Impact of Coastal Wetland Restoration Plan on the Water Balance Components of Heeia Watershed, Hawaii

Round 1

Reviewer 1 Report

HYD-951171 “Impact of coastal wetland restoration plan on the water balance components of Heeia watershed, Hawaii” KA Ghazal, OT Leta, AI El-Kadi, H Dulai

This article describes the use of the SWAT model for estimating the water balance components of a watershed in Hawaii. It is generally well written, and has a solid story to tell, although the lack of variation in the irrigation scenarios suggests the variations are not modelling the most important factors.

It is not necessary to have both a calibration and validation period when you are not performing speculative future predictions or sensitivity analyses, but only comparative land-use simulations with the current climate state. Using all available data allows for the greatest range in response and therefore the model has fit/compromise all observed behaviour.

Section 2.3 is a single sentence. That is ridiculous. Just use it as the first line of (new) Section 2.3 (combined with S2.4) and renumber the sections.

Figures 1, 2 and 3 are very dense, and have too many categories (10 to 14!) for simple black and white gray-scales. The text is very small and barely readable; again too many categories and too many words in the figures. They need some simplification or be made into full page figures so they can be clearly seen and interpreted.

Similarly Figures 4 and 5 have a lot of lines and shaded area, most of which is very close to the x-axis, making it difficult to see. Perhaps using cumulative total streamflow with observed on x-axis and modelled on y-axis, with a 1:1 line marked, would more clearly show the model performance.

Do the authors have any knowledge of older land uses on the island of Oahu? What are the WBCs for native vegetation and wetland only? What are the WBCs for native cultivation in pre-European conditions? How would they compare to the proposed revegetation and the current situation of california grass? What are the land-use conditions of the baseline scenario?

The authors mention on page 14 that S2 gives the necessary flooding for taro cultivation. Given there is little difference in WBC between S1 to S4, did the other scenarios also yield enough water for taro?

Author Response

We thank the reviewer for providing thoughtful and constructive comments to further improve the quality of the manuscript.  The responses to each comment are provided below.

• While we agree with this comment, but we split the available streamflow data into calibration and validation periods to evaluate the performance of the model outside the calibration period and ensure representation of simulated streamflow values, which have been used for water diversion and taro irrigation.
• Done (see section 2.3 & pages 8-9).
• Done (see Figures 1, 2, and 3). Please note that figure 3 is more simplified to increase its readability.
• Since we wanted to show the model prediction uncertainty along with simulated and observed streamflow values, we enhanced the visibility and clarity of the graphs by removing the rainfall panels and increasing the figure heights (see Figures 4 and 5). We hope this much improved the readability of the figures.
• The baseline and pre-development land uses are shown in Figures 1 and 2. We also provide sources of historical land use on Oahu Island (see Page 3, lines 105-107). While the comment on WBCs is much appreciated, we were not able to find a specific WBCs for native vegetative and wetland of pre-European conditions to make a comparison with the current values.
• We agree that the four scenarios (S1 to S4) did not show a significant difference in yearly WBC (Table 6) due to ample water during the wet season and thus setting minimum flow values might not be reflected on WBCs. However, a difference is noticed on seasonal WBCs especially during the dry season where short of water and setting an irrigation minimum flow have a significant role (Table 5). In addition, the impact of irrigation water diversion on downstream flow values is noticeably observed in Figure 9. Overall, while all scenarios were able to divert enough water for taro, S2 provides sufficient water to taro during the dry season without much compromising both downstream streamflow value and riverine ecosystem health (see page 26, lines 419-432 for detail).
•  

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

The paper is nicely written, and the subject is of interest to the Hydrology Journal readers. The method applies to other regions of the world for similar studies, and it is sufficiently explained and discussed based on existing literature. I ran a plagiarism check on the document, and I've just found out is the main result of the Ph.D. dissertation of the main author. Congratulations.
My comments related to the minor revision I am asking:

1) FIGURES 2, 3 & 7: Even if the maps are clear enough, a good practice is to include the coordinates in the frame, as many readers (including myself), like to have an idea of where is the case study, without having to stop our reading. See an example: https://www.ecologyandsociety.org/vol21/iss1/art39/figure1.html

2) You can merge sections 2.3 and 2.4, perhaps naming this new section "SWAT model setup" and extend just a little the your SWAT definition, as it does not mention nothing about soil, water, GIS or anything. I know the 99% of the readers of the paper would have an idea of what SWAT is,  nevertheless, it makes for an easier reading.

3) Some small editing that could easily be addressed in the proofread, e.g., the extra spaces at the beginning of section 3.2 and before the caption of Figure 6.

4) In the tables showing the water balance, I suggest to differentiate inputs and outputs (perhaps a sign under de header will suffice).

Best regards,

The reviewer

Author Response

We thank the reviewer for providing constructive comments to further improve the quality of the manuscript. Please see below our responses to all comments.

