the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Can the combining of wetlands with reservoir operation largely reduce the risk of future flood and droughts?
Yanfeng Wu
Jingxuan Sun
Boting Hu
Y. Jun Xu
Alain N. Rousseau
Abstract. Wetlands and reservoirs are important water flow and storage regulators in a river basin; therefore, they can play a crucial role in mitigating flood and hydrological drought risks. Despite the advancement of river basin theory and modeling, our knowledge is still limited about the extent that these two regulators could have in performing such a role, especially under future climate extremes. To improve our understanding, we first developed a framework coupling wetlands and reservoir operations with a semi-spatially explicit hydrological model and then applied it in a case study involving a large river basin in Northeast China. The projection of future floods and hydrological droughts was performed using this framework during different periods (near-future: 2026–2050, mid-century: 2051–2075, and end-century: 2076–2100) under five future climate change scenarios. We found that the risk of future floods and hydrological droughts can vary across different periods, in particular, will experience relatively large increases and slight decreases. This large river basin will experience longer duration, larger peak flows and volume, and enhanced flashiness flood events than the historical period. Simultaneously, the hydrological droughts will be much more frequent with longer duration and more serious deficit. Therefore, the risk of floods and droughts will overall increase further under future climate change even under the combined influence of reservoirs and wetlands. These findings highlight the hydrological regulation function of wetlands and reservoirs and attest that the combining of wetlands with reservoir operation cannot fully eliminate the increasing future flood and drought risks. To improve a river basin’s resilience to the risks under future climate change, we argue that implementation of wetland restoration and development of accurate forecasting systems for effective reservoir operation are of great importance. Furthermore, this study demonstrated a wetland-reservoir integrated modeling and assessment framework that is conducive to risk assessment of floods and hydrological droughts, which can be used for other river basins in the world.
Yanfeng Wu et al.
Status: final response (author comments only)
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RC1: 'Comment on egusphere-2022-1103', Anonymous Referee #1, 03 Dec 2022
“Can the combining of wetlands with reservoir operation largely reduce the risk of future flood and droughts?” presents an original study aiming at discussing whether the combining of wetlands with reservoir operation can largely reduce the risk of future floods and droughts in the Nenjiang River Basin. The data of this paper is very comprehensive and the method is reasonable. The results are helpful for understanding the role of wetlands and reservoir operation in mitigating basin hydrological risks under climate change, which make this manuscript worth publishing. I recommend to accept this manuscript after minor revisions to address following general and specific comments.
General comments:
- Hydrological model is an important tool to understand wetland hydrological functions, and the same is true for observations. This cannot be neglected in research progress and discussion.
- I understand that wetland and reservoir can be regarded as green and gray Infrastructure strategy respectively. The authors showed that the combination of them can experience the risks of hydrologic failure under future climate change. This is an interesting and important finding that can be further discussed beyond the current content.
- For different sub-periods under the constraints of three SSPs, the projected results are somewhat different, no matter floods and droughts, which can come into being some uncertainties and should be discussed.
- The assumption about without wetland scenarios, i.e., “wetland areas are not removed, but they are treated as the land cover of saturated soils”. How the regulation function is not accounted for? I think there may be uncertainty here.
- Minor errors andinadequacies in details that need to be double-check and revised. See specific comments below.
Specific comments:
Line 40 and 718. Diffenbaugh et al., 2015a and Diffenbaugh et al., 2015b are the same paper.
Lines 42-43. Please cite the references in the main text correctly. Move “Güneralp et al., 2015” to the end of the sentence.
Lines 45-46. Suggest to say global scale first and then regional scale.
Line 64. Inert “However” before unlike.
Line 132. Delete “and storage”.
Line 137. Insert then after “We”.
Line 146. Insert hydrological after “future”.
Line 158-159. Three wetlands of international importance do not represent much. Please rewrite.
Line 160. What’s the contributing drainage areas of wetlands?
Line 163-164. Songnun Plain or Songnen Plain? Please be consistent with Figure 1.
Line 168. Revise “significantly” to largely.
Line 228-229. What are the two wetland modules. Please specify here.
Line 231. The reference format is incorrect.
Line 242. I still haven't seen a definition of contributing areas here.
Line 257. Kinematic wave equation, loss reference here.
