|I very much enjoyed reading this revised manuscript. The authors did an excellent job of responding to reviewer questions and concerns, and I find the paper much improved. |
I still have some (very) minor comments and technical notes that I am sure the authors can easily solve.
1. I suggest a small reordering in the methods and results. In section 2.3.1., I would begin with seasonal patterns of stream nitrate concentrations and then move to diel patterns. (i.e. move lines 109-113 earlier in this section). Same in the results (i.e. move lines 167-176 at the beginning of section 3.1).
2. Looking at Fig. 5, I wonder if it is possible to add some test (i.e. ANOVA) that support your results. This shouldn’t be difficult to do, and it might support your rational.
3. Finally, I still have some minor concerns about the discussion.
First, the section “lateral inputs” is not needed. The first paragraph of this section can easily go to “General patterns”, as the authors talk about how lateral inputs affect longitudinal patterns of stream nitrate concentrations at seasonal scale. Similarly, the second paragraph links nicely to line 308, where the authors say that cluster D might be caused by intense evapotranspiration.
Similarly, I think the section “in-stream vs transport” can easily fit in “interpretation of diel patterns”.
The rational on how evapotranspiration influences diel patterns is confusing. The authors said that intense evapotranspiration can cause cluster D. However, the authors also said that there were no diel patterns of water level, which goes against the previous hypothesis. Please, clarify it.
I did not follow why the relation between Cdiel and water temperature suggest that nitrification denitrification may be the underlying processes. Please, can you develop a little bit more this rational?
Title: “stream nitrate concentration”?
Ln 9. This sentence is quite long. I suggest to start a new one on “We performed a k-means cluster analyses to ....”.
Ln 15. Perhaps add “Results from cluster analyses show that at least 70% …”
Ln 16: “or physical (lateral inputs) processes”
Ln 2. This sentence seems quite off here. I suggest to either move it at the beginning of the introduction or to delete it and simply say “Among the different nutrients, nitrate is of special interest …”
Ln 42. Add here also the hypothesis that diel signals might also be due to diel variations in groundwater NO3- inputs due to evapotranspiration.
Ln 50. Move the ref at the end of the sentence.
Ln 61. “Al our site, “
Ln 66. “gravel bed,”
Ln 88. “in the latter dilution measurement,”
Ln 92. Perhaps is better to indicate which patterns of NO3- concentrations you are referring to. I suggest to change the heading to “Identification of diel patterns in stream NO3- concentration”
Ln 99. Remove “e.g.”
Ln 100. You did a great job here; this reads much clearer now! However, I would perhaps clarify that “diel portion of the solute concentration signal” means “Residuals concentrations”, i.e. add residuals concentrations in parenthesis after “concentration signal”.
Ln 124. Clarify that you did this exercise for both reaches and all clusters. Also, can you add the number of days for each reach separately? If you do so, data would match perfectly with Fig 4.
Lnn138, “Particularly, we assessed daily means of nitrate concentration, water level and water temperature”
Ln 155. Add a comma after “(n=119)”
Lm 166. “stream nitrate concentration”
Ln 172. This rho is negative. So either the symbol is wrong, or the relation between water temperature and daily average nitrate concentration is negative.
Ln 183. “differed between stream reaches and among clusters”
Ln 194. “In both reaches, the time lags roughly ranged between zero and travel time estimates”
Fig 4. Nitpicking, but perhaps it is better to show first the upper reach.
Ln 232: “In our data, we found patterns in stream nitrate concentration”
Ln 238. “On diel scale, “
Fig 6. Nitpicking, but can you highlight the zero line to make it easier for the reader?
Ln 270-274. This rational does not make sense in the current version of the discussion. I suggest deletion.
Ln 281. “, when cluster B prevailed”
Ln 319. “Germany,”