2016 NGWA Groundwater Summit

Estimating Hydraulic Properties with Stress-Specific Groundwater Models

Wednesday, April 27, 2016: 11:50 a.m.
Confluence Ballroom B (The Westin Denver Downtown)
Keith J. Halford, Ph.D. , U.S. Geological Survey, Carson City, NV

Creating multiple simple, groundwater-flow models that simulate different stresses is a reliable approach for estimating hydraulic properties where different levels of discretization are required.  Multiple models are faster than a single integrated and complex model because specific problems are addressed with each model.  For example, steady-state flow, water-level declines from groundwater development, and responses to regional-scale aquifer tests frequently require different levels of spatial and temporal discretization. These requirements can be addressed quickly and correctly with three separate flow models with identical hydraulic-property distributions. Steady-state water levels and spring discharges can be simulated with a steady-state model. Water-level declines and spring captures can be simulated with groundwater-development and regional-scale, aquifer-test models.  Differences between all simulated responses and corresponding measured water levels, spring discharges, water-level declines, and spring captures are minimized simultaneously. Efficacy of this approach is illustrated with examples from the Death Valley region. Death Valley groundwater-flow models were created and calibrated rapidly where hydraulic properties are distributed with pilot points and geologic preferences are constrained with Tikhonov regularization.  Hydraulic conductivity and specific yield distributions were estimated with three numerical flow models that simulate different stresses and share common hydraulic-property distributions.

Keith J. Halford, Ph.D., U.S. Geological Survey, Carson City, NV
Keith Halford is a research hydrologist at the U.S. Geological Survey and has served as Hydrologist and Groundwater Specialist in California, Florida, and Nevada offices of the USGS since 1987. He wrested a Ph.D. in petroleum engineering from Louisiana State University. His areas of expertise are aquifer tests, borehole geophysics, geostatistics, groundwater simulation, and parameter estimation. Developing methods and software for modeling water levels to estimate drawdowns has been the focus of recent publications.