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Assessment of Hydrological Changes and Their Influence on the Aquatic Ecology over the last 58 Years in Ganjiang Basin, China

Sustainability 2019, 11(18), 4882; https://doi.org/10.3390/su11184882

by Yinghou Huang¹

, Binbin Huang¹, Tianling Qin^2,*

, Hanjiang Nie^2,3

, Jianwei Wang², Xing Li⁴ and Zhenqian Shen⁵

Reviewer 1: Anonymous

Reviewer 2: Anonymous

Reviewer 3: Anonymous

Reviewer 4:

Christina Papadaki

Sustainability 2019, 11(18), 4882; https://doi.org/10.3390/su11184882

Submission received: 3 July 2019 / Revised: 3 September 2019 / Accepted: 4 September 2019 / Published: 6 September 2019

Round 1

Reviewer 1 Report

The authors provide a useful examination of hydrologic change in the Ganjiang Basin using several statistical approaches. The paper's impact can be enhanced by more discussion of the reservoirs and aquatic life potentially impacted, not research just background information.

Specific comments:

59:”…runoff timing changes are caused by climate change and human activities.”

68: Remove “considering various related water supply objectives”

82: “…to assess hydrological changes and to understand..”

113: How much of the basin is upstream of the Waizhou station?

118: Remove –“There are many reservoirs in the basin.”

“In 2009, 3,959 reservoirs of various types existed in the basin, including 13 large, 118 medium and 3,828 small reservoirs.” Of these how many are hydropower? How many are on the main stem or main tributaries? If the latter information is not readily available ok.

120: What is the size definition of the large, medium and small.

149: Remove 1997

196: The language around the abrupt change point or abrupt point is not consistent, since it is a defined variable make sure to use the exact same wording, see line 25 and 96.

289 and 292: “… was the greatest of the three stations”

306, 311, 316 and 320: reference style is not followed. More examples after these lines of same issue.

318: When was the fill period for the Wan’an reservoir, you have completion date, but that is not the same? There are two other reservoirs completed in 1990, do they affect all three stations?

345: What are some of the migrating aquatic organisms. Is there a measure of the aquatic health change that can be cited?

355: What is the hydropower generation capacity in the basin?

370: Given that runoff and precipitation changes the same, what leads you to conclude from this that “It shows that precipitation has a great influence on annual runoff, and human activities made the annual runoff distribution process more uniform.”? This line needs clarification to bring it into agreement with the discussion section line 307-310.

384: provide an example measure of how the lower basin changed less than the upper and middle.

391: Joint reservoir management of course makes sense. Is there any insight here that can be provided, about how individually or collectively they are managed today?

Author Response

Dear Reviewer:

Thank you very much for your careful work. Your valuable comments for the article make it more complete, and it also benefit me a lot. The following are the details of the revision of the article:

Reviewer's general comments:

Reviewer's comments:

1.59:”…runoff timing changes are caused by climate change and human activities.”

Reply or modification:

I have made changes on page 2, line 61 :“Runoff is the key driving factor of the river ecosystem, runoff timing changes are caused by climate change and human activities.”

Reviewer's comments:

2.68: Remove “considering various related water supply objectives”

Reply or modification:

I have made changes on page 2, line 75.

Reviewer's comments:

82: “…to assess hydrological changes and to understand..”

Reply or modification:

I have made changes on page3, line 88 : “All of those studies suggest that IHA can be used to assess hydrological changes and to understand the interaction between flow and river ecosystems.”

Reviewer's comments:

113: How much of the basin is upstream of the Waizhou station?

Reply or modification:

I have made changes on page 3, line 124. “The water collection area of Waizhou Hydrology Station is 80,948km2”.

Reviewer's comments:

118: Remove –“There are many reservoirs in the basin.”

Reply or modification:

I have made changes on page 3, line 129 . and the latter information is difficult to obtain.

Reviewer's comments:

120: What is the size definition of the large, medium and small.

Reply or modification:

I have made changes on page 3, line131 . “Large reservoir: total reservoir capacity is more than 100 million m³; medium reservoir: total reservoir capacity is more than 10 million m³; small reservoir: total reservoir capacity is more than 100,000 m³”.

