Round 1

Reviewer 1 Report

Although the authors have tried to make a lot of modifications, there are still problems such as not good enough organization, rigorous presentation, and not detailed data-method descriptions. The details are as follows:

Lines 89-90. I believe the results of the study not only provide a reference for Beijing wetlands, but also for wetlands or study areas with similar problems.

Study area. The section on the presentation of meteorology, hydrology, groundwater, etc. in the study area involves specific data and results, please specify if they are your own statistics. Otherwise, it is recommended to add citations to the manuscript.

Lines 124-127. Is the spatial resolution of the data in meters? Where did you download the remote sensing data? The ENVI software should do more with the data than just atmospheric correction before using.

Line 134. I noticed that the name of this data service center has now been changed, please check and correct. Reference URL: http://data.cma.cn/

Lines 143-144. The initials of Science, Data and Center need to be capitalized.

 

Lines 147-149. The authors obtained 6 remote sensing for 2005, 2007, 2009, 2011, 2014 and 2020, why only 2000 and 2020 were selected for land use analysis? Also, why are Table 2 and Figure 3-7 in the latter part of the manuscript both based on land use in 2005 and 2020?

 

Lines 216-219. This section should be moved to the methods section.

 

In parts 3.2 and 3.3 of the text, it is recommended that the results of the study should be presented visually instead of being presented in such a compartmentalized form.

 

In subsection 3.4.3, what is the significance level of the trend of annual temperature and precipitation? What are the test results? What is the Z index as calculated by P index or Mann-Kendall?

 

Line 349. The text only mentions the evapotranspiration estimated based on the P-M formula. Is the result reliable and is it testified by specific observation data?

 

Lines 350-353. The authors only analyze the temperature and precipitation trends during the historical period, without presenting any information about future climate change in the study area. Here, however, the impact of future climate change on the evolution of water resources in the study area is stated, which is really inappropriate!

 

I still have not seen an in-depth discussion that is pleasing to the eye. Although the author attempts some discussion later in the Conclusion from the perspective of the technical methods employed and the implications for wetland restoration and conservation, these are generalized.

Author Response

Reviewer #1

General Comments: Although the authors have tried to make a lot of modifications, there are still problems such as not good enough organization, rigorous presentation, and not detailed data-method descriptions. The details are as follows:

Response: Thanks for your positive evaluation and constructive comments. Below please find our point-to-point response to your specific comments.

Specific Comments:

Comments (1): Lines 89-90. I believe the results of the study not only provide a reference for Beijing wetlands, but also for wetlands or study areas with similar problems. Study area. The section on the presentation of meteorology, hydrology, groundwater, etc. in the study area involves specific data and results, please specify if they are your own statistics. Otherwise, it is recommended to add citations to the manuscript.

Response (1): Thanks for your suggestions. We have revised this sentence as suggested (Lines 35-38):

“The research results can provide a theory for the protection and restoration of wetlands with similar problem.”

We added the related reference to support the information for study area (Lines 116-123) :

“It is the primary source of the Hanshiqiao water area. The wetland is located in the alluvial fan of Chaobai River, belonging to the temperate and semi-humid continental monsoon climate (Zhang et al. 2007). The precipitation in the wetland area is moderate, concentrated in 6.8 months, which is easy to form surface runoff, becoming a good condition for the formation of the wetland (Liu et al. 2008). Due to the higher terrain on the south, north and east sides of the periphery, rainwater and groundwater flow from three sides to the west depression, forming a water collecting area. For this reason, the region has historically been hit by floods (Zhang 2007).”

Comments (2): Lines 124-127. Is the spatial resolution of the data in meters? Where did you download the remote sensing data? The ENVI software should do more with the data than just atmospheric correction before using.

Response (2): Yes, satellite images' spatial resolution ranges from 0.5 to 0.6 meters. We added a table and figure to show detailed information about the satellite images used in the revision as follow (Line143-146):

  “This paper selected high-resolution satellite remote sensing data of Hanshiqiao Wetland Reserve in each season of 2005, 2007, 2009, 2011, 2014 and 2020 as the primary data source basically without cloud interference. More detailed information is shown in Table. 1 and Figs. 2.”