• Done (see Figures 1, 2, 3, and 7).
• Done (see section 3 and pages 8-9).
• Done.
• Done (see captions of tables 5-6).
•  

Author Response File: Author Response.docx

Reviewer 3 Report

Formal comments:

Page 4     …. link to the figure  “(Fig.3 3,D)” should be corrected

Page 6  …. Instead of  “(Shih and Snyder 1984)”  should be “[25]”

Page 7 …  on this page 21 is the author “Nietsch” but on page 22  is “Neitsch”

Page 7 Table 2. …..  “m3/s”  better is “m³/s” … the same is in Table 4.

Page 10 … Figure 4. (should be … panels B and D)

Page 13 ….. “Figure 6.”  should be in bold

Page 16 …  Instead of  “S3= Scenario two”  should be “S3= Scenario three”

Page 19 … for all articles DOI  missing – except “[54]”

Page 20  .. “[27]”and “[28]” … they have the same name and “2016, 8, 182-197”   aren't these the same articles?

Author Response

We thank the reviewer for providing constructive comments aimed to further improve the quality of the manuscript. Below we provided our responses to the comments.

• Corrected (see page 6, lines 137).
• Addressed (see page 9, lines 204).
• Corrected to “Neitsch” (see page 10, line 220)
• Done (see Table 2’s caption).
• Done (see Figures 4 and 5). Please note that the rainfall panels and panels’ names were removed to increase the readability of the figures.
• Done (see Figure 6).
• Corrected (see page 21, line 385).
• Yes, all DOIs are missing because it seems MDPI doesn’t include the DOIs as we have not done the text and bibliography citations manually. We just imported all the citations from google scholar to EndNote X9 and used the MDPI style citation.
• See page 22, lines, 429.
•  

Author Response File: Author Response.docx

Reviewer 4 Report

Special comments: 1) The Figure 1. and Figure 3. are not clear, which need the higher resolution. 2) In the Figure 2., Color is better than pattern for showing a map. 3) How to unify spatial resolution of these data used in SWAT model?. 4) Water balance equation employed in SWAT model is needed in the Methods section. 5) What is the grid size of the HRU, or spatial resolution? 6) In the Table 2., in second and third rows, “0.075 should be 0.75?”. 7) The accurate year on the calibration and the validation needs to be provided in the Figure 4 and Figure 5. 8) In 3.2 section, the first sentence should be “…… an annual average rainfall of 2043mm……”? In addition, what means the sentence “the coastal wetland received 1065 mm for the same period”. 9) In Table 5., streamflow is not equal to sum of runoff, lateral flow and base flow.

Author Response

We thank the reviewer for providing constructive comments aimed to further improve the quality of the manuscript. Below we provided our responses to the comments.

• Done (see Figures 1 & 3). Please note that Figure 3 is more simplified for better readability.
• Addressed (see Figure 2).
• Since SWAT is a semi-distributed model (see section 3, page 8), the model does not use a grid spatial resolution approach to unify the input data into one resolution, but the model internally calculates and groups the different spatial resolution data into a unique combination of land use type, soil type, and slope (calculated from DEM).
• Addressed this by providing a reference that details the water balance equation used in SWAT (see page 8, lines 151-161).
• HRUs are a feature that represent the combination of homogeneous land use, soil, and slope within a sub-basin (see section 3, lines 156-158) and thus doesn’t have a grid size resolution.
• Corrected (see Table 2).
• Inserted (see Figures 4 and 5).
• That sentence is rephrased to avoid the confusion (see page 16, lines 313-316). We wanted to compare the annual average rainfall gradient for over the entire watershed and wetland area, and emphasize on the rainfall variability within the small-scale watershed (see page 16, lines 313-316).
• It is true that the SWAT simulated water yield (generated in the watershed but yet not reach the stream reach to be called streamflow) should not necessarily equal to the sum of runoff, lateral flow, and base flow especially for monthly water balance components due to change in storage, deep aquifer recharge and reach transmission losses. Thus, the term “streamflow” was confusing and we renamed “streamflow” to water yield to avoid confusion (see Table 5) and modified related text (see section 2).
•  

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Reviewers comments addressed.

Author Response

• We thank the Editors and Reviewers for further reviewing and improving the quality of the manuscript. Our responses to all the comments are provided below.

Reviewer #1

Open Review

 

(x) I would not like to sign my review report
( ) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required
( ) Moderate English changes required
(x) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
Is the research design appropriate?	(x)	( )	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	(x)	( )	( )	( )
Are the conclusions supported by the results?	(x)	( )	( )	( )

Comments and Suggestions for Authors

Reviewers comments addressed.

• Thank you!

Author Response File: Author Response.docx

Reviewer 2 Report

Thank you for addressing my comments. I think it is ready for publishing after editorial editing and proofreading.

Best regards and future success.

The reviewer

Author Response

• We thank the Editors and Reviewers for further reviewing and improving the quality of the manuscript. Our responses to all the comments are provided below.

