Review Reports - Relationships between Wind Effect, Hydrodynamics and Water Level in the World’s Largest Coastal Lagoonal System

Round 1

Reviewer 1 Report

Manuscript Water-599323-V1

Comments to Authors

The paper describes a numerical simulation of water circulation in the Mirim lagoon (Uruguay-Brazil) in relation with the possible future construction of a navigation channel through it and the effects on the natural environment.

More objective information must be provided on the physical system and on the model used. The description of the case is only qualitative and the reader is eventually not able to appreciate if the conclusions are sound or not. Some of the conclusions were already obtained in other papers regarding the near Patos lagoon.

Based on these observations I suggest a major revision of the manuscript.

General comments

Only very few explicit data are provided on the Lagoon and the Channel, Sao Goncalo channel, connecting it to the Patos lagoon and indirectly to the ocean: the extension/surface and bathymetric map of the Lagoon, and the length of the channel. The level statistics at the two extremes, the volume or mean depth at the average level, as mean inflow and outflow should be provided; . The average width and depth of the connection channel would be useful. Sea for instance the paper Moeller O.O. et al., Estuaries Vol. 24(2), 297-311, Apr.2001. Some further information can be obtained from [19].

A (subsurface) dam was constructed in the Channel; nothing is mentioned about the section, barrage closing/opening (if possible) and regulation or emersion, even if it might have prominent effects on water levels.

Regarding the model it is not clear which processes are modelled and which are not. Due to the extension of the lagoon precipitation and evaporation might have relevant effects. Water use for irrigation is mentioned in the paper but not quantified. The Lagoon has a long extension parallel and not far from the coast. Direct seepage to the oceani s apparently not considered even if some authors have analysed it: Niencheski et al. https://doi.org/10.1016/j.marchem.2007.06.004 .

In any case one year is a too short period to obtain results having climatic relevance.

Even if the numerical model should be able to represent stratification effects, no resulti s presented about this subject.

A recent and relevant paper, Costi & al. https://doi.org/10.1016/j.advwatres.2018.05.008, providing information on water level variability in the Lagoon using TELEMAC 2D modelling, is not mentioned notwithstanding similar subject and method.

Detail comments

L.87 Figure 1 is not clear. The area of the Mirim lagoon should be visible and the relative catchment should be indicated.

L.195 The sentence before “thus” does not imply the sentence after “thus”.

L.211 Cancel “be”.

L.213 The two definition of flushing time are not consistent. One is the ratio of average values and the other of instantaneous values. Moreover, since water is practically, the use of mass and volume in the two definitions is just confusing.

L.246 and figure 6 subplot headings. Why slope rather than elevation and elevation difference. Moreover figure 6 does not represent a stationary condition, therefore specify wind intensity and duration or the time coordinate of figure 7.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

Thank you so much for your comments and suggestions to improve our manuscript. The MS is now in better shape than it was the first time around.

Please find below our comments to specific points:

More objective information must be provided on the physical system and on the model used.

Authors: According to your suggestions, the introduction was completely reformulated and now includes more detailed information on the physical system (See Item 1 - Introduction). It is important to mention, however, that information on the surface sediment composition and morphometry will be fully presented elsewhere in the manuscript "Links between surface sediment composition, morphometry and hydrodynamics in a large shallow coastal lagoon", by H.M. Vieira, Jair Weschenfelder, Felipe García-Rodríguez, Elisa Helena Fernandes, Osmar Olinto Möller, which is now almost ready for submission to "Water" soon.

Authors: As suggested, we did include more detailed information on the model used as well. Please see Items 2.1, 2.2 and 2.3.

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The description of the case is only qualitative and the reader is eventually not able to appreciate if the conclusions are sound or not. Some of the conclusions were already obtained in other papers regarding the near Patos lagoon.