Additionally, we added more information about the preprocess by ENVI software in revision (Line 146-149):

“ENVI 5.3 software was used to preprocess the images, including atmospheric correction, geometric correction, and so on. In addition, we interpret the main land-use types of remote sensing images using the supervised classification method in ENVI and then refine the results through visual interpretation.”

Comments (3): Line 134. I noticed that the name of this data service center has now been changed, please check and correct. Reference URL: http://data.cma.cn/

Response (3): Thanks for your suggestions. We have corrected the URL in revision.

Comments (4): Lines 143-144. The initials of Science, Data and Center need to be capitalized.

Response (4): Corrected as suggested.

Comments (5): Lines 147-149. The authors obtained 6 remote sensing for 2005, 2007, 2009, 2011, 2014 and 2020, why only 2000 and 2020 were selected for land use analysis? Also, why are Table 2 and Figure 3-7 in the latter part of the manuscript both based on land use in 2005 and 2020?

Response (5): The scale scope of the two analysis results is different. What we analyzed in Figure 2 is the land use change of the whole upper reaches of Hanshiqiao River basin, so we used the land use classification map with a resolution of 30 meters.  However, the resolution of 30m data is too rough for Hanshiqiao wetland.  Therefore, we must use the high-resolution (0.5~0.6m) remote sensing images for interpretation to obtain land use change and hydrological connectivity evolution of Hanshiqiao wetland.  High resolution remote sensing is only available after 2005. 

Comments (6): Lines 216-219. This section should be moved to the methods section.

Response (6): Corrected as suggested.

Comments (7): In parts 3.2 and 3.3 of the text, it is recommended that the results of the study should be presented visually instead of being presented in such a compartmentalized form.

Response (7): Corrected as suggested

Comments (8): In subsection 3.4.3, what is the significance level of the trend of annual temperature and precipitation? What are the test results? What is the Z index as calculated by P index or Mann-Kendall?

Response (8): We updated the Table S1 in revision and added the clarity about how to

Comments (9): In subsection 3.4.3, what is the significance level of the trend of annual temperature and precipitation? What are the test results? What is the Z index as calculated by P index or Mann-Kendall?

Response (9): In this revision, we add the introduction for the calculation method of long-term trend and corresponding estimation method of trend uncertainty (Line 239-241):

“For the statistical analyses, the long-term trends of variables were evaluated by linear regression. The Mann-Kendall test was performed for the statistical significance of trends, and 95% confidence intervals were provided for all trends (Du et al. 2020; Mann 1945).”

We added the confidence interval for the trend of temperature and precipitation in Figure 8 and give a detailed introduce in the caption (Line 680-682):

“The temperature and precipitation changes for Hanshiqiao Wetland (a and b) and its upstream watershed (c and d) during 1960-2020. The trend denotes the temperature and precipitation trend, and p represents the p-value for the significance test for trends.”

Comments (10): In Line 349. The text only mentions the evapotranspiration estimated based on the P-M formula. Is the result reliable and is it testified by specific observation data?

Response (10): The P-M formula method has been widely applied to estimate evapotranspiration in the Beijing area and achieved excellent results. We explain this in the revised paper and cite relevant existing studies as examples (Line 161-163):

“Previous studies have proved that the ET calculated by the Penman-Monteith equation agrees well with the actual evapotranspiration in Beijing, used to evaluate other methods. (Haijun et al. 2013; Yang et al. 2017).”

Comments (11): I still have not seen an in-depth discussion that is pleasing to the eye. Although the author attempts some discussion later in the Conclusion from the perspective of the technical methods employed and the implications for wetland restoration and conservation, these are generalized.

Response (11): We have not set a special section for discussion. After we present the results in the Results section, we will discuss the results accordingly. We think this will make it easier for readers to understand what we're saying. Secondly, we discussed the limitations of the method in the conclusion section.

