Discussion of “Stream Depletion by Groundwater Pumping in Leaky Aquifers” by Vitaly A. Zlotnik and Daniel M. Tartakovsky

Abstract

The authors’ solution assumes that a pumped leaky aquifer is underlain by a source bed that has zero drawdown for all time. However, an actual source bed always has finite drawdown values after relatively long periods of time, and this means that the authors’ solution is valid only for a relatively short period of time after pumping starts. Since stream depletion solutions are almost always used to predict stream depletion values after long periods of time, this means that the solution obtained by the authors is of very limited use. In particular, steady-flow stream-depletion values predicted after an infinite period of pumping in the authors’ solution will always underestimate the actual stream depletion. Unfortunately, this means that their solution is in danger of being misapplied by anyone who wants to justify excessive well abstractions when applying for water right permits. In closing, it is worth pointing out that the equations solved by the authors are identical with Eqs. 18 – 21 in Hunt 2003 if S and in Hunt are replaced with the pumped aquifer specific yield and infinity, respectively. In other words, an appropriate choice of variables allows the Hunt 2003 solution to reproduce the solution obtained by the authors. It would be a misuse of this solution to do so, however, for the reason given above.