of experience in characterizing and modeling groundwater systems. Young completed his graduate studies at Stanford University and the University of Waterloo. His expertise includes developing groundwater models and applying parameterization estimation methods to improve the predictive accuracy of groundwater models. He has worked extensively in the Texas Gulf Coast Aquifer System for the last 10 years.
Van Kelley, PG
INTERA, Austin, TX
Van Kelley is a Senior Hydrogeologist with Intera Inc. in Austin, Texas. He has 27 years of experience in groundwater modeling and groundwater characterization experience. Kelley currently is a vice president of Intera and he is the manager of the Intera Water Resources Division.
Trevor Budge
INTERA Inc, Richland, WA
Groundwater model and hydrologist working primarily at the Hanford DOE Reservation.
Neil Deeds, Ph.D.
INTERA, Austin, TX
Neil Deeds is a Senior Engineer at INTERA Incorporated in Austin, Texas, and is registered as a professional engineer in Texas. He received his Ph.D. in Civil Engineering from the University of Texas at Austin. He is part-time lecturer at the University of Texas at Austin in the Department of Petroleum Engineering. In his 12 years at INTERA, he has worked primarily in modeling and analysis of hydrologic systems, with a focus on water resources.
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