Reviewer's comments:

149: Remove 1997

Reply or modification:

I have made changes on page 6, line196 .

Reviewer's comments:

196: The language around the abrupt change point or abrupt point is not consistent, since it is a defined variable make sure to use the exact same wording, see line 25 and 96.

Reply or modification:

I have made changes on page 10, line 258,Change “abrupt point” to “abrupt change time”.

Reviewer's comments:

289 and 292: “… was the greatest of the three stations

Reply or modification:

I have made changes on page 21, line 375.

Reviewer's comments:

306, 311, 316 and 320: reference style is not followed. More examples after these lines of same issue.

Reply or modification:

I have made changes on page 22, line 391, 401, 400 and 410.

Reviewer's comments:

318: When was the fill period for the Wan’an reservoir, you have completion date, but that is not the same? There are two other reservoirs completed in 1990, do they affect all three stations?

Reply or modification:

I have made changes on page 22, line 407 :“especially the Wan'an Reservoir built in 1990 ,and fill period was 24 August 1990”.

Wan'an Reservoir is located in the upstream of three hydrological stations, while the other two reservoirs are located in the upstream of Wan'an Reservoir. The total storage capacity of Wan'an Reservoir is 20 times that of the other two reservoirs. Therefore, under the regulation of Wan'an Reservoir, the impact of the other two reservoirs on the downstream three hydrological stations can be neglected.

Reviewer's comments:

345: What are some of the migrating aquatic organisms. Is there a measure of the aquatic health change that can be cited?

Reply or modification:

I have made changes on page 6, line222 . The impact on ecosystems was added to Table 1.

Table 1. Summary of IHA parameters and ecological implications (Richter et al., 1996).

Statistics group	Hydrologic parameters	Ecosystem influences
Group 1: Magnitude of monthly water conditions	Mean value for each calendar month	Habitat availability for aquatic organisms Soil moisture availability for plants Availability of water for terrestrial animals
Group 2: Magnitude and duration of annual extreme water conditions	Annual minima 1-day means Annual maxima 1-day means Annual minima 3-day means Annual maxima 3-day means Annual minima 7-day means Annual maxima 7-day means Annual minima 30-day means Annual maxima 30-day means Annual minima 90-day means Annual maxima 90-day means	Balance of competitive, ruderal and stress tolerant organisms Creation of sites for plant colonization Structuring of aquatic ecosystems by abiotic vs. biotic factors Structuring of river channel morphology and physical habitat conditions
Group 3 Timing of annual extreme water conditions	Julian date of each annual 1-day maximum Julian date of each annual 1-day minimum	Compatibility with life cycles of organisms Predictability/avoidability of stress for organisms Access to special habitats during reproduction or to avoid predation
Group 4: Frequency and duration of high and low pulses	No. of high pulses each year No. of low pulses each year Mean duration of high pulses within each year Mean duration of low pulses within each year	Frequency and magnitude of soil moisture stress for plans Frequency and duration of anaerobic stress for plans Availability of floodplain habitats for aquatic organisms Nutrient and organic matter exchanges between river and floodplain
Group 5: Rate and frequency of water condition changes	Means of all positive differences between consecutive daily means Means of all negative differences between consecutive daily means No. of rises No. of falls	Drought stress on plans Entrapment of organisms on islands, flood plains Desiccation stress on low mobility stream edge (varial zone) organisms

I have made changes on page 23, line 438: “Reduced high pulses count and duration lead to fewer spawning areas in available habitats, and dams also hinder the migration of aquatic organisms such as fish（Wang,2015）.”

