Round 1

Reviewer 1 Report

Comments and Suggestions for Authors The manuscript entitled "Seasonality and predictability of hydrometeorological and water chemistry indicators in three coastal forested watersheds". I consider minor revision is required due to a bit English typo and/or minor grammatrical mistakes, and missing a section "limitations of this study".    Major comment: El Niño–Southern Oscillation (ENSO) should affect substantially to the result. Authors did not even mention about it. Since they did not assess it, so at least you should write a paragraph stating the limitations of this study.    For instance, it will be helpful to read the below references for writing the limitations of this study: Thi Ha, D., Ouillon, S., & Van Vinh, G. (2018). Water and suspended sediment budgets in the lower Mekong from high-frequency measurements (2009–2016). Water, 10(7), 846. Fok, H. S., Chen, Y., Ma, Z., Ferreira, V. G., & Tenzer, R. (2023). Geographically-weighted water balance approach for satellite-hydrologic runoff estimation in Mekong Basin under ENSO. International Journal of Applied Earth Observation and Geoinformation, 118, 103234. He, Q., Chun, K. P., Fok, H. S., Chen, Q., Dieppois, B., & Massei, N. (2020). Water storage redistribution over East China, between 2003 and 2015, driven by intra-and inter-annual climate variability. Journal of Hydrology, 583, 124475.   Comments on the Quality of English Language Minor comment: Even the first sentence of the abstract has a typo or English expression problem. It is not nice. "Forests are recognized for sustaining good water chemistry within landscapes. water chemistry." Either delete "water chemistry" or rewrite it to include the keyword "water chemistry". etc..

Author Response

We greatly appreciate the Editor and Reviewers for the constructive comments and suggestions. We agree with Editor’s and Reviewers’ comments which helps to enhance the manuscript quality. Accordingly, we improved version of the paper by revising following the comments and submitted to the Sustainability journal. Please find also attached a point-by-point response to the Reviewers’ concerns. We hope that our responses will be satisfactory. All changes in manuscript were marked in red color.

Comment: The manuscript entitled "Seasonality and predictability of hydrometeorological and water chemistry indicators in three coastal forested watersheds". I consider minor revision is required due to a bit English typo and/or minor grammatical mistakes, and missing a section "limitations of this study".    Major comment: El Niño–Southern Oscillation (ENSO) should affect substantially to the result. Authors did not even mention about it. Since they did not assess it, so at least you should write a paragraph stating the limitations of this study.    For instance, it will be helpful to read the below references for writing the limitations of this study: Thi Ha, D., Ouillon, S., & Van Vinh, G. (2018). Water and suspended sediment budgets in the lower Mekong from high-frequency measurements (2009–2016). Water, 10(7), 846. Fok, H. S., Chen, Y., Ma, Z., Ferreira, V. G., & Tenzer, R. (2023). Geographically-weighted water balance approach for satellite-hydrologic runoff estimation in Mekong Basin under ENSO. International Journal of Applied Earth Observation and Geoinformation, 118, 103234. He, Q., Chun, K. P., Fok, H. S., Chen, Q., Dieppois, B., & Massei, N. (2020). Water storage redistribution over East China, between 2003 and 2015, driven by intra-and inter-annual climate variability. Journal of Hydrology, 583, 124475.  

 

 

Comments on the Quality of English Language

Minor comment: Even the first sentence of the abstract has a typo or English expression problem. It is not nice. "Forests are recognized for sustaining good water chemistry within landscapes. water chemistry." Either delete "water chemistry" or rewrite it to include the keyword "water chemistry". etc..

 

Authors’ answer:

Thank you, Reviewer, for your valuable comments and suggestions. In the revised manuscript, we have added section 4.2.5, Limitations of the Study, where we explain that Hurricane Joaquin was the main factor influencing hydrology and water chemistry seasonality in the analyzed watersheds. In the authors' opinion, the ENSO effect did not impact the analyzed factors during the 2011–2019 period. In the improved version of the paper, we have included the suggested references. We have carefully reviewed the paper again and improved the English grammar. We apologize for those two unnecessary words “water chemistry” at the end of the 1^st line in the Abstract.

