Promising new baseflow separation and recession analysis methods applied to streamflow at Glendhu Catchment, New Zealand

Stewart, M. K.

doi:https://doi.org/10.5194/hess-19-2587-2015

Articles | Volume 19, issue 6

https://doi.org/10.5194/hess-19-2587-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/hess-19-2587-2015

© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 19, issue 6

Research article

|

02 Jun 2015

Research article |

| 02 Jun 2015

Promising new baseflow separation and recession analysis methods applied to streamflow at Glendhu Catchment, New Zealand

M. K. Stewart

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Final revised paper (published on 02 Jun 2015)
Preprint (discussion started on 27 Jun 2014)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC C2800: 'Review', Anonymous Referee #1, 30 Jul 2014
RC C3535: 'Review of "New base flow separation and recession analysis approaches for streamflow" - hess-2014-219 - by MK Stewart', Anonymous Referee #2, 01 Sep 2014
AC C3963: 'Author's Reply to Anonymous Referee #1', Michael Stewart, 22 Sep 2014
AC C3964: 'Author's Reply to Anonymous Referee #2', Michael Stewart, 22 Sep 2014

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (20 Oct 2014) by Jim Freer

First I thank the reviewers and the author for their very useful correspondence on this paper. I believe the editors have made some clear points that need to be addressed in the final manuscript and if this would be acceptable for publication in HESS. From the reviewer comments and author responses I suggest the following that include some major changes:
1) I agree the manuscript needs to be made more readable. I agree that reviewer 1 has covered most of the areas that need attention. The author says he will work on these and that will need significant improvement in the manuscript
2) I agree the technical elements of the paper need better development. This goes hand in hand with other comments made by both reviewers about the general applicability of this method. I do have some sympathy that the title is miss-leading and I do feel the case has not been made about how the method has utility across a range of catchment types. I do feel if these are not addressed (with further studies) then a modification to the title will be appropriate. I would argue a minimum of 3 catchments of different scales and behaviour would be appropriate to state that the method has been properly explored as a general approach and any shortcomings identified (or that the approach can be successfully applied)
3) I agree the literature does not appear to be adequately followed by the author and this does need improvement. There are other papers I have already mentioned (Lamb et al. being one), others by Martyn Clarke and all are exploring recession methods. This generally needs to be improved throughout
4) There are a number of comments from Reviewer 1 that again criticism the utility about the method and again this is because the method has been applied to one particular catchment. The emphasis and title of the paper will need to be re-written if the author cannot apply this to additional catchments as there is little discussion of the dangers of suggesting a method without further exploration and if experience and data needs will mean general applications will not be possible or easy
5) Most of the minor comments from reviewer 1 appear to be well covered by the author
6) I think what reviewer 2 is driving at is that the methods application is one catchment and a nice detail of that analysis has been conducted by the author. I agree the title reads as if this is a method for general applicability, but this has not been demonstrated and in fact is not discussed in this way in the conclusions. To state that approaches are misleading cannot in essence be based on one catchment unless that is clearly clarified in the context of the paper. No such discussion is currently generated. I would argue more a title like. A promising new base flow method and recession approach for streamflow applied at one catchment in New Zealand - could be more appropriate for example
7) I do agree the justification of why base flow recession should be applied first and the linkage to other methods deserves more attention. The difficulty again is the evidence base of one catchment in confirming this and the author needs to get this right in the context of the one study they provide. I appreciate the long response from the author on this and good points are made, I will look out for ensuring the right balance in this discussion is made int eh final manuscript

Can I note I will send this manuscript out for further review after the next major correction of this manuscript are obtained, best wishes

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AR by Michael Stewart on behalf of the Authors (16 Dec 2014) Author's response Manuscript

ED: Referee Nomination & Report Request started (12 Jan 2015) by Jim Freer

RR by Anonymous Referee #1 (13 Jan 2015)

RR by Anonymous Referee #2 (20 Mar 2015)

Suggestions for revision or reasons for rejection

Review of “A promising new baseflow method and recession approach for streamflow at Glandhu Catchment, New Zealand” by M.K. Stewart

This is a much revised manuscript following earlier reviewer and editor comments. I found the revised manuscript somewhat improved in structure, but several oddities remain (e.g. subsection 2.2.1 begins mid-paragraph “However,……”). Despite the restructuring and new sections that have made this a somewhat different paper with a modified title, the author has not addressed the fundamental problem with the manuscript: the tone of presentation in the paper. It remains a set of sweeping statements that dismiss recession analysis techniques and baseflow separation as being “in disarray”, and then draws broad conclusions based on two hydrograph events – a total of only 16 days of data from a 2.18 km2 watershed, and declares very simple empirical model as being “more accurate” than previous methods, but compares this model with a very limited subset of the available approaches, extols the few advantages of the new method but grossly underplays its limitations. It is not reasonable to evaluate the general utility of an empirical model that was derived from two hydrograph events, in a very small watershed, by measuring that model’s ability to reproduce the very responses from which it was derived!