I have made changes on page 23, line 441: “Flow fluctuations have led to a decline in natural diversity and abundance of many native fish and invertebrates（Poff et al，1997；Poff and Zimmerman，2010）. comparative study on the ecology of Ganjiang River Basin before and after the completion of Wan'an Reservoir(Tian,1989；Jiao et al,2011；Huang et al,2014). It was found that the biodiversity of ecosystem in Ganjiang River Basin decreased significantly, especially the fish spawning grounds suffered serious damage. Tian 1982-1983 Sampling in Ganjiang River Basin (Tian , 1989): 118 species, 8 phyla and 63 genera of phytoplankton in Ganjiang River Basin; 125 Species of Zooplankton; 20 species of benthic organisms; 118 species of fish belonging to 74 genera, 22 families and 11 orders. After the water storage in Wan'an Reservoir, Jiao et al 2007-2009 Sampling in Ganjiang River Basin (Jiao et al, 2011): 47 species, 8 phyla and 30 genera of phytoplankton in Ganjiang River Basin; 25 Species of Zooplankton; 9 species of benthic organisms; 71 species of fish belonging to 58 genera, 16 families and 11 orders. The impact of the construction of water conservancy projects on aquatic organisms is mainly reflected in the fish resources. Huang compared the spawning grounds of five fishes in Ganjiang River before and after the construction of Wan'an Reservoir, and found that two of them had disappeared(Huang et al，2014).”

Reviewer's comments:

355: What is the hydropower generation capacity in the basin?

Reply or modification:

I have made changes on page 24, line 462 . “Ganjiang River Basin has developed an installed capacity of 1.577 million kw.”

Reviewer's comments:

Reply or modification:

I have made changes on page 22, line 394 : “Liu et al quantifications of climate and human activities on the runoff in the Ganjiang River Basin indicate that precipitation is the main cause of interannual variation in runoff; Reservoir construction significantly affects the seasonal distribution of runoff, resulting in a significant reduction in runoff during the wet season and a significant increase in runoff during the dry season(Liu,2016).”

I have made changes on page 25, line 486: “The annual runoff increases with the annual precipitation, but decreases with the increase of precipitation in wet season.”

Reviewer's comments:

384: provide an example measure of how the lower basin changed less than the upper and middle.

Reply or modification:

I have made changes on page 23, line 432 . “The influence of the upstream reservoir decreases as the downstream distance decreases(Lin et al,2017).”

Reviewer's comments:

391: Joint reservoir management of course makes sense. Is there any insight here that can be provided, about how individually or collectively they are managed today?

Reply or modification:

I have made changes on page 23, line 466: “The current reservoir operation mode in Ganjiang River Basin mainly focuses on the comprehensive utilization benefits such as flood control, power generation and shipping, and the reservoir operation generally does not consider the ecological function. The best choice for downstream flow management of reservoirs is to simulate natural conditions as much as possible（Gao et al，2012）. The main challenge facing reservoir management is to determine acceptable levels of change without compromising ecological health and ecosystem services. In the joint operation of reservoirs, the objective is to maximize the generation capacity of reservoirs, minimize the regional water shortage and minimize the deviation between flow and natural flow after the operation of each control section.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and suggestions for authors

General comments:

The topic of the paper is very interesting, within the scope of the journal, and worthy of investigation. However, I suggest that authors should take into consideration the following comments before the manuscript can be published in Sustainability.

Introduction:

The introduction can be extended so that more reference works can be mentioned. Currently, the length of this part of the manuscript is comparable with the abstract length. I suggest to add at the beginning of the introduction some information about the impact of sealing degree of the surface on the runoff. Authors can find some information in:

Starzec, M.; Dziopak, J.; Słyś, D.; Pochwat, K.; Kordana, S. Dimensioning of Required Volumes of Interconnected Detention Tanks Taking into Account the Direction and Speed of Rain Movement. Water 2018, 10, 1826. https://doi.org/10.3390/w10121826

Starzec, M. A critical evaluation of the methods for the determination of required volumes for detention tank. E3S Web Conf. 2018, 45, 00088. https://doi.org/10.1051/e3sconf/20184500088

Materials and Methods:

p. 3, line 106 – “2” should be written in superscript (km2)

p. 3, line 107 – Please remove the dot after the word “Figure”

p. 3, line 114 – “3” should be written in superscript (m3)

p.3 – Authors probably used two different styles of the text. The text in parts 2.2-2.3 has more leading than previous paragraphs.

p.5 line 148 – Please remove the word “below”

p.5 line 161 – Please add the number of Eq. in the sentence

Table 1 – Please add references

Figs. 2-4 – Please add axes descriptions

I also suggest to remove years from these paragraphs or add them in the sentences (not in brackets).