 

“4.2.5. Limitations of the study

 

In this study, the main factor influencing hydrological processes and water chemistry in later study period on the coastal forested watersheds was Hurricane Joaquin, which occurred on October 3-4, 2015, yielding > 300 mm rain in 48 hours that inundated much of the lowlands with extreme discharge. It is commonly known that the El Niño–Southern Oscillation (ENSO) can affect runoff variability and sediment transport, as reported by Thi et al. [74] in the Lower Mekong. Furthermore, Park et al. (2024) noted that the winter Atlantic Niño exerts a significant and greater effect on ENSO compared to the summer Atlantic Niño. In the present study, the effect of ENSO on hydrology and water chemistry variability was not included. The factor that influenced the seasonality and predictability of hydrological indicators and water chemistry was extreme outflow produced by intense and prolonged precipitation, as indirect effects of Hurricane Joaquin staying just off the Atlantic coast near the study site. Amatya et al. [28] assumed that extreme outflow that occurred on two study watersheds (WS77 and WS80) as outliers in their paired calibration relationships. With its inclusion, the paired flow relationship had higher R² but was biased due that single extreme outflow. This hurricane, which did not have tropical origins—a rare occurrence for a major hurricane—only indirectly contributed to these hazardous conditions. Contributing to the coastal flooding was a strong pressure gradient off the New England coast behind a frontal boundary, producing a long fetch of northeasterly gales directed at the mid-Atlantic coast at the start of the month, while tides were already running higher than normal [75].

Another limitation of the study is that only in situ data were used to analyze the seasonality and predictability of hydrological and water chemistry indicators. Satellite-based hydrometeorologic observations could have supplemented in-situ observations and provided deeper insights into water balance and the seasonality of the analyzed variables, including other environmental factors such as soil moisture and vegetation parameters like leaf area index and their seasonality [76]. One other possible limitation is that forests on these watersheds were substantially damaged by winds of Hurricane Hugo in 1989 and were reported as fully recovered by 2004 [32]. However, Joaquin’s impacts were more on flooding than the forest damage.

To analyze the relationships between meteorological, hydrological, and water chemistry factors more in-depth, multidimensional statistical analyses such as principal component analysis (PCA) could be used [20, 77). Unfortunately, in this case, PCA was not possible due to missing data, particularly water chemistry, during extreme hydrological events.”

 

74. Thi Ha, D., Ouillon, S., Van Vinh, G.. Water and Suspended Sediment Budgets in the Lower Mekong from High-Frequency Measurements (2009–2016). Water. 2018, 10(7), https://doi.org/10.3390/w10070846
75. Berg, R., Hurricane Joaquin (AL112015), 28 September – 7 October 2015, National Hurricane Center Tropical Cyclone Report, 2016
76. Fok, H. S., Chen, Y., Ma, Z., Ferreira, V. G., Tenzer, R.  Geographically-weighted water balance approach for satellite-hydrologic runoff estimation in Mekong Basin under ENSO. International Journal of Applied Earth Observation and Geoinformation, 2023,  118, 103234. https://doi.org/10.1016/j.jag.2023.103234
77. He, Q., Chun, K.P., Sum Fok, H., Chen, Q., Dieppois, B., Massei, N.. Water storage redistribution over East China, between 2003 and 2015, driven by intra- and inter-annual climate variability. Hydrol. 2020, 583, 124475. https://doi.org/https://doi.org/10.1016/j.jhydrol.2019.124475

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presents a representative sample of field studies and the analytical processing of their results. The authors' objective is to test the hypothesis that there is a correlation between hydrological parameters and the chemical composition of water, and extreme meteorological events. Furthermore, the research is not based on a single study, but rather encompasses three distinct coal regions. In this regard, the work is undoubtedly relevant and useful to the scientific community.

