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2007 Ground Water Summit |
Wednesday, May 2, 2007 : 1:20 p.m.
Correct Conceptualization Can Cut Controversy
Models are increasingly being used in the decision making process under scrutiny from regulators and stakeholders having different agendas. Common ground among these entities may be achieved via an agreement on the science. Thus, developing a model that is correctly conceptualized for analyzing the impacts of concern provides objectivity to a study that can be used to create consensus and reduce conflict. Moreover, if a correct science reduces the number of unknown parameters or “work arounds” to solve then additional value is added by reducing the potential number of issues that could lead to disagreement among stakeholders with different agendas or experience. Among the objectives for a groundwater flow model for resource management is to accurately depict water levels in wells subject to interference from other pumping entities. The generally used sink term within a model grid-block to represent well pumping is adequate for a regional analysis of water levels, but lacks the well physics to provide correct drawdown levels locally or capture well interference effects with other wells. An appropriate well module should incorporate details of a well within the regional modeling framework to account for well efficiency effects; well functions that calculate local drawdown and minimize grid-size effects; flow through the well-bore; correct proportioning of flow from each of multiple aquifers or model layers; and supply/demand conditions when aquifers or model layers become unsaturated or go completely dry, as a result of over-pumping or influence from other nearby wells or boundary conditions. Our paper will illustrate the benefits with respect to ease of use and improved accuracy offered by wellbore modules similar to the Multi-Node Package developed by the USGS as compared to the traditional Well Package.
John Waugh, San Antonio Water System John Waugh is director of SAWS, San Antonio Water System.