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2007 Ground Water Summit |
Monday, April 30, 2007 : 1:20 p.m.
Making the Most of a Simple Model: Using Extensive Data Sets and Parameter Estimation to get Basin-Scale Insight on Changes to Outcrop Recharge
Coal-bed methane (CBM) development in the San Juan Basin has required water extraction from the Fruitland formation. One critical question regarding the water extracted is whether it will have a significant impact on surface waters. For example, will rivers crossing the Fruitland-formation outcrop experience significant depletion? The Theis equation and Glover-Balmers’ reformulation were used as models to (1) determine basin-averaged hydrologic parameters of the Fruitland formation, and (2) quantify the impact of CBM-water extraction on streams crossing the Fruitland formation outcrop. Water production from more than 1600 CBM wells and observation data were used to constrain an automated parameter estimation routine (PEST) and determine the best-fit hydrologic parameters. Superposition of impact from each of the 1600 wells provided an estimate of impact on the Fruitland-formation outcrop. The simple models and PEST efficiently incorporated large datasets into the determination of impact estimates. Despite their simplified representation, the analytical models provided reasonable estimates of parameter values, in close agreement with a series of previous, far more complex, modeling efforts.
Gilbert Barth, Ph.D., SS Papadopulos and Associates Dr. Barth received his doctorate working with Tissa Illangasekare and Mary Hill. He completed a National Academy of Sciences, post-doctoral fellowship at the U.S. Geological survey. Since the post-doctorate he has worked in consulting, with SSPA since 2003. His emphasis in more recent years has been on assessing the sensitivity of riparian zone and surface water/groundwater interaction to anthropogenic changes.