Authors have responded reasonably well to all the comments made by two Referees. However, both Referees have expressed their major concern on the presentation quality of the paper and rated it as "Poor"". Referees are also of the opinion that paper needs a major reorganisation before it can be further considered.

Authors are suggested to suitably revise the manuscript by incorporating all the responses in appropriate sections and reorganise the text for further clarity.

Overall, Authors have responded reasonably well to all the comments made by the two Referees. However, “Abstract” is still somewhat confusing and lacks clarity. Authors are suggested to make following changes in the abstract, or as they feel appropriate:

Line 10 should read as: “Isotope data for suspended sediments indicate that POC was mainly derived from ----------.

Line 14, change to: ---- carbon pools are tightly coupled.

Line 14 should read as: Our conservative estimate suggests that 1.17 x 10^10 g of POC is transported to the Three Gorges Reservoir during the study period in 2013.

Line 15 change to: ------ was much lower than large rivers with high abundance of carbonate minerals.

Line 16 should read as: Based on the distribution pattern of POC yield, it is inferred that carbonate minerals (lithology) do not contribute significantly to the riverine POC.

These are some of the suggestions.