 

It should be noted at once that the presented work is of a considerable length and depth of analysis, comparable to the output of a PhD thesis. A sufficient period of time is required to evaluate the results. Nevertheless, the authors employ clearly defined and accredited methods in their work. The results of field studies conducted at different time points for each of the watersheds are presented in great detail. Further calculations, a reasoned presentation of results, and their visualisation allow readers not only to understand the data obtained by the authors, but also to transpose them to other study areas.

In this regard, it is the opinion of the reviewer that this work can be useful both in terms of scientific results and practical application, including in the educational process.

Author Response

Comments: The manuscript presents a representative sample of field studies and the analytical processing of their results. The authors' objective is to test the hypothesis that there is a correlation between hydrological parameters and the chemical composition of water, and extreme meteorological events. Furthermore, the research is not based on a single study, but rather encompasses three distinct coal regions. In this regard, the work is undoubtedly relevant and useful to the scientific community.

It should be noted at once that the presented work is of a considerable length and depth of analysis, comparable to the output of a PhD thesis. A sufficient period of time is required to evaluate the results. Nevertheless, the authors employ clearly defined and accredited methods in their work. The results of field studies conducted at different time points for each of the watersheds are presented in great detail. Further calculations, a reasoned presentation of results, and their visualisation allow readers not only to understand the data obtained by the authors, but also to transpose them to other study areas.

In this regard, it is the opinion of the reviewer that this work can be useful both in terms of scientific results and practical application, including in the educational process.

 

Authors answers: Thank you, Reviewer, for your positive feedback on the paper. We agree that the manuscript is lengthy, but we analyzed various factors, such as hydrology and water chemistry, and aimed to show the relationships between their seasonality and predictability using rather a long period of data. Additionally, we wanted to provide a detailed explanation of the observed behaviors. We think that such details of explanation using different factors and their influences on seasonality of hydrochemistry characteristics of forested watersheds would be very useful for readers as well as forest management.

 

Reviewer 3 Report

Comments and Suggestions for Authors

Critical response for the manuscript entitled “Seasonality and predictability of hydrometeorological 2

and water chemistry indicators in three coastal forested water-3

sheds” submitted by Andrzej Wałęga and coauthors 

 

The labor under consideration presented a serious result of research dedicated to hydrochemical parameters predicability in their connection with landscape peculiarities and seasonality. Authors study landscapes both with  load of human activities and without one. Authors compare two five years time spans: before and after Joaquin hurricane. The convincingly proved that extreme hydrometeorological events change patterns in natural processes and hence predictability of hydrology and water chemistry parameters. Authors cite signifint number of published papers (73), map of research site and plots  are of good quality.

As a part of criticism I would recommend to imply novel machine learning methods to model hydrological system behaviour. Also, describtion seems a bit wordy and may require shortening. 

Aside of it, paper deserves publication 'as is' withot necessary further improvements.

Author Response

Comment: Critical response for the manuscript entitled “Seasonality and predictability of hydrometeorological and water chemistry indicators in three coastal forested watersheds” submitted by Andrzej Wałęga and coauthors 

The labor under consideration presented a serious result of research dedicated to hydrochemical parameters predicability in their connection with landscape peculiarities and seasonality. Authors study landscapes both with  load of human activities and without one. Authors compare two five years time spans: before and after Joaquin hurricane. The convincingly proved that extreme hydrometeorological events change patterns in natural processes and hence predictability of hydrology and water chemistry parameters. Authors cite signifint number of published papers (73), map of research site and plots  are of good quality.

As a part of criticism I would recommend to imply novel machine learning methods to model hydrological system behaviour. Also, describtion seems a bit wordy and may require shortening. 

Aside of it, paper deserves publication 'as is' withot necessary further improvements.

Authors answer: Thank you, Reviewer, for your positive feedback on the paper. We did not include advanced modeling techniques, such as the widely popular machine learning, because we wanted to focus solely on observations. These techniques can be used to predict changes in climate and land use conditions. However, a challenge in using machine learning techniques is lack of missing data. In analyzed region is missing is the complete historical data prior to forest recovery after harvesting. This makes it difficult to predict the impact of future vegetation conditions on hydrochemical parameters.