Authors: The study case is presented in a logical sequence: the model's performance is evaluated in detail through quantitative calibration and validation exercises (See items 2.4 and 2.5), indicating its ability to study the hydrodynamics of the lagoon based on statistical parameters. Further on, results focused on the quantification of the water level variability calculated by the model for the lagoon and the cumulative river input from the main tributaries (Figure 5) and of the water level difference calculated by the model for the maximum wind conditions (Figure 6). The temporal variability of the relationship between the simulated height difference between the Mirim Lagoon (Figure 7) and the Patos Lagoon (Figure 8) extremities and the wind were also quantified. As this is the first three-dimensional study of the Mirim Lagoon, the surface current velocity distribution throughout the lagoon during maximum wind conditions were also quantified (Figure 9), and from these results the monthly frequency distribution of current velocity in three transects in the Lagoon (Figure 10) was also quantified. Figure 11 presents the very first results of the Mirim Lagoon three-dimensional circulation during maximum wind conditions. Figure 12 presents the estimated contribution of the Mirim Lagoon towards the Patos Lagoon and the quantification of the Flushing time of the lagoon during the simulated period. Based on such results presented in the manuscript, we believe that the case study is not only qualitative but presents novel quantitative information.

Authors: The conclusions of this study were reformulated according to your suggestion, see item 4 - Final Remarks and Conclusions. We believe that the conclusions are now constrained to the novel information introduced in this MS, and can be considered “sound conclusions”.

Authors: Regarding your comment that "the conclusions of this study were already obtained in other studies", we would like to clarify that the majority of published studies on the Mirim Lagoon were included into the manuscript after revision, and they are based on different approaches and objectives, generating preliminary and complementary conclusions to our study. It is also important to mention that this is very first three-dimensional study of this lagoon, bringing new findings to the academic community and towards the sustainable development of the System. We think that all these aspects were also clarified on item 4 - Final Remarks and Conclusions.

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Authors: Please see Lines 40-54 for the area of both lagoons and length of São Gonçalo Channel, and Figure 2B for the Mirim Lagoon bathymetry.

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The level statistics at the two extremes, the volume or mean depth at the average level, as mean inflow and outflow should be provided. The average width and depth of the connection channel would be useful. Sea for instance the paper Moeller O.O. et al., Estuaries Vol. 24(2), 297-311, Apr.2001. Some further information can be obtained from [19].

Authors: We were not sure if the Reviewer referred to the Patos Lagoon or the Mirim Lagoon as Moller et al (2001) actually presents the main features for the Patos Lagoon (i.e., features of the channel connecting the lagoon to the ocean), while Hirata et al (2010) studied the Mirim Lagoon (and the most important features they described are already reported into our manuscript). It is important to emphasize that our study focuses on the Mirim Lagoon hydrodynamics and its contribution towards the Patos Lagoon, and our results highlight: the discharges from the Mirim Lagoon towards the Patos Lagoon ranging from 300 - 2,250 m3/s, with a mean value of 1,100 m3/s; and the Patos Lagoon contribution to the coast during maximum flood is 10,900 m3/s and during maximum ebb is 19,000 m3/s, while the mean flow is 4,500 m3/s.

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Authors: Between Lines 55-71 we did explain that the dam is only closed in periods of low discharge (and consequently low water levels), which happen mainly during summer and autumn. We also clarified that the dam was constructed in a region of the SGC which is 7 m deep and 300 m wide, and that the dam gate is 3.2 m in height and 12 m long, promoting a water level difference of 40 cm.

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Regarding the model it is not clear which processes are modelled and which are not. Due to the extension of the lagoon precipitation and evaporation might have relevant effects. Water use for irrigation is mentioned in the paper but not quantified. The Lagoon has a long extension parallel and not far from the coast. Direct seepage to the ocean is apparently not considered even if some authors have analyzed it: Niencheski et al. https://doi.org/10.1016/j.marchem.2007.06.004 .

Authors: ITEM 2.1 was reformulated as suggested by the Reviewer and presents the main characteristics of the TELEMAC Model, which is a three-dimensional hydrodynamic model based on the usual Navier Stokes Equations. We did not mention the evaporation-precipitation balance because it was not incorporated into the simulation. In this region, precipitation is always predominant, and this would only change in a very extreme La Niña event.

