- © 2000. AAPG/DEG
Unlike the Neuman solution (1974), the Dagan solution (1967) neglects elastic storage of unconfined aquifers. Whereas the former has been commonly used in the analysis of aquifer pumping tests, application of the latter to determination of aquifer parameters are rare. This article evaluates the reliability of the Dagan solution (1967) for the determination of the horizontal and vertical hydraulic conductivity Kr and Kz and specific yield Sy by neglecting the role of aquifer storage coefficient S. To be consistent in the analysis of aquifer test data, the Dagan solution was combined with an inverse computational procedure so that Kr, Kz, and Sy can be automatically calculated. Computations converge relatively fast because evaluation of the Dagan solution is mathematically simpler than is the Neuman solution. Data from three pumping tests conducted in alluvial aquifers in the Platte and Republican River valleys, Nebraska, were analyzed. Earlytime drawdown data from the site in the Platte River valley are scarce, but plenty of early-time drawdowns were collected from the two sites in the Republican River valley. Comparison of the results from the Dagan and the Neuman solution indicates that the Dagan solution provides aquifer parameter values very close to those of the Neuman solution in most situations. For most practical purposes, the Dagan solution is as good as the Neuman solution for aquifer test analysis.
Key Words: unconfined aquifer, hydraulic conductivity, storage coefficient, aquifer test.
Xunhong Chen is an associate professor and research hydrogeologist with the Conservation and Survey Division at the University of Nebraska–Lincoln. He received his Ph.D. from the University of Wyoming. His current research includes groundwater modeling, aquifer tests, and stream–aquifer interactions.