Line 274. What is the time-step length in this study?
Lines 272-274, 277-279. Loss of units for formular parameters.
Citation: https://doi.org/10.5194/egusphere-2022-1103-RC1 -
AC1: 'Reply on RC1', Guangxin Zhang, 05 Jan 2023
Publisher’s note: this comment is a copy of AC4 and its content was therefore removed.
Citation: https://doi.org/10.5194/egusphere-2022-1103-AC1 - AC4: 'Reply on RC1', Guangxin Zhang, 19 Feb 2023
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RC2: 'Comment on egusphere-2022-1103', Anonymous Referee #2, 27 Dec 2022
The authors developed a method for integrating wetlands and reservoirs into a semi-spatially explicit modeling framework (PHYSITEL/HYDROTEL) to project the magnitude, duration, and frequency of future floods and droughts in a northeast China river basin.
This is a straightforward paper that will be a great contribution toward our scientific understanding of how wetlands and reservoirs mediate droughts and floods, as part of the push for nature-based solutions. It also emphasizes the importance of integrating wetland and reservoir hydrological processes into watershed-scale models for large river basins.
Two main points for the authors to consider:
- The authors need to recheck the results text and compare that to their figures. The statements in the text often do not correspond to the figures – particularly those discussion future flood risks. Please see my specific comments below. Also, some figures (e.g., Figure 6) are not labeled, which makes it difficult to following along with some of the results.
- The paper is generally well-written, but please re-review it for grammatical errors. I made a few specific suggestions below, but there are several others throughout.
I also have some general suggestions, including:
Line 43 – Delete “In the future” to make verb tenses correct.
Line 46 – Move “disaster-related” to before the word “loss”.
Line 107 – Change to “included”, not “including”.
Lines 107-112 – Not 100% following this statement: As I read it, it states that integrating wetland and reservoir hydrological processes in the calibration process increases model error and uncertainties but that integrating wetlands and reservoirs (without processes?) minimizes uncertainties and improved model performance? The studies cited *do* integrate some hydrological processes of wetlands and reservoirs, and overall these statements do not seem to align. Could you please clarify this statement?
Figure 1. The caption says the figure shows elevation, isolated wetlands, riparian wetlands, their drainage areas, and land-use types. Out of these listed, I only see lumped “wetlands” and nothing else in the figure legend indicating the other listed characteristics of the watershed. Please amend the figure or the caption.
Lines 240-241: Are only the pixels adjacent to the hydrographic network considered riparian and all others are isolated? Please include that information here. Also, in the subsequent lines, you may want to define for the reader what the HEW concept is and to specifically mention the “lumped” nature of HEWs. Just a few extra words are needed here for clarity.
Lines 256-261: Within the RHHU, isolated wetlands cannot hydrologically connect to RWs, correct, because of spatial lumping? May be worth mentioning here.
Lines 301-302: What did you do with the data once overlaid? Did the 2015 wetland distribution maps trump the land-use/land-cover data (meaning did you use that instead)? Please mention here how the wetlands were represented once the overlay with the lu-lc data happened.
Lines 320-322: So to be clear, you have two calibrated models: one with wetlands and one without? I read later (lines 367-369) that the wetland- and reservoir-integrated model is used for future flow projections. I would mention that here, too, since it’s not clear here why there were two model calibrations.
Line 340: Had you considered using a behavioral parameter set so that output uncertainty bounds could be produced?
Line 349: Why use the NSE here when in lines 340-342 you argued against it? Please add the rational here.
Line 351: Add “be” in front of unreliable.
Line 498: Replace “Specially” with “In fact”.
Line 565: Add “and” in front of “increase”
Paragraph starting on 559 – It would be helpful to point to the exact figure (e.g., Figure 4b or Figure 5d) when describing results so that the reader can follow along closely with the text. It will also help to correct some of the errors listed below.
Lines 566-568: The near-future flood volumes appear to remain the same for the near future SP126 and SP370 pathways in Figure 4g and do not decrease in Figure 5c = the statement and figures do not seem to correspond. Also, what does varying contrarily mean? Check these statements and please clarify. Similarly...
