Flow Division Dynamics in the Mekong Delta: Application of a 1D-2D Coupled Model

Round 1

Reviewer 1 Report

General comments:

A lot of data. Valuable data, if the authors will chose to synthesize the text.

This paper can be redesigned.

Some information can be synthesized in tables.

Introduction section: well written

Methods, for example, are presented like a huge story. Please use some tables to present you available data/materials and methods.

Sometimes methods are mixed with results and results are mixed with methods, please reconsider this aspect.

Please use some tables to present your results, again...here is a big ”story” very hard to follow.

In Disscussion section you can present also, in some paragraphs the situation during the wet season.

If the authors will rewrite their rmanuscript, this paper can be shortened and can be easy to follow.

A long list of references.

Graphical illustration well designed.

The authors should highlight more their own results.

This manuscript can be published if the authors will consider reviewers comments and suggestions.

Author Response

General:

The manusript addresses various physical processes within the Mekong Delta. The graphics (fiugure and tables) constitute nearly 11 pages of the total manuscript. Thanks to the constructive suggestions of the reviewer, we have reduced the total word count of the body text from 8490 to 6498 (23% reduced). We have added two tables and extended a results section table to simplify various parts of the article. 

Reaction to specific negative comments:

“Methods, for example, are presented like a huge story. Please use some tables to present you available data/materials and methods.”

The Methods section now consists of: 2.1. Approach 2.2. Model Description 2.3. Model set-up 2.4. Timeseries analysis 2.5. Model calibration and validation. The general approach to answer research questions are mentioned bullet-wise in section 2.1 (to avoid repetition). The data/material section and model set-up are merged into one section and a table is added to summarize all the data used in the study. The textual explanations of Model Set-up and Model calibration sections are reduced.

“Sometimes methods are mixed with results and results are mixed with methods, please reconsider this aspect. ”

While we are not sure if in all occasions we are synchronized with the reviewer in identifying this discrepancy, we have moved various parts from the results section to the methods section, which also helped reducing the length of the article. However, there are certain observations in the calibration part that may seem as results, but we find them important considerations during model calibration. An example is explanations on subtidal water level wave propagation upstream.

“Please use some tables to present your results, again...here is a big ”story” very hard to follow.”

We simplified the textual explanations throughout the results section. merged tidal propagation and the effect of irrigation system into one section and specifically extended the table in the sensitivity analysis to summarize the findings. This makes it much easier for the reader to understand the main findings of every simulation. However, please keep in mind that we are addressing 3 different but inter-connected physical processes in the same paper.

“In Disscussion section you can present also, in some paragraphs the situation during the wet season.”

Under every section of the discussion chapter we have added comments on the relevance of our findings to the wet season. However, this remains limited since the wet season dynamics are largely influenced by flooding which we did not address in our modeling practice and it demands a complete study.

“If the authors will rewrite their rmanuscript, this paper can be shortened and can be easy to follow.”

The textual explanations are reduced by 23%.

“A long list of references.”

We tried to reduce the number of references and reduced them by 10%.

Please note that on three different issues addressed in the paper, a literature review was needed to develop the context. Furthermore, on every issue the findings are assessed in the context of the previous literature, which amounts to a large number of citations.

“The authors should highlight more their own results.”

We have addressed this issue throughout the paper and specifically under the Discussion section. We reduced the discussion section to 1) the effect of irrigation system on tidal propagation,  and 2) temporal and cumulative discharge division. In order to simplify comparison with previous studies we added a table that helps reducing the textual explanations and pointing the readers to the main differences.

Reviewer 2 Report

Please see attached document.

Comments for author File: Comments.pdf

Author Response

Reaction to the comment on Figure 4.

We added text in the Methods section referring to the qualitative nature of this figure and added additional explanations in the limitations section (Discussion). Please keep in mind that although quality of available gauge, morphology and geometry data in Cambodia is questionable, we came to the conclusion that the qualitative calibration still had an important role to the overall model accuracy and this is nevertheless the best data available (to our knowledge). 

Furthermore, this is a comparison that is hardly ever presented in the existing modelling studies of the Mekong Delta (e.g., 8, 10, 23, 24). We decided to still present this qualitative representation of the Cambodian channels, in order to raise attention for other modelling exercises. Having said that, the good calibration and validation of the model within the Vietnamese Mekong Delta pertains to limited impact of the observed discrepancies on tidal dynamics within the VMD.

Reaction to the comment on Figure 5.

There is an offset in the average water levels, which translates into a slower propagating wave (smaller depth) and shows itself as a phase lag of about 20deg in various tidal constituents.

As Chau Doc share of discharge  is 15% (model and observations match), tidal water level amplitude is about 50% of Can Tho, and tidal discharge is only 10% of Can Tho, we believe that the 20deg phase lag of the model "in this stretch of the channel", is not significant in understanding the overall physical processes we try to address; namely, 1) the role of the irrigation channels 2) temporal and cumulative discharge, and the role of subtidal water level variations on discharge division.

Reaction to model validation and application of Transfer Entropy:

In this paper, we applied widely-used modal validation indicators to calibrate the model.

Nevertheless, we do acknowledge that it is an interesting additional measure for model validation that can be considered in the next stage of this study when we add other processes to the same model. At this stage, since the model is showing an acceptable performance, we expect using additional validation indicators will probably not influence the outcome of the study.

Round 2

Reviewer 1 Report

You synthesised in clear form your manuscript. Especially, Methods and Results Sections.

You shortened you text and focused on main issues and introduced sub-sections and synthesizer tables. It is easy for the reader to follow your ”red wire”.

It is worth to be published.

Congratulations for the amount of work and graphic illustration.

Author Response

Many thanks for your review and fruitful suggestions along the way! 

Reviewer 2 Report

Minor edits:

Line 305,314,417: States "Error! Reference source not found." Please correct.

Results section goes from Section 3.1 to 3.3. Please correct.

Author Response

Dear Reviewer,

The mentioned errors on cross-references and section numbering are now corrected.

Many thanks for your constructive review and suggestions along the way!