• Reviewer #2

  Open Review

   

  (x) I would not like to sign my review report
  ( ) I would like to sign my review report

  English language and style

  ( ) Extensive editing of English language and style required
  ( ) Moderate English changes required
  (x) English language and style are fine/minor spell check required
  ( ) I don't feel qualified to judge about the English language and style

   

  	Yes	Can be improved	Must be improved	Not applicable
  Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
  Is the research design appropriate?	(x)	( )	( )	( )
  Are the methods adequately described?	(x)	( )	( )	( )
  Are the results clearly presented?	(x)	( )	( )	( )
  Are the conclusions supported by the results?	(x)	( )	( )	( )

  Comments and Suggestions for Authors

  Thank you for addressing my comments. I think it is ready for publishing after editorial editing and proofreading.

  Best regards and future success.

  The reviewer

  • Thank you!

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript has been improved. I suggest publishing it.

Author Response

• We thank the Editors and Reviewers for further reviewing and improving the quality of the manuscript. Our responses to all the comments are provided below.

• Reviewer #3

  Open Review

   

  (x) I would not like to sign my review report
  ( ) I would like to sign my review report

  English language and style

  ( ) Extensive editing of English language and style required
  ( ) Moderate English changes required
  ( ) English language and style are fine/minor spell check required
  (x) I don't feel qualified to judge about the English language and style

   

  	Yes	Can be improved	Must be improved	Not applicable
  Does the introduction provide sufficient background and include all relevant references?	(x)	( )	( )	( )
  Is the research design appropriate?	(x)	( )	( )	( )
  Are the methods adequately described?	(x)	( )	( )	( )
  Are the results clearly presented?	(x)	( )	( )	( )
  Are the conclusions supported by the results?	(x)	( )	( )	( )

  Comments and Suggestions for Authors

  The manuscript has been improved. I suggest publishing it.

  • Thank you.

Author Response File: Author Response.docx

Reviewer 4 Report

Most comments have been replied and corresponding content has been revised in new manuscript. Nevertheless, it needs to polish language expression, such as:

1) Line 169: “SWAT is a user-friendly tool/system…”.

In addition, units of the variables in equations need to be unified, such as:

2) Line 228: in the Equation 2, variables including irr, area_hru, Q_lat,hru have different unit have different units.

Author Response

Reviewer #4 comments

 

• We thank the reviewer for additional comments aimed to further improve the quality of the manuscript. Our responses to the comments are provided below.

Open Review

(x) I would not like to sign my review report 
( ) I would like to sign my review report 

 

English language and style

( ) Extensive editing of English language and style required 
( ) Moderate English changes required 
(x) English language and style are fine/minor spell check required 
( ) I don't feel qualified to judge about the English language and style 

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Is the research design appropriate?	( )	(x)	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	( )	(x)	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

Comments and Suggestions for Authors

Most comments have been replied and corresponding content has been revised in new manuscript. Nevertheless, it needs to polish language expression, such as:

• Line 169: “SWAT is a user-friendly tool/system…”.

 

• Modified (see page 7, line 182). We also thoroughly reviewed and edited the manuscript to address similar issues.

In addition, units of the variables in equations need to be unified, such as:

2) Line 228: in Equation 2, variables including irr, area_hru, Q_lat,hru have different unit have different units.

• While we agree with this comment, we purposely provided different units to the variables used in Equation 2 to be consistent with the SWAT’s input units and equations used in the model. SWAT internally takes care of unit conversion. For example, in Equation 2, 10 is used as a conversion factor to convert mm and ha to m³ and unify it with the unit of irr, which is in m³.

Author Response File: Author Response.docx

Round 3

Reviewer 4 Report

The comments has been replied and revised. Expression is better. However, there are some minor questions in the reversed manuscript, such as:

1)Line 289: In the Figure 4.,  vertical axis is stream flow or current velocity? And current velocity is an instantaneous value, however, horizontal axis is day, vertical axis indicates daily average current velocity? Same to Figure 5.

 

2)Line 313: In the Table 4. the units of the variables is required for better understanding.

 

Author Response

Reviewer #4

 

Open Review

 

(x) I would not like to sign my review report
( ) I would like to sign my review report

English language and style

( ) Extensive editing of English language and style required
( ) Moderate English changes required
( ) English language and style are fine/minor spell check required
(x) I don't feel qualified to judge about the English language and style

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Is the research design appropriate?	( )	(x)	( )	( )
Are the methods adequately described?	(x)	( )	( )	( )
Are the results clearly presented?	(x)	( )	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

Comments and Suggestions for Authors

The comments has been replied and revised. Expression is better. However, there are some minor questions in the reversed manuscript, such as:

• Line 289: In the Figure 4, vertical axis is stream flow or current velocity? And current velocity is an instantaneous value, however, horizontal axis is day, vertical axis indicates daily average current velocity? Same to Figure 5.

 

• The streamflow values in Figures 4 and 5 are already reported with the standard units reported by the SWAT model output, which is cubic meter per second for daily streamflow. However, to clarify this, we modified the y-label’s to “Average daily streamflow” (see Figures 4 & 5 in the revised version)

 

• Line 313: In the Table 4. the units of the variables is required for better understanding.

 

• The units of all values are already reported in Table 4’s caption, but for a better understanding we rephrased the caption (see Table’s caption)

Author Response File: Author Response.docx