Author Response File: Author Response.docx

Reviewer 2 Report

The paper is interesting due to it refers to the hydrological connectivity of urban wetland wetlands. A topic was less developed in the literature which can help determine actions for wetland conservation and restoration. Meanwhile, the introduction is too methodological, we need more context to a wetland situated in a density city, i.e. what is happening in China with wetlands? what is the question and problem to resolve with a spatial methos of hydrological connectivity and why is the connectivity for the hydrological flows in the city ?

To know better the case study could you add a photo of Hanshiqiao wetland

 

Doubts that we author have to be clear

 

1. Which Satellites images are used which sensor 
2. Which statistical test of accuracy are used
3. Which does not distinguish a native forest and exotic due to the influences in hydrological sediments and nutrients. Also it can affect the stability of the basin
4. Which are the main actions of the restoration process
5. Which are the driver's factors of fragmentation 
6. Which stakeholders have to provide water security to  Hanshiqiao Wetland

 

Figures 

I can not see in figure 1a the surface of Hanshiqiao (red square) - F.1c Why some weather stations are outside of the elevation model - F.1d What are the green lines?

Author Response

Reviewer #2

General Comments: The paper is interesting due to it refers to the hydrological connectivity of urban wetland wetlands. A topic was less developed in the literature which can help determine actions for wetland conservation and restoration. Meanwhile, the introduction is too methodological, we need more context to a wetland situated in a density city, i.e. what is happening in China with wetlands? what is the question and problem to resolve with a spatial method of hydrological connectivity and why is the connectivity for the hydrological flows in the city?

Response: Thanks for your positive evaluation and constructive comments. We added a more information about the urban wetland in China in revision as your suggestion (Line 83-93):

“With rapid urbanization, the area of urban wetland has been degraded in China (Kumwimba et al. 2021; Song et al. 2020). The wetlands not only lack water and have been polluted significantly due to climate change and human overuse of water. The core wetland is gradually fragmented into small patches, the wetland's ecological function is depleted, and the urban wetland's biodiversity is reduced considerably. This phenomenon is more evident in Beijing, Shanghai, and other supercities (Meng et al. 2017; Xia et al. 2019). As a typical natural wetland in Beijing, Hanshiqiao Wetland has undergone significant changes due to the disturbance of climate change and human activities. Therefore, it is helpful to understand the evolution characteristics and driving factors of urban wetlands by studying the hydrological connectivity evolution characteristics of the Hanshiqiao wetland (Cui et al. 2021b; Zhang et al. 2011a).”

Below please find our point-to-point response to your specific comments.

Specific Comments:

Comments (1): Which Satellites images are used which sensor

Response (1): Thanks for your suggestions. We have added a Table 1 to introduce the detailed information of satellite images in revision.

Comments (2): Which statistical test of accuracy are used

Response (2): In this revision, we add the introduction for the calculation method of long-term trend and corresponding estimation method of trend uncertainty (Line 239-241):

“For the statistical analyses, the long-term trends of variables were evaluated by linear regression. The Mann-Kendall test was performed for the statistical significance of trends, and 95% confidence intervals were provided for all trends (Du et al. 2020; Mann 1945).”

Comments (3): Which does not distinguish a native forest and exotic due to the influences in hydrological sediments and nutrients. Also, it can affect the stability of the basin.

Response (3): There are significant differences in the influence of native forests and exotic forests on the regional water cycle. However, we do not have relevant land use data to distinguish the native forest from the exotic forest at present, so we can further explore this problem in the future. Therefore, we added a sentence to the paper to illustrate this problem (Line 261-265):

    “Note that our land use classification is relatively simple, unable to explore some more complicated problems. For example, the native forest of the basin water cycle and nutrition change significantly differ from the exotic forest in hydrological sediments and nutrients. However, we still cannot effectively distinguish them now and hope to explore this problem in the future.”

Comments (4): Which are the main actions of the restoration process.

Response (4): Thanks for your suggestions. We added a detailed introduction for the restoration process of the wetland in revision (Line 135-141).

