Interactive comment on “Nitrate removal in a restored riparian groundwater system: functioning and importance of individual riparian zones” by S. Peter et al

substantive issue with the paper is the low sample sizes. For example why is only data from 1 piezometer used to average discharge conditions (page 6724, L24)? However, the authors provide chemical, hydrology, isotope, and genetic data to make their case all of which seem to point in the same direction. It’s very interesting to note that while the willow zone is most efficient, the forest zone contributes greatest to N removal. The results beg the question of “what is so great about willow zones that makes them so good at removing N”. The authors suggest that willow contributes organic carbon to the substrates that fuel denitrification. That may be true, but willows grow where hydrologic conditions are conducive because they require flooding and generally wetter conditions. So, the authors should not exclude the possibility that the willow zones are unique hydrologic features of the river ecosystem. Furthermore, suggesting to grow willow to increase N removal in restored riparian zones will be dependent upon creating the proper hydrologic conditions. In other words, willows will not grow just anywhere.