Results:

A few sentences should be added at the beginning of the part 3.1 to familiarize the reader with the content of this section. Also, Figures 2 and 3 should be cited in this text, not after Figures.

Moreover, Figure 4 and Table 2 should be moved.

Where is Table 3?

Fig. 5, 6 – Please add horizontal axes descriptions

Table 4-6 – L, M and H should be described

Table 6 should be moved to part 3.2.3

Fig. 7 – Please add axes descriptions

Discussion:

Two styles of references? Please remove names and years.

p. 15, line 313, p.16, line 338 – Please remove the dot after the word “Figure”

Figure 8 should be described more precisely. For example, the Figure shows that between 1964-1974 the coverage was equal to 0%. Really?

Table 7 – fonts??

p.17, line 395 – Remove the text “6. Patent”

Reference [25] – Maybe Richter?

Reference [32] – Add some description

Author Response

Dear Reviewer:

Thank you very much for your careful work. Your valuable comments for the article make it more complete, and it also benefit me a lot. The following are the details of the revision of the article:

Reviewer's general comments:

Reviewer's comments:

Starzec, M.; Dziopak, J.; Słyś, D.; Pochwat, K.; Kordana, S. Dimensioning of Required Volumes of Interconnected Detention Tanks Taking into Account the Direction and Speed of Rain Movement. Water 2018, 10, 1826. https://doi.org/10.3390/w10121826

Starzec, M. A critical evaluation of the methods for the determination of required volumes for detention tank. E3S Web Conf. 2018, 45, 00088. https://doi.org/10.1051/e3sconf/20184500088

Reply or modification:

I have made changes on page 2, line 63,“At the same time, the size of the surface drainage facilities and the construction of the reservoir have a significant impact on the runoff（Starzec ，2018；Starzec et al，2018；Shan et al，2019）.”

Reviewer's comments:

p. 3, line 106 – “2” should be written in superscript (km2)

Reply or modification:

I have made changes on page 3, line 125.

Reviewer's comments:

p. 3, line 107 – Please remove the dot after the word “Figure”

Reply or modification:

I have made changes on page 4, line 146.

Reviewer's comments:

p. 3, line 114 – “3” should be written in superscript (m3)

Reply or modification:

I have made changes on page 3, line 126.

Reviewer's comments:

p.3 – Authors probably used two different styles of the text. The text in parts 2.2-2.3 has more leading than previous paragraphs.

Reply or modification:

I have made changes on page 4, line 137.

Reviewer's comments:

p.5 line 148 – Please remove the word “below”

Reply or modification:

I have made changes on page 6, line 195.

Reviewer's comments:

p.5 line 161 – Please add the number of Eq. in the sentence

Reply or modification:

I have made changes on page 6, line 211.

Reviewer's comments:

8.Table 1 – Please add references

Reply or modification:

I have made changes on page 6, line 222.

Reviewer's comments:

Figs. 2-4 – Please add axes descriptions

Reply or modification:

I have made changes on page 10, line 265, line 268 and line 288.

Reviewer's comments:

I also suggest to remove years from these paragraphs or add them in the sentences (not in brackets).

Reply or modification:

I have made changes on page 6, line 192, line 196.

Reviewer's comments:

A few sentences should be added at the beginning of the part 3.1 to familiarize the reader with the content of this section. Also, Figures 2 and 3 should be cited in this text, not after Figures.

Reply or modification:

I have made changes on page 8, line 227: “Durbin-Watson test was used to test the autocorrelation of hydro-meteorological data. Based on the absence of autocorrelation in the data series, the trend of annual precipitation and flood season precipitation in Ganjiang River Basin and annual runoff and flood season runoff in three typical sections were analyzed by Mann-Kendall test. Sliding t-Test was used to determine the abrupt change points of three typical cross-section flow series.”

