Dear Authors,

After receiving two reviews we would like to consider this manuscript after major revisions. In particular we would like the authors to respond as they have in their discussion to the issues related to reporting of temporal dynamics. This is viewed as an important component that needs clarification. The outlined approach by the authors looks well planned. Furthermore, the authors provide a strong response to reviewer 1 regarding the role that hydrology may or may not play. It is suggested that key points of the discussion provided in the reviewer response be added to the manuscript. Finally, it would be appreciated if the authors clearly acknowledge the attention being giving to methane dynamics in reservoirs, and put their estimate of CO2 into context with the methane literature. This editor believes that the discussion would be strengthened.

Regarding the response to reviewer 2 - this editor believes that most of the concerns raised by this review can be handled with additional descriptions added to the text. It is appreciated that reviewer 2 raised concern regarding the level of details provided in the initial discussion manuscript. However, most of these issues can be further handled with additional citations to methods, and protocols by the specific equipment manufacturers. Please ensure that any company (example YSI) includes the proper manufacturer name and location. Finally, a point raised by reviewer two regarding the appropriateness of using calculated CO2 values is well handled by the author response. If these systems show pH values >7, there is significantly less concern regarding the influence of organic acids on the titration for alkalinity.

Overall, the response to the reviews looks appropriate and well planned. We look forward to a re-submission of this article.

Dear Authors,

It appears that you have adequately handled nearly all of the reviewer comments. In addition, I have highlighted some additional comments below that should be addressed. It is also recommended that the authors spend time addressing grammatical errors, while paying attention to the use of plurals, formatting and spacing, as well as tense and check all superscripts, subscripts and figure/axis labels.

Specific comments are below:

In section 3.4 - please consider rewriting this. The wording is very difficult to understand. Lines 5-10 suggest significant differences between day and night flux, but then lines 15-20 you suggest that the difference is not statistically significant. Furthermore - lines 18-25 you suggest that pH didn't vary - but with any observed change in CO2 you see a change in pH. In some cases a 0.3 unit change in pH can results in a large shift in carbonate equilibrium. Can you make it clear here that at a pH of 8.2 this will not alter the CO2 significantly?

Figures 3&4&7. please ensure that each figure can stand on its own. Therefore please add all needed information to interpret the figure to the figure legend, for example - the IQR, box ranges, squares etc to both figure legends.

Please try not to cover figures with labels or legends.

Figure 9: can you provide reasoning why your are using a non-linear fit for the riverine inlet vs. a linear fit for the outlet in this comparison? what is this justified?

Table 1: Please clarify the table legend or table, right now the data are suggested to be means in the legend, but are being called Med(min-max) in the table. Are they medians or means?

We look forward to a revised version of the manuscript.

Dear Authors, This manuscripts appears to have addressed all major concerns identified throughout the review process. There remain some additional technical issues that should be addressed.

Units - starting in the abstract - are the flux units of Carbon or CO2 - consider a unit like mg-C m-2 yr-1, or use a molar unit but be consistent throughout.

Figure 7 . change incontinuous to discontinuous to match figure legend.

pg 1 Line 18 - check grammar - pelagic area...resulted from (please check grammar
throughout).

pg 3 line 19 - how many dams in china? can you state?