Authors: Regarding the groundwater fluxes between the lagoonal system and the coast, the Reviewer is correct. This process occurs and is investigated at FURG by Prof. Luis Felipe Niencheski, in collaboration with the Skidaway Institute of Oceanography since 2000. However, such specific process is not usually represented in hydrodynamic models for coastal areas. It is normally found in specific groundwater models.

Authors: The amount of water used for irrigation is not monitored or controlled by the environmental agency and local authorities, so this information is not available.

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In any case one year is a too short period to obtain results having climatic relevance.

Authors: Yes, we agree with the Reviewer that a one-year simulation is too short for climatic relevance, but we did not intend to assess the effect of climate on the lagoon. What we did intend to assess was the effect of meteorological (i.e., predominant wind) data on the hydrodynamics. In this sense, a one-year simulation is good enough to gather a data base for a modelling approach. We simulated a 1-year period for which we had a full data set to force the model, and also that represented a period of high discharges and typical winds.

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Even if the numerical model should be able to represent stratification effects, no result is presented about this subject.

Authors: Yes, with this three-dimensional model we are able to represent stratification very well, but as the study was focused on the Mirim Lagoon and the dam prevents the entrance of salty water in this system, stratification was not mentioned. We were able, however, to evaluate the bidirectional flows observed in some regions of the Mirim Lagoon, which is an absolutely new information (see Fig. 11).

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Authors: Excellent suggestion. This paper was incorporated into the introduction and discussions of our results, as requested.

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L.87 Figure 1 is not clear. The area of the Mirim lagoon should be visible and the relative catchment should be indicated.

Authors: The purpose of Figure 1 is to give a general idea about the system (Mirim Lagoon + Patos Lagoon), the main Mirim Lagoon tributaries, and the existence of the Mercosul Waterway. More details about the Mirim Lagoon bathymetry are presented in Fig. 2B.

The Mirim Lagoon catchment area was already described in previous studies, such as the ones presented below. In order to clarify this point for the Reviewer, we are sending a complementary figure to illustrate.

Vieira, E. F., Rangel, S. R. S. ‘Rio Grande do Sul: Geografia Física e Vegetação’. Porto Alegre, Editorial Sagra. 1984.

Vieira, E. F., Rangel, S. R. S. ‘Planície Costeira do Rio Grande do Sul: Geografia Física, Vegetação e dinâmica sócio-demográfica’. Porto Alegre, Editorial Sagra. 1988.

Gouvêa, T., Zarnot, D. H., Alba, J. M. F.Caracterização geoambiental e histórica do processo de desenvolvimento da bacia da Lagoa Mirim. In: Sustentabilidade Socioambiental da Bacia da Lagoa Mirim. Embrapa Clima Temperado. Pelotas, RS. (1):19-30. 2010.

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L.195 The sentence before “thus” does not imply the sentence after “thus”.

Authors: The sentence was reformulated

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L.211 Cancel “be”.

Authors: The sentence was reformulated

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Authors: The Reviewer is correct. In order to clarify this, we removed the first definition and kept the second, which is the one effectively used in this work.

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Authors: The text was corrected accordingly (See Line 624). Figure 6 heading were removed. This Figure represents the moments of maximum SW and NE winds during the simulation, where the wind intensity was 12 and 10 m/s, respectively.

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Regarding the overall comments, we can highlight that:

The Engligh grammar was fully revised in the manuscript, as requested.

Methods description was substantially improved according to suggestions from all Reviewers.

The quality of the figures was substantially improved, according to suggestions.

Conclusions were fully reformulated, as requested.

Author Response File: Author Response.docx

Reviewer 2 Report

Relationships between wind effect, hydrodynamics and water level in the world's largest coastal lagoonal system

By H. A. Oliveira1; E.H. Fernandes, O.O. Möller and F. García-Rodríguez

The paper illustrates the results of a numerical study of the hydrodynamics of the Mirim Lagoon, located in the Southern Brazil and eastern Uruguay.

