Assessing Stream-Aquifer Connectivity in a Coastal California Watershed
Round 1
Reviewer 1 Report
Paper gives an example of an intensive studied microwatershed in California with the topic to asses stream-aquifer connectivity with different methods. In the Introduction the necessity of groundwater management in this mediterranean climate with groundwater use for irrigation is well described. Novelty is the result on the importance of an aquitard layer in the unconsolidated subsurface alluvium Aquifer. With a set of hydrogeological and hydrological lab and field methods the problem of permeability within the 3-layer structure is analysed in detail. All methods are well described in detail and results are presented in detail with figures and tables. The aquitard has a 2-3-fold less k-values than the main Aquifers, but has a connection with the river bed and deeper groundwater layer, therefore time lags of recovery after pumping of GW-Level is good analysed. To compare lab-, model- and pumping test saturated conductivity (Ksat) is of great interest. Here must be a discussion, which values reflect the reality and does this mean fo a sustainable groundwater use for Irrigation on the farm?
Chapter 3 includes all results in Detail, but no discussion! Authors must include a discussion chapter 4., with: Comparison with other studies in the mediterranean Climate in California (watersheds). Further a discussion on the importance of groundwater recharge and sustainable use of Irrigation water without damaging groundwater-level and dry season stream discharge!
Correct: In Fig. 11 above Ordinate scaling unclear (water-level (m) - 0.0 - 18.0 ???)
Use same unit (feet or meter) in text and figures; do not mix!
Author Response
We have attached here the file containing our responses to all reviewers' comments.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper deals with stream-aquifer interaction at the catchment scale, investigating the effects of groundwater pumping on the stream flow characteristics. The methodology and measures used in this study are wide diffused in hydrogeological studies and even the models are well-known in the scientific world. The article is well written and contains several inspirations for future development of the research.
The introduction contains enough subjects, expect for the general description of stream depletion determination: I suggest to deepen this issue and enlarge the description in order to obtain comparable importance as the analytical models description. In addition, specific objectives of the paper are well and widely described, but, in my opinion, the general purpose is not so apparent (only the last sentence, in fact, seems to put in evidence this aspect). I suggest to be more specific and highlight in a better way the principal aim fo such a study and its specific deliverables and expected applications.
In general, I suggest to express units as in the International System of Units (SI).
In the methods section, some changes are necessary to improve the quality of presentation; in the attached file I've suggested variations and changes. In particular, when you present the tracer tests, some international scientific references are needed as well as the technical notes you reported.
The results are well presented and rather well discussed; some adds are needed and indicated in the pdf file to make the paper more soundly. In particular, in the text you state "The uncertainty due to background fluctuations in dye concentration is relatively high, however, and repetitions of the field tests are needed to conclusively ascribe these observations to stream-aquifer exchange" and for me it is okay, but maybe would be better to explain what you expect from the provided tracer tests and which kind of tests you plan to perform.
Moreover, as concerns Figure 12 d) h) a confidence interval of statistical significance is recommended. The authors can add a significance level of p-value + - 0.05 in the graphs and discuss from a statistical point of view if the peaks observed in correspondence of Frequency 1 and 2 are statistically significant.
The attached pdf contains other corrections and comments
Comments for author File: Comments.pdf
Author Response
We have attached/uploaded a pdf with our responses to all reviewer comments.
Author Response File: Author Response.pdf
Reviewer 3 Report
See the attached file
Comments for author File: Comments.pdf
Author Response
We have attached/uploaded a file of our responses to all reviewer comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Accepted in the present form
Author Response
Thank you for your informative review comments that led to improvements in our manuscript.
Reviewer 3 Report
The authors properly answered most of reviewers' comments. They disagree with some of the comments by Reviewer #3. Here I will refer to those comments only.
Comment #1. This should be carefully considered by the authors.
Comment #2. Under the light of authors' remarks, based on Runkel's paper, a discussion about the use of different tracers in order to directly check the river-aquifer connectivity could be important.
