Source Water Apportionment of a River Network: Comparing Field Isotopes to Hydrodynamically Modeled Tracers
Round 1
Reviewer 1 Report
Dear Authors,
I have now read and reviewed the manuscript: Source water apportionment of a river network: comparing field isotopes to hydrodynamically modeled tracers
The research compare two techniques from two fields of study in order to arrive at estimates of source water fraction within a natural system: One method uses water stable isotope in field-collected samples to build a mixing model, one method uses a calibrated hydrodynamic model with numerical tracers released from upstream reaches to estimate source-water fraction throughout the model domain.
The manuscript shows a good idea of research and certainly provide important information in the use of these methods in hydrological studies. The results look reasonable and is certainly within the scope of the journal. The English language is accurate and the parts are, in general, clear (the topic is tricky, but the authors explain in easy way the subject).
I think is a really good demonstration on application of research tools to solve concrete issues.
However, in spite this information are really useful, in some parts the manuscript need to be revise and some concepts have to be improve.
The manuscript can be published after minor comments.
Line 33-34: I understand the meaning but I am sure that you can rephrase it, and use pollutant/ anthropogenic inputs, instead the word “injected”. I think that injected is inappropriate.
Line 56-57: I think that would be better to deepen the literature on the use of natural tracers/ isotopes in river studies. I am sure that authors can find more information on the use of isotopes in water origin-studies in rivers and streams…some advices:
- Marchina C. et al. (2015). The Po river water from Monviso source to the Adriatic Sea (Italy): new insights from geochemical and isotopic (18O/16O - 2H/1H) data. Environmental Science and Pollution Research
- Marchina, Lencioni (2020). Headwaters’ Isotopic Signature as a Tracer of Stream Origins and Climatic Anomalies: Evidence from the Italian Alps in Summer 2018. Water mdpi.
- Penna D. et al. (2017). Response time and water origin in a steep nested catchment in the Italian Dolomites, Hydrological processes (Print) 31 (2017): 768–782.
Fig. 1: Please, change Agency Gages in gauging station/ agency gauging station. Your term seems to be used in particular in USGS language.
Line 174-174: I am sure that the authors analysed standards and samples in sequence, as indicated by IAEA protocols or in many papers (also cited above). Did these values of 0.6‰ and 0.2 ‰ for ?2H and ?18O related to the only 6-4 injections of the standards during the run? Could you give information about definition of precision and accuracy of these analyses (see Menditto et al., 2007, if need more info)?
Line 268: I am sure that, in this case, my comment above become really important and is better to take into consideration. If you consider the precision of instrument like LGR, standard deviation of the known samples can be lower (but also higher) and normally, precision is indicated by repetition series (not only during the analyses).
Line 355: Here the authors start the discussion that is a well done explanation of the comparison methods. However, is important to insert also a part of Conclusion in a separately chapter or – if the authors prefer- in a chapter “discussion and conclusion”. I think that the second option is more proper.
Author Response
Please see the attachment. Thank you for your comments.
Author Response File: 
Author Response.docx
Reviewer 2 Report
My comments of the manuscript are in the attached file, my concern is especially in the presentation of the manuscript in which I have found several mistakes, for instance several repeated figures.
Other questions and concerns are explained in the text.
As I am not native english speaker, I don't feel qualified to judge the language and style, but I think is apropiate.
Comments for author File: Comments.docx
Author Response
Please see the attachment. Thank you for your comments.
Author Response File: Author Response.docx