Lines 568-569: Flashiness does *not* appear to follow the trends stated in the text, compared to Figure 5d. Flashiness also doesn’t increase substantially for SSP370, as stated in the text, in the near future. It decreases in Figure 5d. Also, near-century needs to be changed to near future on Line 569.
Check sentence on line 571-572 – “...flashiness will experience a considerable increase of flashiness...”???
Figure 6: The SSPs are not labeled (I *think* the columns represent SSPs?), so it’s difficult to interpret Figure 6. Please re-do the figure with labels and check/re-write, if necessary, the paragraph from 584-596 and the one from 603-612 to correspond with Figure 6.
Lined 615: Add “d” to increase.
Line 619: Delete “y” from clearly and add “be” in front of equivalent.
Line 625: Change “shorting” to “shortening”.
Line 627: capitalize SSP in ssp126.
Figure 9: SSPs need to be labeled on the figure itself.
Lines 627-629: Definitely true, though that is unclear in the violin plots (Figure 7). I would suggest considering moving Figure 7 and Figure 4 to the supplemental. They don’t really add much and can partially confuse the story because the results are visually clear at that resolution.
Lines 847-878: It seems the study explored how the integration of wetlands and reservoirs affect the streamflow test statistics for a river basin modeling framework and how climate-change induced floods and droughts can be projected using this wetland- and reservoir- integrated model. That’s slightly more nuanced than what is currently stated and seems a bit more correct?
Citation: https://doi.org/10.5194/egusphere-2022-1103-RC2 -
AC2: 'Reply on RC2', Guangxin Zhang, 05 Jan 2023
Publisher’s note: this comment is a copy of AC5 and its content was therefore removed.
Citation: https://doi.org/10.5194/egusphere-2022-1103-AC2 -
AC5: 'Reply on RC2', Guangxin Zhang, 19 Feb 2023
We would like to sincerely thank the reviewer#2 for taking time to review our manuscript. We greatly appreciate your comments and suggestions, all of which are very helpful to improve the readability of our manuscript. We completely agree with the reviewer's suggestions and have diligently revised the manuscript. Please see the attached document for point-to-point responses. Note that please see the peer-to-peer responses we uploaded this time because we made some changes.
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RC3: 'Comment on egusphere-2022-1103', Anonymous Referee #3, 09 Jan 2023
General comments:
The paper entitled “Can the combining of wetlands with reservoir operation largely reduce the risk of future flood and droughts?” is an interesting work that integrates wetlands as nature-based solution for mitigation of flood and droughts in modelling. This work helps improve the understanding of how to integrate wetlands into hydrological models as well as how wetlands can be used for hydrological assessments. I believe it deserves publishing but with major revisions.
This paper is a long and sometimes repetitive read in which it is easy to lose track of all the given information. Overall, the article could be more condensed and straightforward. Moreover, some clarification concerning the modeling approach, more explicit description of the methods as well as better connection to the aim and research questions is needed. For instance, the work of future projection of flood and droughts are given more space than could be understood in the aim and research questions and also compare to what the reader initially would think regarding the focus on wetlands with reservoir operations as mentioned in the title. It is not clear how this study comes to the conclusions regarding how wetland and reservoir operation reduces the risk of future floods and droughts. I believe this should be the main aspects of the results and discussion. In addition, the results and discussion should better reflect the fact that this work is based on a case study and that local conditions/mitigations from wetlands combined with reservoir operation could vary between river basins.
Specific comments
Introduction- very long and repetitive introduction that can be condensed to the most important and relevant aspects of the study.
Line 47:what do you mean by cascade up the flood risks to a great extent?
Line 53-68 if you are referring to wetlands as NBS, why not write it in a same unifying paragraph?
Line 74-75 what do you mean by hydrologic equivalent wetland
Line 76-77: instead of typing all the references, you could shorten and simplify the reading to “ multiple studies (e.g., references)”
Line 93-95: sentences that could be rewritten into previous sentence inline 91-93
Line 95-96: how is this information relevant to the study?
Line 115: what is meant by the expression “ 1+1=2” simulation effect?
Line: 137: I think it is worth mentioning and clarifying that you use the Nenjiang river basin as a case study to answer the aim of the effect of wetland and reservoir operations into hydrological modelling for mitigating future flood and drought.