Reviewer's comments:

Moreover, Figure 4 and Table 2 should be moved.

Reply or modification:

I have made changes on page 12, line 289 and 291.

Reviewer's comments:

Where is Table 3?

Reply or modification:

I have made changes on page 12, line 291.

Reviewer's comments:

Fig. 5, 6 – Please add horizontal axes descriptions

Reply or modification:

I have made changes on page 14, line 320 and page16 line 347.

Reviewer's comments:

Table 4-6 – L, M and H should be described

Reply or modification:

I have made changes on page 14, line 322, page 16,line 350 and page 20,line 365 “L represents little or no change, M represents moderate change, H represents height change.”

Reviewer's comments:

Table 6 should be moved to part 3.2.3

Reply or modification:

I have made changes on page 20,line 365.

Reviewer's comments:

Fig. 7 – Please add axes descriptions

Reply or modification:

I have made changes on page 22, line 383.

Reviewer's comments:

Two styles of references? Please remove names and years.

Reply or modification:

I have made changes on page 22, line 391-410.

Reviewer's comments:

p. 15, line 313, p.16, line 338 – Please remove the dot after the word “Figure”

Reply or modification:

I have made changes on page 22, line 402, page 23, line 429.

Reviewer's comments:

Figure 8 should be described more precisely. For example, the Figure shows that between 1964-1974 the coverage was equal to 0%. Really?

Reply or modification:

I have made changes on page 23, line 413: “Among them, data were lacking in 1965-1973, 1976, 1980-1982 and 1985-1987.”

Reviewer's comments:

Table 7 – fonts??

Reply or modification:

I have made changes on page 23, line 416.

Reviewer's comments:

p.17, line 395 – Remove the text “6. Patent”

Reply or modification:

I have made changes on page 25, line 512.

Reviewer's comments:

Reference [25] – Maybe Richter?

Reply or modification:

I have made changes on page 27, line 597.

Reviewer's comments:

Reference [32] – Add some description

Reply or modification:

I have made changes on page 27, line 615.

Reviewer 3 Report

At first, I would like to thank the Author for an interesting article and hard work. Below is a few comments, which I believe, can improve the work.

1. Keywords: please replace “M-K test” with “trend analysis”, “IHA” with “indicators of hydrological change” and “RVA” with “variability of hydro-meteorological indicators”.

2. Line 63: please replace “attention” with “attention”.

3. Please remove the empty space between line 63 and 64.

4. At the beginning of line 63 can be placed information that intensive impact of human activities in catchments, contributes to the degradation of their water ecological status, which reflected in reduced abundance and diversity of particular species of aquatic organism (Wałęga, A.; Młyński, D.; Kokoszka, R.; Miernik, W. Possibilities of Applying Hydrological Methods for Determining Environmental Flows in Select Catchments of the Upper Dunajec Basin. Pol. J. Environ. Stud., 2015, 24(6), 2663-2676.

5. In Introduction the novelty of conducted study should be clearly emphasized. Actually, lack is information about it.

6. Line 106: please use the superscript in “km2”.

7. Methodologies: The Mann-Kendall test was used to detect a monotonic trend in the hydro-meteorological series. It is well-known that the serial correlation has a significant impact on the results of trend detection methods like Mann-Kendall test. I believe that the random variables used in this paper can be independent (that is to say, they may be not self-correlated). However, the authors do not mention something about this hypothesis. I think that the authors should apply some statistical test to prove this hypothesis (maybe the Durbin-Watson test) and to make some comment on the matter. Or the Modified Mann-Kendall test can be used.

8. What was the level of significant for trend analysis?

9. Please describe in detail the Mann-Kendall test and Sliding T-test.

10. Line 145: please remove “(1996)”.

11. Line 149: please remove “(1997)”.

12. Line 161: please give the reference for formula (1).

13. The chapter Results should be started by initial analysis of hydro-meteorological data, which included the determination of descriptive statistics for analyzed random variable.

14. Please do not start the chapter “Trend and abrupt change analysis of precipitation and runoff” by the figure 2. At the first should be placed a sentences which described, what kind of information were included at figure.

