the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Impacts of anthropogenic water regulation on global riverine dissolved organic carbon transport
Yanbin You
Binghao Jia
Yan Wang
Longhuan Wang
Ruichao Li
Heng Yan
Yuhang Tian
Si Chen
Abstract. Anthropogenic water regulation activities, including reservoir interception, surface water withdrawal, and groundwater extraction, alter riverine hydrologic processes and affect dissolved organic carbon (DOC) export from land to rivers and oceans. In this study, schemes describing soil DOC leaching, riverine DOC transport, and anthropogenic water regulation were developed and incorporated into the Community Land Model 5.0 (CLM 5.0) and the River Transport Model (RTM). Three simulations by the developed model were conducted on a global scale from 1981 to 2013 to investigate the impacts of anthropogenic water regulation on riverine DOC transport. The validation results showed that DOC exports simulated by the developed model were in good agreement with global river observations. The simulations showed that DOC transport in most rivers was mainly influenced by reservoir interception and surface water withdrawal, especially in central North America and eastern China. Four major rivers, including the Danube, Yangtze, Mississippi, and Ganges Rivers, have experienced reduced riverine DOC flows due to intense water management, with the largest effect occurring in winter and early spring. In the Danube and Yangtze River basins, the impact in 2013 was four to five times greater than in 1981, with a retention efficiency of over 50 %. The Ob River basin was almost unaffected. The total impact of anthropogenic water regulation reduced global annual riverine DOC exports to the ocean by approximately 13.36 Tg C yr−1, and this effect increased from 4.83 % to 6.20 % during 1981–2013, particularly in the Pacific and Atlantic Oceans.
Yanbin You et al.
Status: open (until 18 Apr 2023)
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RC1: 'Comment on esd-2023-2', Anonymous Referee #1, 20 Mar 2023
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This manuscript incorporated a riverine dissolved organic carbon transport scheme to the land surface model CLM5.0 to evaluate the impacts of anthropogenic water regulation on riverine DOC discharges and transport. The paper is well written, presenting an interesting work in a clear and organized way. I have a few minor comments below.
- Equation (2): Please denote the unit of DOC leaching flux.
- Line 176: “Riverine DOC is mainly derived from organic carbon leaching processes in soil”; some literature support is required here.
- Line 189-190: where is the reference for choosing this weighting coefficient?
- Section 3.1: I suggest adding a table to show the main datasets used for model running and validation in this study.
- Line 221: Please introduce the details for the human water use activity dataset. A description of what data sources were used?
- Line 205: Only the fluxes into the soil carbon pool after surface water extraction are described. What about groundwater extraction?
- In Section 2.1, the parameters mentioned in the developed soil and river carbon dynamics parameterization scheme are uniform or spatially varying?
- Line 252: Figures 3a and 3c seem to underestimate. Please check carefully and modify.
- Line 273: Are constants (0.3 and 0.7) in equations the same for the whole world?
- This study developed a model to describe the soil carbon leaching and riverine carbon transport processes, which are not well described in previous land surface models. But the discussion of current uncertainties and limitations in modeling is missing. It should be discussed more.
- Line 354-355: The authors state that the three rivers were affected by minor groundwater regulation. Please briefly explain the impact and the reasons.
- In section 5, some words about future work are needed.
Citation: https://doi.org/10.5194/esd-2023-2-RC1 -
RC2: 'Comment on esd-2023-2', Anonymous Referee #2, 20 Mar 2023
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This study aims to assess the effects of anthropogenic regulation of waters on the global transport of DOC by rivers. Given the importance of DOC in the carbon cycle and the potential of human activities to alter its cycling, this is a very important aim. I find the paper generally interesting, but have a few concerns:
The presentation can be made clearer. The authors should make an effort to make it more accessible to non-modelers (like me), and to readers who want to take home the message without detailed reading of the methods. For example, the different simulations of control conditions and different parts of water regulation considered (CTL, EXPA, EXPB) are in several of the figures presented without explanation or spelling out.
Is there some way to add (or more carefully discuss) uncertainty ranges around the various estimates and graphs? The current version presents and compares several numbers with 3-4 significant digits, with no confidence intervals.
Table 2 could be expanded, it appears incomplete. There are several additional estimates of DOC export (possible resulting in a higher median than presented in the manuscript). Some (but not all) are cited in Drake et al. 2018 (Limnol Oceanogr Letters).
I do not understand how transformations in the regulated and unregulated waters are treated. The methods (line 196) say that “migration transformation” is ignored in the model, and loss rate is assumed equal in reservoirs and rivers. In contrast, one of the model results (line 287) is suggested to be due to increased residence time by the construction of reservoirs, causing increased DOC removal. How is this compatible?
Line 292: “alpine” should be “arctic”
Citation: https://doi.org/10.5194/esd-2023-2-RC2
Yanbin You et al.
Yanbin You et al.
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