The paper is interesting since it provides new information on the flow inside the lagoon which could be useful for the planning and implementing of a waterway.

The language is generally correct.

Recent works on the hydrodynamic of Patos-Mirim lagoon and other important lagoons should be cited in the introduction. See for example: Martelo, A. F., Trombetta, T. B., Lopes, B. V., Marques, W. C., & Möller, O. O. (2019). Impacts of dredging on the hydromorphodynamics of the patos lagoon estuary, southern brazil. Ocean Engineering, 188 doi:10.1016/j.oceaneng.2019.106325 Costi, J., Marques, W. C., Paula Kirinus, E. D., Freitas Duarte, R. D., & Arigony-Neto, J. (2018). Water level variability of the mirim - são gonçalo system, a large, subtropical, semi-enclosed coastal complex.Advances in Water Resources, 117, 75-86. doi:10.1016/j.advwatres.2018.05.008 Montaño-Ley, Y., & Soto-Jiménez, M. F. (2019). A numerical investigation of the influence time distribution in a shallow coastal lagoon environment of the gulf of california.Environmental Fluid Mechanics, 19(1), 137-155. doi:10.1007/s10652-018-9619-3 Cavallaro, L., Iuppa, C., & Foti, E. (2017). Effect of partial use of Venice flood barriers.Journal of Marine Science and Engineering, 5(4) doi:10.3390/jmse5040058 Mel, R., Carniello, L., & D'Alpaos, L. (2019). Addressing the effect of the mo.S.E. barriers closure on wind setup within the venice lagoon. Estuarine, Coastal and Shelf Science, 225 doi:10.1016/j.ecss.2019.106249 Colvin, J., Lazarus, S., Splitt, M., Weaver, R., & Taeb, P. (2018). Wind driven setup in east central florida's indian river lagoon: Forcings and pameterizations.Estuarine, Coastal and Shelf Science, 213, 40-48. doi:10.1016/j.ecss.2018.08.004 33 Please specify the object of the implementation Section 3.1 Please give more information about the numerical model. I assume that the author adopted TELEMAC in 3D configuration. Did you adopt the “Hydrostatic” ore the “Non-hydrostatic” mode? Did you adopt a turbulence model? Section 3.2 The paper is focused on the hydrodynamic of the Mirim Lagoon, which is disconnected from the Patos Lagoon by a dam constructed in the Sao Goncalo Channel. Why did you analyse the entire domain described in Figure 2? The mesh resolution in the subdomain should be detailed. Give some information on the vertical resolution of the model. 145 How did you interpolated the data? 210 Please define “sigma levels” 220-222 Please remove. It is a repetition of the previous sentence. Figure 7 Improve the image. The letter A, B and C are not visible. The label of the x-axis in subfigure C is not visible. Figure 8 Improve the image. The letter A, B and C are not visible. The label of the x-axis in subfigure C is not visible. 318-323 Please insert a picture to identify these areas 420 Please Correct “bserved” with “Observed”

Author Response

Dear Reviewer,

Thank you so much for your comments and suggestions to improve our manuscript.

Please find below our comments to specific points:

Recent works on the hydrodynamic of Patos-Mirim lagoon and other important lagoons should be cited in the introduction. Examples provided.

Authors: Excellent suggestions. The recommended manuscripts were included in the introduction and discussion whenever appropriate.

33 Please specify the object of the implementation Section 3.1

Authors: The Section Title was corrected accordingly.

Please give more information about the numerical model. I assume that the author adopted TELEMAC in 3D configuration. Did you adopt the “Hydrostatic” ore the “Non-hydrostatic” mode? Did you adopt a turbulence model?

Authors: We updated information about the TELEMAC model as requested and they are part of the 2.1 TELEMAC Model Section. Lines 297-318.

Section 3.2 The paper is focused on the hydrodynamic of the Mirim Lagoon, which is disconnected from the Patos Lagoon by a dam constructed in the Sao Goncalo Channel. Why did you analyse the entire domain described in Figure 2?

