Minimum Residual Flows for Catchments in the Czech Republic

Round 1

Reviewer 1 Report

The paper presents a new methodology of determining the minimum residual flow of rivers in the Czech Republic. In my opinion the study deserves attention and can be published in the journal. However, there exist some shortcomings, which require improvements prior to the final acceptance of the submission for publication. These are as follows:

1. Chapters 1 and 2 should be redrafted. Parts of the text related to the study area need to be moved from chapter 1 to chapter 2 (“Study area and Data”). Figures 1 and 2 should also be moved to chapter 2. Moreover, a description of hydrology of the study area should be added.
2. Figure 1: besides the map of the average annual precipitation, a map showing the spatial differentiation of flow would be useful.
3. Figure 2: these are not trends, but the multi-annual course of these variables. In my view, the red curve is probably not a moving average, but the average of all flows in the following years (values shown in grey, from 334 water gauges). How many meteorological stations with precipitation records are shown here?
4. Figure 3: “DMR 4G” the units are lacking. I am guessing it should be “m a.s.l.” (meters above sea level). Please correct.
5. Lines 52, 140, 141, 198, 199, 201, also Table 1: please correct the notation from “m³/s” into “m³·s^-1” in through the whole text.
6. Figure 5: the quality needs to be improved: the axes labelling is too small and thus unreadable – please enlarge. There is a lack of legend explaining what the respective box-whisker plots show. Perhaps it would be better to change the figure captions “a” and “b” from “Ratio…” into “The range of ratio changes…”.
7. Figure 8: the country abbreviations (CR, GB, BAV – by the way, it is not an individual country, SUI) should be explained in the text and also in the figure caption. Moreover, please note that “the United Kingdom” should be abbreviated as “UK”, not “GB”. Please correct.
8. Figure 8: in my opinion the vertical axis Qa should be marked with [m³·s^-1]. Please check.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript provides an overview of the development of a new approach to estimate minimum residual flow (MRF) in the the Czech Republic. Unfortunately, under the overview, the details of the content are not well organized and confuse the readers.

Throughout the entire manuscript, variables are used and discussed without clear definition. Examples are MRF (which is the key of the paper so a clear definition should be provided), ecological flows, long-term average minimum flow (not clear over what window, at what sampling frequency, etc.), minimum ecological flow, weighted usable area, the variables in Figure 8, and variables such as Q95, Q97, etc., which are not defined upon first appearance. Use of symbol is not consistent in some Figures and captions (e.g., Fig 7).

The methodology section does not provide clear explanation either. For example, how are the thresholds for K99 in section 3.1 defined? The whole process of IFIM and PHABSIM is skipped: the shortcomings are mentioned but not discussed, the methodology is not explained at all, the optimum minimum flow (line 178) not defined, and the assumption on line 188 about the MRF (which would be the key contribution of the study) is based on authors' assumption that is not justified. The determination of coefficient K also not justified.

Lines 231-232 are misleading as more than half of the data points in area 4 is below roughly 1.6 (Fig 5a).

As a whole, the manuscript does not provide a clear justification and explanation of the method, and does not have a clear research objective, which limits the scientific significance of the study.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Paper presents a very interesting concept for the calculation of the biological minimum of the flow for the Czech Republic. I prefer such real case study analysis, with comparing the obtaining values for all other countries. I am suggesting a minor revision.

Authors stated that the presented formula/method is in negotiation with Czech authorities. I believe there is some criticism, i.e. lacks of the presented method. Authors should say something more about it.

Also, comment(s) about application of presented method in all other countries should be written. 

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The comments have been addressed.

I suggest one more round of thorough proofreading throughout the entire manuscript:

1) Every variable should be properly defined upon first appearance (e.g., the pi in eq 4; it has a subscript so I'm assuming it's a variable)

2) Make sure to have consistent and unambiguous use of variables and subscript (e.g., in equation 4 there's no explanation on subscript j, and the capital K, and if x=1 then why does it need to be shown)

3) Spell check and grammar check. For example, line 52 "... surface water, which ....": the comma makes a huge difference in the meaning, so please double check.

Author Response

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Author Response File: Author Response.pdf