Line141: the main research questions are not clear enough. My understanding is that you want to analyze how the combined wetland and reservoir operation can mitigate flood using modelling. So the (a) question should be written in that direction and the question (b) might be oriented towards the mitigation of wetlands and reservoir operations of future flood and drought.
Methods- To many sections that are repetitive and could be deleted/incorporated into eachother and with fewer sections.
Line 160: what is meant by “the wetlands and their contributing areas within the reaches”?
Line 164-165: you should delete that information. You already mention that the lower NRB is an important agricultural area.
Line 166: what is meant by “ecological integrity”?
Line 168-171: these two sentences could be shorten into one.
Line 177: Could you give a percentage of the total catchment instead? It would give more understanding of how important the area that drains into the reservoir if it was in percentage of the total catchment.
Line 181: It would be easier to read the figure 1 if less background information was there. Also, the (b) and (c) part of the figure is missing.
Line 190: In relation to Table 1, could you use the ID of the hydrological stations in figure 1 as well? It could be good to have a link between figure 1 and table 1.
Line 193. Section 2.2 might be superfluous in the paper and not really relevant as the study approach should be clear from the beginning. You should consider integrating this information in coming sections.
Line 213: Section 2.3 is too short for the reader to understand how the hydrological modeling coupled the wetlands and reservoir operation.
Line 220-221: please clarify “The simulated runoff simulated by hydrologic- wetland model at the reservoir outlet was replaced with the estimated reservoir outflow, thus integrating reservoir operation into the hydrological modeling (i.e. hydrologic-wetland-reservoir model)”
Line 226: section 2.3.1 could be integrated to the overall section of 2.3.
Line 229-231: this sentences could be integrated and refereed to above sentence in line 227-229.
Line 243: Please clarify the concept of a “hydrologically equivalent wetland”?
Line 255 & 257: You quite some abbreviations in the text, could you delete some and use the full word instead? For instance RW and IW could just be fully written out in order to facilitate the reading.
Line 263: To better understand how you set the model, could you consider to more explicitly describe how you integrate the reservoir operation into one common section, ex: 2.3 together with the coupling of wetlands? Your section 2.3 is very long and could be more condensed into one section about the set up of the model.
Line 266: What are the three algorithms?
Line 291-294: as the water level limit is always 216 m, could this sentence be rewritten in order to better understand the thresholds?
Line 294-295: I sis not clear what the 25.3 % of the daily streamflow? Is it the average daily streamflow of the year or of the dry season?
Section 2.3.3 could be better integrated into the overall section of the model set up together with the other above sections.
Section 2.4 and its subsection could also be better streamlined into one section describing the projection of future flood and drought.
Line 383-389: Information that might be to detailed and should be mentioned rather swiftly than given too much attention.
Line 433-434: repetitive sentence
Line 457-459: repetitive sentence of information already given before.
Results- Your result should better reflect the modelling work. Instead of referring to the result figures in the supplementary materials, you should integrate them into the main text. In that way you should give more credit to how the model perform with couple wetland and reservoir operation that focusing on the projection of future flood and droughts.
I would also recommend to use figure 5 &8 in text and leave figure 4 &7 in supplementary.
Figure 6 should be better explained and the explanation of the different plots (a-f) is missing.
Line 619: please clarify the statement “droughts will equivalent to the historical period”
Discussion- Overall, your discussion section is less focused on the results of the work. You give statements that reflect the results but you tend to use that as reference to other research work. Sometimes, the discussion is too general and should be better connected to the aim and research questions and notably to the case study.
Line 714: you state that “ such model performance improvement can minimize uncertainties” but is this the case for this analysis?
Line 736-744: It is not clear how this is related to the results of this work.
Section 4.5 could be deleted and integrated in the overall discussion of the results.
Line 831: “1 km resolution DEM” is information that should be mentioned earlier in the method part.
Technical corrections: typing errors, etc.
Line 219: delete “simulated”
Line 432: delete “characteristics”
Line 454: delete “The cumulative number of days during a drought event” as you repeat it just after the “i.e.,” .
Line 759: “needs an extensive assessment”
Citation: https://doi.org/10.5194/egusphere-2022-1103-RC3 - AC3: 'Reply on RC3', Guangxin Zhang, 15 Feb 2023
Yanfeng Wu et al.
Yanfeng Wu et al.
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