Authors:The Mirim Lagoon is connected to the Patos Lagoon through the São Gonçalo Channel. The dam construction limited the entrance of salt water from the Patos Lagoon, but the fluxes from the Mirim Lagoon towards the Patos Lagoon do exist and are very important.

The mesh resolution in the subdomain should be detailed.

Authors: details included in Section 2.2 Numerical Domain, Lines 323-325

Give some information on the vertical resolution of the model.

Authors: details included in Section 2.2 Numerical Domain, Line 321, including a traditional reference on the subject.

145 How did you interpolated the data?

Authors: details included in Section 2.3 initial and Boundary Conditions, Lines 341 and 342.

210 Please define “sigma levels”

Authors: details included in Section 2.2 Numerical Domain, Line 321, including a traditional reference on the subject.

220-222 Please remove. It is a repetition of the previous sentence.

Authors: These Lines appear in the 3.7 Flushing Time Section and do not look like a repetition of the previous sentence. Please be more specific and we will be happy to correct.

Figure 7 Improve the image. The letter A, B and C are not visible. The label of the x-axis in subfigure C is not visible. Figure 8 Improve the image. The letter A, B and C are not visible. The label of the x-axis in subfigure C is not visible.

Authors: Figures were improved.

318-323 Please insert a picture to identify these areas

Authors: The identification of these areas was included in Figure 2, as requested.

420 Please Correct “bserved” with “Observed”

Authors: Done

Regarding the overall comments, we can highlight that:

The Engligh language was fully revised in the manuscript, as requested. Introduction was completely reformulated according to suggestions and including new references. Methods description was substantially improved according to suggestions. The quality of the figures was substantially improved, according to suggestions. It is not possible, however, to modify the research design at this stage, but we consider it adequate for the manuscript objectives. We also consider Conclusions supported by the Results

Reviewer 3 Report

This manuscript addresses the interesting and important topic of relationships between wind, hydrodynamics and water level in Mirim Lagoon. Although I don't have local knowledge of this coastal system, I think this work would be of interest to those seeking to understand coastal lagoon's dynamics and its impacts on navigation conditions and development. The authors discuss thoroughly using numerical modeling approach about the Mirim Lagoon hydrodynamic response to the main physical forcing, i.e., wind and freshwater discharge. I don't have major concerns in the methodology, but I'd suggest the authors to consider the following revisions and improve figures' quality and formatting to meet the standard of this journal. 1. Combine Section 1 and 2 to be Introduction. 2. Line 108: "extra-large" is a bit vague in this statement. 3. Line 111: "it" to "its". 4. Line 111: "modelled" to "model". 5. Line 125: "non-structured" to "unstructured". 6. Line 127-128: Clarify the statement about increasing model efficiency. 7. Line 138: Is constant water level initial condition justified in this domain? What does astronomical tide look like in this region? 8. Line 159: Caption missing (D). 9. Line 161: "The model ability" to "The model's ability". 10. Line 201: Could higher-resolution ECMWF wind fields be used? 11. Is there any observed wind data that you can use to compare with ECMWF? 12. Line 208: this 3.6 section only contains 2 sentences. It seems not necessary to be a separate section. 13. Figure 7 and Figure 8: it'd be better to improve the axis titles and axis labels as some of them are not clear to read. 14. Line 275: "are" to "is". 15. Figure 9: Can you make each panel consistent with each other in terms of the size? 16. Figure 10: Improve figure quality as A and C are not shown clearly. 17. Line 438: "Sharp" to "Steep". 18. Can you reorder references list to be in proper order?

Author Response

Dear Reviewer,

Thank you so much for your comments and suggestions to improve our manuscript.

Please find below our comments to specific points:

Combine Section 1 and 2 to be Introduction.

Authors: Excellent suggestion. Introduction was corrected accordingly.

Line 108: "extra-large" is a bit vague in this statement.

Authors: We agree. The expression "extra" was removed from the text.

Line 111: "it" to "its".