Reply to comment by Kick Hemker on "Evaluation of a pumping test of the Snake River Plain aquifer using an axial-flow numerical model"

Abstract

DOI 10.1007/s10040-003-0250-z The authors regret the omission of a reference to works of Hemker and Maas (Hemker 1985, 1999a, 1999b; Hemker and Maas 1987; Maas 1987a, 1987b). We have recently reviewed several of these papers and experimented with the MLU software for representing a layered aquifer system. We agree with Dr. Hemker that the hybrid analytical-numerical technique developed and described in Hemker (1999a; 1999b) represents an alternative to pure numerical simulation of pumping tests in multi-layered aquifers. The hybrid technique applied in the MLU (Multi-Layer Unsteady State) software developed by Dr. Hemker appears to provide more capabilities than available in the RADFLOW software we selected, including the ability to represent the well as a uniform drawdown (UWD) boundary. In regard to Dr. Hemker’s comment about the citation from Van der Kamp (2001, p. 13). Dr. Hemker is correct, and our citation is inappropriate. As indicated by Dr. Hemker’s comment, Van der Kamp does indicate that both analytical and numerical methods may be applied when multiple aquifers and aquitards are involved. The authors would also like to note that the simulated drawdown patterns displayed in Fig. 8B were inadvertently constructed using a value of specific storage of 3.3e-8 not 1.3e-7 as indicated in Fig. 6. Use of the correct value (1.3e-7 m–1) results in a rightward shift of the early portion of the time-drawdown curve for the lower aquifer.