I have more than 23 years experience in Texas hydrogeology, numerical modeling of water
resources, and studies of water quality for interpreting regional groundwater flow
systems. From 1982 to 2004 I worked at the Bureau of Economic Geology (BEG) at The
University of Texas at Austin on a variety of sponsored-research and usually
multidisciplinary projects. At BEG I supervised graduate research assistants on my
projects and was supervisor or co-supervisor for five M.S. and Ph.D. studies. I joined
the faculty here at UTSA in 2004 and am now supervising three Ph.D. candidates and
two M.S. candidates.
During this research career I have studied the physical and
chemical hydrogeology of several Texas aquifers and have been closely involved in
developing groundwater models for the Ogallala (High Plains) aquifer, Carrizo-Wilcox
aquifer, Edwards (Balcones Fault Zone) aquifer, Gulf Coast aquifer; North Texas
Trinity-Woodbine aquifers, and for alluvial aquifers.
At UTSA I have been teaching two graduate-level courses in hydrogeology:
Introduction to Hydrogeology (ES5603) and Advanced Hydrogeology (ES5703).
I taught Advanced Hydrogeology as a lab-focused groundwater modeling class in which
students learn basic modeling principles but with emphasis on using the USGS code
MODFLOW. The lab sections give the students a working knowledge of three popular
graphics-rich user interfaces for MODFLOW, including Processing Modflow for Windows,
Groundwater Vistas, and Visual Modflow.
RESEARCH
Modeling of Groundwater Resources - Edwards (Balcones fault zone) Aquifer
The Edwards (Balcones Fault Zone) aquifer is a maturely studied karst aquifer
with abundant hydrogeologic data. Detailed information on its karst heterogeneities
remains scant, of course, in comparison to their importance for water transport.
Nonetheless, several numerical models of the San Antonio segment of the aquifer
have been developed for both interpretive and predictive purposes. Since 1979 the
so-called GWSIM model, constructed using the PLASM code,
has been commonly used to simulate groundwater resources in the aquifer. In 2005
a new model of the Edwards aquifer, developed using Modflow, was released (here
named the GWMAP model).
The GWSIM and Modflow models are independently constructed models that differ in
many ways, including but not limited to model cell size, model extent, hydrogeologic
properties; pumping characteristics, and how recharge rates are assigned. The two
models also differ in calibration statistics; the new Modflow model's calibrations
for both hydraulic head and spring discharge generally is improved compared to
those of GWSIM.
Simulation of hypothetical pumping
scenarios representing aquifer-management options shows that the two models give
generally consistent results. Simulated scenarios
included a 73,000 acre-foot/yr reduction in pumping for municipal-water supply from
the San Antonio pool and a 98,000 acre-foot/yr increase in pumping from the Uvalde
pool for pipeline transfer to the big San Antonio municipal market. Scenario
evaluation considered impacts on discharge at Leona, Comal, and San Marcos Springs
and on water levels at the J-17 and J-27 index wells. Consistent simulation results
from multiple independent models provide reliable support policy decisions involving
management of groundwater resources.
Ogallala (High Plains) Aquifer
Carrizo-Wilcox Aquifer
Gulf Coast Aquifer
Paleohydrology and Climate Change
Origin of Brine and Environmental Salinization in Sedimentary Basins
Environmental Assessment at Oil and Gas Exploration and Production Sites