15. Figure 2 and 3: please explain in legend: “UF” and “UB”.

16. The figure 2 (annual) shows that in period 2004-2015 the significant results were appeared. What the reason is?

17. Why for M-K test the significant level was 0.05 and for t-test the 0.01 level was assumed?

18. The figures 5 and 6 shows a clearly difference in IHA situation for pre-impact flows and post-impact flows. What the reason is?

19. Line 306: please remove “(Ye et al, 2013)”.

20. Line 311: please remove “(Guo et al, 2007; Ye et al, 2013)”.

21. Line 316: please remove: “(Mittal et al，2014；Fiorella et al ，2018；Li et al，2017)”.

22. Line 320: please remove: “(Fiorella et al，2017；Lin et al，2017)”.

23. Why the figure 8 shows 0% forest coverage in particular years?

24. Line 330: please remove “(Grill et al，2015；Saraiva Okello et al，2015)”.

25. Lines 332-333: please remove “(Kennedy et al, 332 2014；Chen et al，2015)”.

26. Line 335: please remove “(Renöfält et al，2010; Grill et al，2015；Ibraim et al，2015)”.

27. Line 341: please remove „(Ma et al，2014).

28. Line 342: please remove “(Richter et al, 2006)”.

29. Line 346: please remove “(Sinnathamby S，2017)”.

30. Line 350: please remove “(Xue et al, 2017)”.

31. Line 352: please remove “(Saraiva et al，2015)”.

32. Line 355: please remove “(2015)”.

33. Line 361: please remove “(Li, 2017)”.

34. Conclusion: please do not punctate the main scores.

35. References: please use the Italic for the journal name and bold the years.

Author Response

Dear Reviewer:
Thank you very much for your careful work. Your valuable comments for the article make it more complete, and it also benefit me a lot. The following are the details of the revision of the article:

Reviewer's general comments:
At first, I would like to thank the Author for an interesting article and hard work. Below is a few comments, which I believe, can improve the work.

Reviewer's comments:
1. Keywords: please replace “M-K test” with “trend analysis”, “IHA” with “indicators of hydrological change” and “RVA” with “variability of hydro-meteorological indicators”.

Reply or modification:
I have made changes on page 2, line 58.

Reviewer's comments:
2. Line 63: please replace “attention” with “attention”.

Reply or modification:
I have made changes on page 2, line 67 .

Reviewer's comments:
3. Please remove the empty space between line 64 and 65.

Reply or modification:
I have made changes on page 2 , line 67 and line 68 .

Reviewer's comments:
4. At the beginning of line 63 can be placed information that intensive impact of human activities in catchments, contributes to the degradation of their water ecological status, which reflected in reduced abundance and diversity of particular species of aquatic organism (Wałęga, A.; Młyński, D.; Kokoszka, R.; Miernik, W. Possibilities of Applying Hydrological Methods for Determining Environmental Flows in Select Catchments of the Upper Dunajec Basin. Pol. J. Environ. Stud., 2015, 24(6), 2663-2676.

Reply or modification:
I have made changes on page 2, line 68.

Reviewer's comments:
5. In Introduction the novelty of conducted study should be clearly emphasized. Actually, lack is information about it.

Reply or modification:
Many scholars have studied the impact of human activities and climate change on the hydrological situation of rivers. However, they usually study the impact of a dam on the hydrological situation of the lower reaches, and have not studied rivers with many reservoirs as a whole. I made some changes on page 3, line 93-98: “The study attempts to provide an idea for the study of the overall hydrological regime change in the river basin with numerous reservoirs. Several typical sections of the river basin are selected to calculate the hydrological regime changes before and after the impact period based on the abrupt change points of the long-sequence runoff process. The hydrological regime changes of the river basin is evaluated as a whole.”

Reviewer's comments:
6. Line 106: please use the superscript in “km2”.

Reply or modification:
I have made changes on page 3, line 125. .