“Due to a lack of protection for a long time, the Hanshiqiao wetland has degraded (Liu et al. 2008). In 2005, after establishing the Hanshiqiao Wetland Nature Reserve, they carried out several restoration measures to the wetland. The wetland restoration process mainly includes three aspects: first, they are wide and clean the river, which improves the connectivity of the river; Secondly, they take the farmland and aquaculture ponds back and transform them into wetlands; they build a sewage processing plant to collect sewage from nearby towns, replenish and recharge them to the wetland.”

Comments (5): Which are the driver's factors of fragmentation

Response (5): According to existing studies, we added the explanation for the fragmentation of wetland before 2005 (Line 135-136):

“Due to a lack of protection for a long time, the Hanshiqiao wetland has degraded (Liu et al. 2008).”

Comments (6): Which stakeholders have to provide water security to Hanshiqiao Wetland.

Response (6): Hanshiqiao Wetland Reserve was established by the state, so there are no stakeholders who have to provide water security to Hanshiqiao wetland.

Comments (7): I can not see in figure 1a the surface of Hanshiqiao (red square) - F.1c Why some weather stations are outside of the elevation model - F.1d What are the green lines?

Response (7): Firstly, we indicate the location of the Hanshiqiao Wetland in the revised. Secondly, the area of Hanshiqiao is minimal, and there is no surface weather station for long-term observation inside the wetland. Therefore, we use the observation data of the surface weather stations around the wetland to study this area's regional climate change characteristics. The green lines in Figure 1 indicated “Drain” rather than “Brain”, which is a spelling error. We have corrected it in revision.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper aims to apply and validate a newly proposed method namely  Morphological Spatial Pattern Analysis (MSPA) with the Connectivity Index (IIC, Integral Index of Connectivity on the Hydrological connectivity; It is well written. Valuable results and insights have been obtained.

However, I have a question about the time series of high spatial resolution data employed in the experiments. 

Since no details were described in the paper. I strongly suggest metadata of these data are listed in detail in the revision, especially the acquisition time of the data. A related concern is how the Authors deal with seasonal changes which may bring uncertainty in the classification map as the study is on a yearly basis. 

Author Response

General Comments: The paper aims to apply and validate a newly proposed method namely Morphological Spatial Pattern Analysis (MSPA) with the Connectivity Index (IIC, Integral Index of Connectivity on the Hydrological connectivity; It is well written. Valuable results and insights have been obtained. However, I have a question about the time series of high spatial resolution data employed in the experiments. Since no details were described in the paper. I strongly suggest metadata of these data are listed in detail in the revision, especially the acquisition time of the data. A related concern is how the Authors deal with seasonal changes which may bring uncertainty in the classification map as the study is on a yearly basis.

Response: Thanks for your positive evaluation and constructive comments. We added a table and figure to show detailed information about the satellite images used in the revision as follow (Line 143-146):

  “This paper selected high-resolution satellite remote sensing data of Hanshiqiao Wetland Reserve in each season of 2005, 2007, 2009, 2011, 2014 and 2020 as the primary data source basically without cloud interference. More detailed information is shown in Table. 1 and Figs. 2.”

Round 2

Reviewer 1 Report

The authors have revised and improved the abstract, preface and research methods sections to broadly meet the level required by the journal. However, the manuscript still has room for improvement. 

1. I found that the title and the research content do not correspond. The authors' research is mainly focused on hydrological connectivity, but the title is too large and far beyond the scope of this study. I would suggest a revision.
2. I think the author can refer some literatures in the discussion part to further enrich the section.
3. The conclusion is not a repetitive copy of the findings of the study, but a summary and overview of the findings of the study. Suggest changing 'Conclusion' to 'Summary and Conclusion' and, at the same time, refining and condensing the content.

Author Response

General Comments: The authors have revised and improved the abstract, preface and research methods sections to broadly meet the level required by the journal. However, the manuscript still has room for improvement.

Response: Thanks for your positive evaluation and constructive comments. Below please find our point-to-point response to your specific comments.

Specific Comments:

Comments (1): I found that the title and the research content do not correspond. The authors' research is mainly focused on hydrological connectivity, but the title is too large and far beyond the scope of this study. I would suggest a revision.

Response (1): Thanks for your suggestions. We changed the title to “Hydrological connectivity of Hanshiqiao wetland and its response to climate change and human activities”.

