Water and Sediment Budget of Casiquiare Channel Linking Orinoco and Amazon Catchments, Venezuela†
Round 1
Reviewer 1 Report
In their study, entitled "Water and sediment budget of Casiquiare channel linking Orinoco and Amazon catchtments, Venezuela", the Authors describe in detail the hydrological characteristics of the Casiquiare River, a ‘chameleon’ channel that diverts water and sediment from the Orinoco headwaters towards the Rio Negro and the Amazon River.
The article illuminates the quite peculiar and extremely fascinating topic of ambiguous drainage divide between the two largest rivers in South America, and is a pleasure to read. Such an ongoing river capture may have an analogue in the Selinda spillway of southern Africa, which diverts waters from the Okavango towards the Rivers Cuando and Zambezi. Although there are significant differences between the two cases, the Authors might choose to draw a brief comparison between these two cases.
The article is very well conceived and undoubtedly merits publication after minor revision. As a critical contribute which may help in the revision process, I found section 4 a bit awkward to read. Language expressions may be made clearer, and misspellings amended (e.g., Cunucuma versus Cunucunuma). Also, Figure 5 would be easier to read if a kilometric scale is added, and I was unable to spot Quiritari Island in any of the six panels.
In the end, I can only make my sincere compliments to the Authors to have enlightened a very significant aspect of the drainage system of South America, and thank the Editor for having given me the opportunity to review this very interesting manuscript, which I will be waiting to see published soon.
Faithfully yours,
Eduardo Garzanti Milano, 7th September 2019
Comments for author File: 
Comments.docx
Author Response
Response to Reviewer 1 Comments
We thank the reviewer for his comments which are discussed in the following paragraphs.
Point 1: English language and style are fine/minor spell check required.
Response 1: Small grammatical errors have been corrected and a native English speaker reviewed the paper to improve aspects of styles.
Point 2: In their study, entitled "Water and sediment budget of Casiquiare channel linking Orinoco and Amazon catchments, Venezuela", the Authors describe in detail the hydrological characteristics of the Casiquiare River, a ‘chameleon’ channel that diverts water and sediment from the Orinoco headwaters towards the Rio Negro and the Amazon River. The article illuminates the quite peculiar and extremely fascinating topic of ambiguous drainage divide between the two largest rivers in South America, and is a pleasure to read. Such an ongoing river capture may have an analogue in the Selinda spillway of southern Africa, which diverts waters from the Okavango towards the Rivers Cuando and Zambezi. Although there are significant differences between the two cases, the Authors might choose to draw a brief comparison between these two cases.
Response 2: The Casiquiare Channel is unique in the sense that joins the basins of two of the largest rivers in the world. However, we consider pertinent the suggestion of the reviewer and a new section was added (Section 9) to illustrate other river captures abroad.
Point 3: The article is very well conceived and undoubtedly merits publication after minor revision. As a critical contribute which may help in the revision process, I found section 4 a bit awkward to read. Language expressions may be made clearer, and misspellings amended (e.g., Cunucuma versus Cunucunuma). Also, Figure 5 would be easier to read if a kilometric scale is added, and I was unable to spot Quiritari Island in any of the six panels.
In the end, I can only make my sincere compliments to the Authors to have enlightened a very significant aspect of the drainage system of South America, and thank the Editor for having given me the opportunity to review this very interesting manuscript, which I will be waiting to see published soon.
Response 3: We agree with the reviewer opinion that Section 4 is awkward to read, but we could not find a better way to explain the time evolution of the Casiquiare Channel. However, spelling errors were corrected (e.g. Cunucuma versus Cunucunuma) and a graphical scale was incorporated into Figure 5 for ease of reading, as well as the location of features on panels such as the island of Quiritari.
