Reply to Comment on "Sensitivity analysis and determination of streambed leakance and aquifer hydraulic properties" by S. Christensen

The study of Christensen [Christensen, S., 2000. On the estimation of stream flow depletion parameters by drawdown analysis. Ground Water 38 (5), 726-734], based on the solution of Hunt [Hunt, B., 1999. Unsteady stream depletion from groundwater pumping. Ground Water 37 (1), 98-102], analyzed three streamflow depletion parameters T, S, and λ of a simplified stream-aquifer system. Although such a stream-aquifer hydrologic condition does not commonly exist in the real world, Christensen [Christensen, S., 2000. On the estimation of stream flow depletion prameters by drawdown analysis. Ground Water 38 (5), 726-734] concluded that his results can be used to analyze any hydrogeological setting and his proposed methodology can analyze any possible pumping test design. Stream-aquifer-well systems are far more complex in the real world: lack of a semipervious layer that covers the whole stream channel, anisotropic hydraulic conductivity of stream sediments and the surrounding aquifers, effects of multiple channels or stream width, etc. It is clear that the results of Christensen [Christensen, S., 2000. On the estimation of stream flow depletion prameters by drawdown analysis. Ground Water 38 (5), 726-734] have limitations in the analyses of streamflow depletion parameters. It is then very apparent and logical that further research on streamflow depletion parameters for a more complex stream-aquifer system and for a less ideal design of pumping and observation well network is needed. Chen and Chen [Chen, X.H., Chen, X., 2003a. Sensitivity analysis and determination of streambed leakance and aquifer hydraulic properties. Journal of Hydrology 284, 270-284] used numerical models to simulate stream-aquifer interactions and fullfilled at least part of this need. The study of realistic and complex stream-aquifer-well conditions on streamflow depletion parameters remains an important topic of research.