Reviewer 4 Report

Comments and Suggestions for Authors

In this manuscript, statistical analyses of hydrological and stream water chemistry indicators were conducted for three coastal forested watersheds. Statistical significance of differences between analysis periods (2011-2014，2011-2019) and seasons and predictability of flow, precipitation, PET, WTE, etc. for each of the three watersheds were demonstrated. The influences of extreme events on hydrological factors and water chemistry were also explored. The manuscript is well prepared. The author's workload is relatively large, but the innovation of this manuscript needs further clarification. The significance of Colwell indicators in the study area has not been clearly described, what reference does this study have for other watersheds? If the authors focus on innovative methods, further systematization is needed for the description of this method.

 

Other comments are listed below.

Line 14-15:  “water chemistry” is not needed!

Figure 1: in the legend, the boundary of W78 is missing?

Table 1-3:  some units are incorrect, for instance, “mgL” should be “mg/L”.

Line 421-422: “values with statistically significant differences for α = 0.05 are shown in red color font.” There are not any values in red color font in Table 4.

 

Line 326:  “( See Appendix Table A1,……”.  Where is the other half of the bracket?

 

Author Response

We greatly appreciate the Editor and Reviewers for the constructive comments and suggestions. We agree with Editor’s and Reviewers’ comments which helps to enhance the manuscript quality. Accordingly, we improved version of the paper by revising following the comments and submitted to the Sustainability journal. Please find also attached a point-by-point response to the Reviewers’ concerns. We hope that our responses will be satisfactory. All changes in manuscript were marked in red color.

Comment: In this manuscript, statistical analyses of hydrological and stream water chemistry indicators were conducted for three coastal forested watersheds. Statistical significance of differences between analysis periods (2011-2014，2011-2019) and seasons and predictability of flow, precipitation, PET, WTE, etc. for each of the three watersheds were demonstrated. The influences of extreme events on hydrological factors and water chemistry were also explored. The manuscript is well prepared. The author's workload is relatively large, but the innovation of this manuscript needs further clarification. The significance of Colwell indicators in the study area has not been clearly described, what reference does this study have for other watersheds? If the authors focus on innovative methods, further systematization is needed for the description of this method.

 

Other comments are listed below.

Line 14-15:  “water chemistry” is not needed!

Figure 1: in the legend, the boundary of W78 is missing?

Table 1-3:  some units are incorrect, for instance, “mgL” should be “mg/L”.

Line 421-422: “values with statistically significant differences for α = 0.05 are shown in red color font.” There are not any values in red color font in Table 4.

 

Line 326:  “( See Appendix Table A1,……”.  Where is the other half of the bracket?

 

Authors answers: Thanks a lot to the Reviewer for the above valuable suggestions and positive opinions about the manuscript. We added a short paragraph in Conclusions to more clearly show significance of Collwell indicators in analysis of time series hydrochemical data. Please see at lines 836-845: “In conclusion, Colwell’s indicators are simple tools defined by statistical indicators compared to other more advanced statistical methods. They are useful for detecting similarities or differences in the behaviors of hydro-climatic time series and water chemistry indicators in paired watersheds. Knowledge about the behavior of these processes, assessed using simple indicators, can help detect disorders in hydrochemical time series caused by climate conditions or human activities. Additionally, they help analyze the influence of different mitigation techniques on the seasonality of time series. Colwell’s indicators, as a universal approach, can be used to detect the predictability and seasonality of various hydroclimatic and chemical parameters in watersheds. One limitation of using this method is the requirement for at least 10 years of time series data without gaps.” Give some other references where you published this method.

Other Reviewer’s comments

1. Line 14-15:  “water chemistry” is not needed!

Thank you for suggestion. “water chemistry” was now deleted

2. Figure 1: in the legend, the boundary of W78 is missing?

In Fig 1 the boundary of WS78 is marked in thick green color.