Author Response File: Author Response.docx
Reviewer 2 Report
This paper aimed to review water and sediment budget of Casiquiare river in Venezuela in the Amazon basin. However, there is a major flaw in structuring the paper and presenting the information. The manuscript needs major revision before it could be considered for publication. Some key points are noted here:
Too much on physical description of the river and very less information on ‘Water and Sediment budget’ which is very contrary to the title of the paper Introduction section should describe why water and sediment budget is important for the region and globally, followed by how researchers quantified water and sediment budget in the past in general and in particular for the study region. Section 2 ‘DISCOVERY OF THE CASIQUIARE CHANNEL’ doesn’t carry any useful information and can be deleted entirely. Section 3 ‘GENERAL DESCRIPTION’ Once again heavily focused on physical description of the river. Section 4 ‘ORIGIN AND EVOLUTION OF THE CASIQUIARE CHANNEL’ – No new information in this section. Major proportion could be deleted without losing any merit. Section 5: ‘DATA AND METHODOLOGY’ this section is more relevant for a research article not for a review article.I recommend resubmitting this manuscript as a Research Article with additional analysis on water and sediment budget.
Author Response
Response to Reviewer 2 Comments
We thank the reviewer for his comments which are discussed in the following paragraphs.
Reviewer Comment: This paper aimed to review water and sediment budget of Casiquiare river in Venezuela in the Amazon basin. However, there is a major flaw in structuring the paper and presenting the information. The manuscript needs major revision before it could be considered for publication. Some key points are noted here:
Point 1: Too much on physical description of the river and very less information on ‘Water and Sediment budget’ which is very contrary to the title of the paper Introduction section should describe why water and sediment budget is important for the region and globally, followed by how researchers quantified water and sediment budget in the past in general and in particular for the study region.
Response 1: Very few investigations have been carried out in the Casiquiare channel. It is important for the authors to show a complete physical description of this hydrological singularity considered to be unique in the world given the magnitude of the joining basins and its geomorphological, hydrological and geochemical characteristics. The last important fieldwork in the Casiquiare channel was conducted by some of the authors in 2000 during the 'Humboldt-Amazonia 2000' expedition. Here a hydrosedimentary and geochemical survey was carried out both at the Orinoco bifurcation and at the confluence with the Guainia River towards the Negro River. These measurements are unique given that since several decades, this sector has been affected by the presence of paramilitary forces and drug trafficking that control the area. Previous studies made by other researchers (U.S. Army Corps of Engineers, 1943, and Pérez, 2002) were interested more in the hydrology and hydraulics of the system, than in the sediment balance. Water and sediment budget is important in the Casiquiare system because of future plans for establishing a South American river integration system through the Orinoco, Casiquiare, Negro, Amazon, Paraguay, Parana and Río de la Plata Rivers (CAF, 1998).
The last two paragraphs were incorporated in the text of the paper (Section 10) to stress the importance of this study.
Point 2: Section 2 ‘DISCOVERY OF THE CASIQUIARE CHANNEL’ doesn’t carry any useful information and can be deleted entirely. Section 3 ‘GENERAL DESCRIPTION’ Once again heavily focused on physical description of the river. Section 4 ‘ORIGIN AND EVOLUTION OF THE CASIQUIARE CHANNEL’ – No new information in this section. Major proportion could be deleted without losing any merit.
Response 2: We consider the development of these sections in the manuscript to be of great value for the purpose of the research, which is to establish an appropriate frame of reference before introducing the new data and methodology in the paper. Additionally, we believe that it helps for a better understanding of readers, as has been commented by Reviewer Number 1.
Point 3: Section 5: ‘DATA AND METHODOLOGY’ this section is more relevant for a research article not for a review article. I recommend resubmitting this manuscript as a Research Article with additional analysis on water and sediment budget.
Response 3: We believe that our paper is a research article that has a literature and background review part, just as a serious research work should have.
References
CAF (1998). Los Ríos nos unen. Integración fluvial suramericana, 244 p, Corporación Andina de Fomento. Caracas.
Pérez H., D. (2002). Mediciones hidrológicas en el sector alto Orinoco – caño Casiquiare. Estados Amazonas. Caracas MARNR, febrero, 9 p. + annexes.
USACE (U.S. Army Corps of Engineers). (1943). Orinoco-Casiquiare-Negro Waterway. Venezuela-Colombia-Brasil, USA, 3 vol.
Author Response File: Author Response.docx