The manuscript’s sections that focus on the field site and analysis of the data are much improved in terms of clarity, but the presentation of the results, is severely compromised by the framing of the manuscripts central arguments as set out in the abstract and introduction. Broadly speaking:

(1) That there is no general consensus on how to approach the problem of baseflow and recession analysis, even though there are many different methods available for each;

The author does not really provide a thorough review of this area, but makes sweeping statements based on selected quotes from previous papers, many of which were written 20 to 50 years ago when methods were considerably less advanced than they are now. Because of this, many key references are missing, and there is no detailed consideration of the methods – yes, the methodology states some of the approaches, but the treatment is not in any depth. The author criticizes a lack of consistency in approaches, but does not provide the detailed level of analysis to illustrate what distinguishes the different methods – what assumptions underpin each approach, why are they necessary, and what is their potential impact on the results? All analysis of baseflow and recession curves requires a set of assumptions, and the results will depend on what assumptions were made. The introduction doesn’t provide anything but a very selective overview that is highly dismissive of the available approaches and fails to consider the technical background that would allow a meaningful discussion of differences to be made. These opening paragraphs have an effect that totally undermines the potentially interesting results from Glendhu, because it frames the whole manuscript as the search for a solution to the question of how to do baseflow and recession analysis, rather than using them as a way to demonstrate how a particular model might be used in particular circumstances.

The present manuscript now states several methods, but it does not really evaluate them in a critical and meaningful way that would allow a balanced evaluations of their relative merits and the uncertainties likely to result in any analyses or subsequent interpretation. Without such a detailed view it is simply impossible to say that one approach is “better” than any another.

(2) That performing recession analysis prior to baseflow separation can be highly misleading;

Can it – I am sure it can, but under what conditions, in what sort of watersheds, for what kind of events? That sounds like a very interesting question! This is simply stated by the author – and I expected it to be followed by a detailed analysis to prove the point, but there is no evidence or illustrative discussion presented to support the assertion. This is simply the author’s opinion and is stated on line 91 “whilst this may be considered obvious by some”… This statement appears to fundamentally misunderstand why a mathematical analysis is done in this order – but the logic is carefully described by Eckhardt (2005), such that the comments in lines 91-92 just appear naïve and dismissive. If the author wants to advance the notion that such procedure is a big problem, then he must provide evidence for why that is the case – not simply state that it is obvious, because it frankly it isn’t. I agree that a constraint of digital filters is that several assumptions must be made, one of which enables the separation of baseflow from rapid runoff through the identification of a baseflow recession parameter during a period of assumed zero rapid runoff, by selecting a period when there is no incident precipitation, but when the streamflow continues to recess. It is perfectly valid to question that assumption, but to do that requires empirical evidence or a theoretical model to explain why this approach is subject to uncertainty!

(3) that applying baseflow separation analysis before recession analysis can resolve some problems with recession analysis and provide new and important insights into catchment water storages; and,

This point follows from (2) above. But again, this is just stated, without any evaluation of a substantial body of evidence to support the statement – except 16 days of data from Glendhu! I don’t disagree that there are potential problems with performing the analysis in the way that most digital filters do, but to argue this point convincingly requires a very detailed analysis of the way in which the underlying assumptions impact on the resulting analysis- which is not presented.

(4) the new “bump and rise” baseflow separation method provides “more accurate” baseflow simulations than previous methods.

The manuscript uses two sets of sampling data – one from a 2-day period in 1988, and one from a 14-day period in 1996 – and uses these, along with the simplest of all baseflow separation methods developed in the late 1960s (the Hewlett and Hibbert (1967) approach) to develop the “bump and rise” method for the Glendhu catchment – area 2.18 km2. The results of this new model, derived from 16 days of observations in a 2.18 km2 watershed are then declared as universal truths – the conclusions do not frame the findings of the study with any degree of caution given their very limited representation of processes. There is undoubtedly an interesting story from Glendhu, but it cannot be reported in the way of this manuscript. It is too emphatic, and does not command such direct and forthright conclusions!

I think the author has an interesting contribution to make – there are some interesting sample data from the Glendhu catchment that show the watershed to have some interesting characteristics, albeit from limited data. It is entirely reasonable to present this, and to use some simple analysis to suggest the mechanisms of streamflow generation that occur in this (and possibly other) small catchments. However, the manuscript as it stands is an entirely inappropriate framing of a very limited dataset, from a very small watershed, used to produce a very simple model which is subjected to very little scrutiny within the context of alternative approaches.

For these reasons, I do not think this manuscript should be accepted for publication in HESS. This is because there is no scientific argument elucidated to justify the utility of the BRM method over existing (and generally-used) approaches.

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ED: Publish subject to minor revisions (Editor review) (07 Apr 2015) by Jim Freer

AR by Michael Stewart on behalf of the Authors (16 Apr 2015) Author's response Manuscript

ED: Publish as is (12 May 2015) by Jim Freer

AR by Michael Stewart on behalf of the Authors (22 May 2015)

Short summary

This paper presents new baseflow separation and recession analysis methods for streamflow. The baseflow separation method ("bump and rise method" or BRM) aims to accurately simulate the shape of tracer-determined baseflow or pre-event water. The recession analysis approach advocates analyzing quickflow and baseflow as well as streamflow because analyzing the latter alone gives misleading information on catchment storage reservoirs. The methods are demonstrated for the Glendhu streamflow record.