3. Table 1-3:  some units are incorrect, for instance, “mgL” should be “mg/L”.

Thank you for suggestions. The units are corrected

4. Line 421-422: “values with statistically significant differences for α = 0.05 are shown in red color font.” There are not any values in red color font in Table 4.

We are sorry for this mistake. Now we marked in Table 4 all statistical significance values in red color.

5. Line 326:  “( See Appendix Table A1,……”.  Where is the other half of the bracket?

Thank you for suggestion. The bracket was added

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

I have check the revised manuscript and found that most of my suggestions and comments were well addressed.  The comments and suggestions for the revised version are as follows.

My comment: Figure 1: in the legend, the boundary of W78 is missing?

The feed back of the authors: In Fig 1 the boundary of WS78 is marked in thick green color.

I mean that the "WS Boundary" should be added to the map legend  instead of “TC boundary” which will be more self-evident for readers to read the map.

Thus, the title of Figure 1 should be adjusted accordingly.

Because "SEF boundary" and  "TC boundary" are not the same classification category.

Line 794:  Please verify if punctuation is used correctly.

Further simplification is suggested for the section of " Summary and conclusions".

Author Response

Dear Editor and Reviewer

We greatly appreciate the Reviewer for providing few remaining constructive comments and suggestions during second round of peer-review process. We agree with the Reviewer’s comments which help to enhance the manuscript quality. Accordingly, we improved the version of the paper by revising it following the comments and submitted to the Sustainability journal. Please find also attached a point-by-point response to the Reviewer’s comments below. We hope that our responses will be satisfactory. All changes in manuscript were marked in red color.

 

Responds on reviewer’s comments

Comment: I have check the revised manuscript and found that most of my suggestions and comments were well addressed.  The comments and suggestions for the revised version are as follows. 

Authors answers: Thanks to the Reviewer for positive opinion about improved paper. Below are answers on additional comments

Comment: My comment: Figure 1: in the legend, the boundary of W78 is missing?

The feed back of the authors: In Fig 1 the boundary of WS78 is marked in thick green color.

I mean that the "WS Boundary" should be added to the map legend  instead of “TC boundary” which will be more self-evident for readers to read the map.

Thus, the title of Figure 1 should be adjusted accordingly.

 

Authors answers: Thank you for suggestions. In the revised version of the manuscript we changed the legend of TC boundary in fig 1 to the WS78 boundary. The caption of the figure was also modified as:

Figure 1. Location map of study watersheds WS77 (treatment) and WS80 (control) in the paired system and WS78 watershed, all within Francis Marion National Forest in coastal South Carolina.

 

Comment: Line 794:  Please verify if punctuation is used correctly.

Authors answers: We removed the punctuation from this sentence

 

Comment: Further simplification is suggested for the section of " Summary and conclusions".

Authors answers: Thanks again to the Reviewer for the suggestion. in " Summary and conclusions" section we actually wanted to provide some details on important results on hyphotheses tested. We mentioned how water chemistry and hydrochemistry were changed between seasons and periods. Because we were not quite sure to further simplify it, we 1) removed some redundant sentences, and 2) some in-depth analysed results s on  all three watersheds. Moreover, we more clarity rewritten some sentences. All changes are marked in red color.

Below is new version of Summary and conclusion:

5. Summary and conclusions

In this paper statistical analyses of hydrological and stream water chemistry indicators were conducted for three coastal forested watersheds located at US Forest Service Santee Experimental Forest in South Carolina, U.S.A. The analyses were performed for all indicators (flow, precipitation, potential evapotranspiration (PET), water table elevation (WTE), nutrients, dissolved oxygen, temperature, and conductivity) for each of the three watersheds using data for 2011-2019 period as a whole and individually for two periods of 2011-2014 before Hurricane Joaquin (October 2015) and after for 2015-2019. Additionally, hydrological and water chemistry indicators were compared for dormant (November - March) and growing (April – October) seasons between and within each of the periods. Analysis showed statistically significant differences between the seasons for flow, WTE and all water chemistry indicators in all the analyzed watersheds, except for temperature. The differences were observed particularly in the 2015-2019 period (post-Hurricane Joaquin) compared to 2011-2014 period. WTE and flow had the highest influences on water concentrations of nitrogen constituents. As expected, only the concentration of total dissolved phosphorus (TDP), a soluble part of phosphorus, slightly increased during storm events. Accordingly, it can be concluded that export of phosphorus to streams in this area  can mainly be attributed to shallow overland surface runoff during excessive rainfall events likely caused by saturation-excess runoff (water table flooding) due to the shallow water table position.  Regarding the difference between dormant and growing seasons, the highest differences were found in all watersheds for total dissolved nitrogen (TDN) and TDP, as water chemistry indicators, and WTE, PET, and precipitation, as hydrological indicators.

Colwell’s indicators showed a higher predictability for almost all hydrologic and water chemistry indicators in 2011-2014 period compared to 2015-2019. Seasonality for most of the water chemistry indicators increased in WS80 (control watershed) and WS77 in the second period, despite dominance of constancy (a measure that describes the tendency of a variable to remain unchanged for a given period of time) in their predictability but decreased in WS78 in the second period. The high contribution of constancy in total predictability shows similar variability in daily values for indicators in each of the years. The results also showed that similar hydrological processes on these low-gradient watersheds, that generally have shallow water table position (poorly drained soils), determined predictability of water chemistry concentrations in all watersheds. Similarity was observed mainly between watersheds with similar watersheds like WS80 and WS77, where predictability for the whole period was 0.56 and 0.53 for flow and 0.40 and 0.45 for the WTE, respectively. Similarity was mainly determined by similar hydrological, like flow and WTE and meteorological – precipitation and PET factors, that influenced on dynamic transport of chemical indicators to the stream. Predictability of hydrological indicators in WS78 was lower compared to WS80 and WS77 but seasonality was similar. Results of the analyses confirmed the first hypothesis; extreme hydro-meteorologic events, like hurricanes, can influence seasonality and predictability of hydrology and water chemistry indicators in forested streams.

In conclusion, Colwell’s indicators, as a universal approach, are simple tools compared to other more advanced statistical methods. They are useful for detecting similarities or differences in the behaviors of hydro-meteorological time series and water chemistry indicators in paired watersheds. Knowledge about the behavior of these processes, assessed using these indicators, can help detect disparities in seasonality and predictability of observed hydrochemical time series on watersheds caused by climate conditions or human activities. Additionally, they help analyze the influence of different mitigation techniques on the seasonality of time series. One limitation of using this method is the requirement for at least 10 years of time series data without gaps.

Furthermore, a different seasonality of TDP was observed on WS78 watershed compared to the smaller watersheds WS77 and WS80, likely due to (1) treatments in various years (e.g. thinning from 0.5% - 2.1% of the area as well as hazardous fuel treatment from 7% - 100% of the area)slower watershed response to precipitation, and (3) more heterogeneous soils compared to WS80 and WS77 that has a potential to influence on transport of phosphorus. Further studies should be focused on influence of harvesting, thinning, and hazardous fuel treatments on seasonality of hydrology and chemical indicators after 2019 where partial harvesting and thinning were performed on the WS77 for the purpose of restoring longleaf pine (Pinus palustris) forests.  

The results and analyses presented in this paper demonstrate the influence of extreme precipitation events, like hurricanes, on the hydrological behavior in forested watersheds and thus the transport of nutrients within and emanating out of the watershed. In addition, these results can help assess changes in the seasonal hydroperiod and biogeochemical processes in tidally mediated downstream riparian forests which are the estuary headwaters in this region. This study can assist with sustainable management and planning of water resource in low-gradient headwater watersheds in forested landscapes, such as the introduction of forest species more suitable to protection and conservation of water resources (e.g. restoration of long leaf pine (Pinus palustris)). However, multi-site studies on similar forest landscapes may be warranted to understand these complex seasonal ecosystem processes and their predictabilities in the face of climate change and sea level rise.