Comment #3. The authors provide a detailed description of the measurement procedure, but the reviewers' question was about variability of measured values among different samples.
Comment #4. Looking at the data positions in the apparent pseudo-sections (Appendix A), it appears that a Wenner-Schlumberger array has been used, not a dipole-dipole array. If this is the case, this would have been a good choice.
Technical comments #3, 8, 21. gpm and cfs are convenient units in the USA, not worldwide.
Technical comment #14. The authors provide a list of references, but the reviewer asked to show more clearly which field data show evidence of tidal effects.
Technical comment #15. This is a scientific manuscript, not a colloquial text ;-)
Technical comment #16. The fact that two quantities show peaks in their spectra at diurnal or semi-diurnal frequency does not necessarily implies that the two quantities are correlated.
Technical comment #22. Correct the sentence "The large drawdown... Figure 11 below" in the caption of figure 10, possibly as "In plot (b), the large drawdown responses (≥ 15 m) in the graph of AG2 levels are due to pumping in AG2. Data in gray box is shown in Figure 11." Similarly for the caption of figure 11.
Overall, the manuscript quality does not reach the threshold for publication on high-quality international journals. Nevertheless it is higher than the average quality of the manuscript submitted and published on Water. Therefore, this work deserves to be published on Water, possibly after minor revision.
Author Response
1.Comment #1. This should be carefully considered by the authors.
Our chosen title is reflective of the study objectives and the results.
2. Comment #3. The authors provide a detailed description of the measurement procedure, but the reviewers' question was about variability of measured values among different samples.
Figure 4 shows variability in data for particle size analyses and permeameter tests conducted on sediment from one of the boreholes. The variability in results of permeability tests is shown in Table 1.
3. Comment #4. Looking at the data positions in the apparent pseudo-sections (Appendix A), it appears that a Wenner-Schlumberger array has been used, not a dipole-dipole array. If this is the case, this would have been a good choice.
Our field notes were consulted based on the comment that a dipole-dipole array may not have been used. In the case of profiles A-A’ and B-B’ a dipole-dipole array was used for data collection and processed into the images in Figure 5 and A1. In the case of profile C-C’ data was collected twice – with both a dipole-dipole array and a Schlumberger Array style. The Schlumberger array data was the one processed for Figures 5 and A1 because data from the dipole-dipole array contained a few obvious spikes in the collected data. We appreciate the reviewer’s detailed examination and have made changes to the caption of Figure 5 to reflect this change.
4. Technical comments #3, 8, 21. gpm and cfs are convenient units in the USA, not worldwide.
We agree, which is why we provide the corresponding values in SI units.
5. Technical comment #14. The authors provide a list of references, but the reviewer asked to show more clearly which field data show evidence of tidal effects.
Again, were refer the reviewer to Figure 12, where the diurnal and semi-diurnal frequency components are evidence of tidal effects.
6. Technical comment #15. This is a scientific manuscript, not a colloquial text ;-)
We see no value in responding to this comment because we believe our choice of words captures the intended meaning.
7. Technical comment #16. The fact that two quantities show peaks in their spectra at diurnal or semi-diurnal frequency does not necessarily implies that the two quantities are correlated.
It does show correlation by definition. We do not imply causality, simply correlation.
7. Technical comment #22. Correct the sentence "The large drawdown... Figure 11 below" in the caption of figure 10, possibly as "In plot (b), the large drawdown responses (≥ 15 m) in the graph of AG2 levels are due to pumping in AG2. Data in gray box is shown in Figure 11." Similarly for the caption of figure 11.
Yes, Figure 10. We include the statement in both Figures 10 and 11 as they show the same data.
Overall, the manuscript quality does not reach the threshold for publication on high-quality international journals. Nevertheless it is higher than the average quality of the manuscript submitted and published on Water. Therefore, this work deserves to be published on Water, possibly after minor revisions.