Reviewer's comments:
7. Methodologies: The Mann-Kendall test was used to detect a monotonic trend in the hydro-meteorological series. It is well-known that the serial correlation has a significant impact on the results of trend detection methods like Mann-Kendall test. I believe that the random variables used in this paper can be independent (that is to say, they may be not self-correlated). However, the authors do not mention something about this hypothesis. I think that the authors should apply some statistical test to prove this hypothesis (maybe the Durbin-Watson test) and to make some comment on the matter. Or the Modified Mann-Kendall test can be used.

Reply or modification:
I made some changes on page 5, lines 154-155: “In the paper, the Durbin-Watson test is used to test the hydro-meteorological series of the Ganjiang River Basin.”
I made some changes on page 5, lines 159-164: “The Durbin–Watson test(D,W,1950) is frequently used to detect the existence of autocorrelation in the ri residuals after regression（Gergely，2009），The equation as：
d_w=(∑_(i=2)^N▒〖(r_i-r_(i-1))〗^2 )/(∑_1^N▒r_i^2 ) (1)
Durbin and Watson summarized the upper limit d_u and the lower limit d_l of d_w. If d_u≤d_w≤4-d_u, there is no autocorrelation in the original sequence; d_u and d_l can be obtained by looking up tables.”
Reviewer's comments:
8. What was the level of significant for trend analysis?

Reply or modification:
I made some changes on page 5, lines 180: “The significance level of trend analysis selected in this study was 0.05.”

Reviewer's comments:
9. Please describe in detail the Mann-Kendall test and Sliding T-test.

Reply or modification:
I made some changes on page 5, lines 165-190: “Mann-Kendall is a nonparametric statistical test method, For time series x with n sample sizes, an order sequence is created:
s_k=∑_(i=1)^k▒r_i (k=2,3,⋯,n) (2)
Where
r_i={█(+1 if x_i>x_j @0 otherwise)┤ (j=2,3,⋯,i) (3)
Under the assumption of random independence of time series, the statistic UF is defined:
UF_k=[s_k-E(s_k)]/√(Var(s_k)) (k=2,3,⋯,n) (4)
Where UF_1=0, E(s_k)，Var(s_k) are the mean and variance of the cumulative number. If x_1,x_2,⋯,x_n are independent and continuous, the calculation formula is as follows:
E(s_k )=(n(n+1))/4 (5)
Var(s_k )=(n(n-1)(2n+5))/72 (6)
Repeat the above process according to the time series x inverse order x_n,x_(n-1),⋯,x_1, and make UB_k=-UF_k, k=n,n-1,⋯,1. If the value of UF or UB is greater than 0, the sequence shows an upward trend, and if the value of UF or UB is less than 0, the sequence shows a downward trend. If |UF| or |UB| is larger than U_α, indicating a significant trend change in the sequence. U_0.05=1.96, U_0.01=2.898, The significance level of trend analysis selected in this study was 0.05.
Sliding t-Test is set to be a reference point in time series “x” with a sample size “n”. The two subsequences before and after the reference point were defined to be x1 and x2.
t=(X ̅_1-X ̅_2)/(s∙√(1/n_1 -1/n_2 )) (7)
Where
s=√((n_1 s_1^2+n_2 s_2^2)/(n_1+n_2-2)) (8)
n_1 and n_2 is the sample size of x1 and x2, separately ,usually n_1=n_2;X ̅_1 and X ̅_2 is the average of x1 and x2, separately; s_1^2 and s_2^2 is the variance of x1 and x2, separately. If |t_i | < t_α there is no significant difference between the two subsequence. Otherwise, there is an abrupt change at the reference point; t_0.05=1.96, t_0.01=2.898.”

Reviewer's comments:
10. Line 145: please remove “(1996)”.

Reply or modification:
I have made changes on page 6, line 192.

Reviewer's comments:
11. Line 149: please remove “(1997)”.

Reply or modification:
I have made changes on page 6, line 196.

Reviewer's comments:
12. Line 161: please give the reference for formula (1).

Reply or modification:
I have made changes on page 6, line 210.

Reviewer's comments:
13. The chapter Results should be started by initial analysis of hydro-meteorological data, which included the determination of descriptive statistics for analyzed random variable.