 

Comments (2): I think the author can refer some literatures in the discussion part to further enrich the section.

Response (2): Thanks for constructive comments. We added relevant existing studies to enrich the discussion part in revision. For example:

In Line 362-364：

“For example, the native forest of the basin water cycle and nutrition change significantly differ from the exotic forest in hydrological sediments and nutrients (Fierro et al. 2017; Yu et al. 2019).”

In Line 410-413:

“Besides air temperature, evapotranspiration is also affected by other factors such as wind speed, which may be why air temperature may have a more negligible effect on hydrological connectivity than precipitation and evapotranspiration (Liu and Zhang 2013; Valipour 2015).”

Comments (3): The conclusion is not a repetitive copy of the findings of the study, but a summary and overview of the findings of the study. Suggest changing 'Conclusion' to 'Summary and Conclusion' and, at the same time, refining and condensing the content.

Response (3): Corrected as suggested.

 

Author Response File: Author Response.pdf

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Dear Authors,

Topic if this article is of interest to scientists and managers. However, this manuscript is very short providing insufficient details on methods, their background. Also, some methods (e.g. trend analysis of climate data) were totally absent in methods section. Results section needs more details of results instead of discussion. Discussion section needs to include discussion of results of this study with other similar studies and/or significance. Article needs substantial reorganization befor further consideration. Also, the language is difficult to understand at many places and needs a through review from a native English speaker.

Reviewer 2 Report

This paper explored the evolution mechanism of hydrological connectivity of Hanshiqiao wetlands using six high-resolution remote sensing images spanning 2005-2020. The climatic and anthropogenic driving on hydrological connectivity change were discussed. This is an interesting work and the case study can provide useful references for wetland restoration. The methodology is ok and the manuscript is well organized. However, the Discussion part is too weak. I recommend a major revision.

Specific comments:

1. Lines 16-17. Please remove these texts from the manuscript.
2. Line 126, what’s the unit of spatial resolution?
3. The article not adequately referenced. Please add the key reference in the Study Area, Method and Discussion. It is impossible/abnormal to find none of reference when writing Discussion in a manuscript.
4. I recommend to an individual structure of Discussion with further arguments. The purpose of the discussion is to interpret and describe (i) the significance of your findings in light of what was already known about the research problem being investigated, and (ii) to explain any new understanding or fresh insights about the problem after you've taken the findings into consideration. I cannot find the above two points from the manuscript.
5. The format of references is inconsistency.
6. Line 444. Please add the full name of IIC and PC in the title of Fig.3.
7. Please give the method used for texting and how to determine the significant level of change trend in the manuscript.

Reviewer 3 Report

1. The main results are obtained based on the high-resolution satellite images acquired in different year. It is better to provide the detailed imaging parameters of those images, including sensors and acquisition dates, which are important for readers to estimate the influence of the intra-year variation of wetland.
2. What classification methods are used for extracting land cover information from the images?
3. Line 135, what the 95% stands for? Overall accuracy? Producer’s or user’s accuracy? I suggest to provide a classification error matrix with accuracy statistics.
4. This study divided the spatial morphological evolution of Hanshiqiao wetland into two phases, namely, the recovery stage and the stable stage. How these two stages were determined and divided? Observing Figures 3 and 6, I did not see significant difference between these two stages.
5. The authors used the MSPA and IIC and PC for analyzing the hydrological connectivity variation. What are the advantages of integrating these two methods? It seems that the authors only used two independent methods for the analysis. I did not find the integration of these two methods.
6. Lines 41-44, “The combined method of the MSPA model and connectivity index can better reveal the changing rules of hydrological morphology, organization and operation in wetland hydrological connectivity change, which can provide a methodological reference for other wetland related research.”. Better than what? I did not find any comparison between your method and other commonly used methods.
7. The discussion and conclusion should be separated. Otherwise, it is difficult for readers to get the significant findings and contribution made by this study.
8. Lines 130-131, “the supervision of the study area was classified into four categories: lake, reed, river and green land/building land”. This sentence does not make any sense. Please revise it.