Reply or modification:
I have made changes on page 8, line 232-238: “The dw calculated by Durbin–Watson test satisfies d_u≤d_w≤4-d_u(Table 2), When the significance level is 0.05, the precipitation-runoff data series reject autocorrelation. Mann-Kendall test can be used to analyze the trend of precipitation and runoff in typical sections of Ganjiang River Basin.”
Table 2. Autocorrelation test results of precipitation and typical section data series in Ganjiang River Basin
Data sequence dw(Annual) dw(Wet season) du 4-du Results
Precipitation 2.150 2.094 1.614 2.386 Reject autocorrelation
Dongbei Staion 2.120 2.325 1.614 2.386 Reject autocorrelation
Ji’an Staion 2.129 2.379 1.599 2.401 Reject autocorrelation
Waizhou Staion 2.134 2.344 1.614 2.386 Reject autocorrelation

Reviewer's comments:
14. Please do not start the chapter “Trend and abrupt change analysis of precipitation and runoff” by the figure 2. At the first should be placed a sentences which described, what kind of information were included at figure.

Reply or modification:
I have made changes on page 8, line 227“Durbin-Watson test was used to test the autocorrelation of hydro-meteorological data. Based on the absence of autocorrelation in the data series, the trend of annual precipitation and flood season precipitation in Ganjiang River Basin and annual runoff and flood season runoff in three typical sections were analyzed by Mann-Kendall test. Sliding t-Test was used to determine the abrupt change points of three typical cross-section flow series.”
Reviewer's comments:
15. Figure 2 and 3: please explain in legend: “UF” and “UB”.

Reply or modification:
I have made changes on page 5, line 171 and line 176-181: “the statistic UF is defined:UF_k=[s_k-E(s_k)]/√(Var(s_k)) (k=2,3,⋯,n) ，Repeat the above process according to the time series x inverse order x_n,x_(n-1),⋯,x_1, and make UB_k=-UF_k, k=n,n-1,⋯,1. If the value of UF or UB is greater than 0, the sequence shows an upward trend, and if the value of UF or UB is less than 0, the sequence shows a downward trend. If |UF| or |UB| is larger than U_α, indicating a significant trend change in the sequence. U_0.05=1.96, U_0.01=2.898, The significance level of trend analysis selected in this study was 0.05.”
Reviewer's comments:
16. The figure 2 (annual) shows that in period 2004-2015 the significant results were appeared. What the reason is?

Reply or modification:
The main task of this study is to briefly analyze the causes of runoff change. Based on the abrupt change of runoff, the typical sections in the upper, middle and lower reaches of Ganjiang River Basin are divided into pre-impact period and post-impact period to evaluate the impact of reservoir construction on the hydrological situation and ecosystem of Ganjiang River Basin. Therefore, there is no in-depth study on the causes of climate change.

Reviewer's comments:
17. Why for M-K test the significant level was 0.05 and for t-test the 0.01 level was assumed?

Reply or modification:
The abrupt change time can not be found by M-K test, so t-test and 0.01 significance level of t-test are selected to determine the most significant abrupt change time.

Reviewer's comments:
18. The figures 5 and 6 shows a clearly difference in IHA situation for pre-impact flows and post-impact flows. What the reason is?

Reply or modification:
The reason is（on page 23, line 427-434）:“The reservoirs built in the Ganjiang River Basin in the 1980’s and 1990’s are basically located in the upper and middle reaches of the Ganjiang River Basin. The largest reservoir, Wan’an, is located in the upper reaches of Dongbei Station, 16 km apart（Figure. 1). The influence of Wan'an reservoir on hydrological regime can be reflected by Dongbei Station. The construction and operation of large reservoirs have great influence on river ecology. The influence of the upstream reservoir decreases as the downstream distance decreases.Dam operation directly changes the flow state，thereby changing the river ecosystem.”

Reviewer's comments:
19. Line 307: please remove “(Ye et al, 2013)”.

Reply or modification:
I have made changes on page 22, line 391.

Reviewer's comments:
20. Line 312: please remove “(Guo et al, 2007; Ye et al, 2013)”.

Reply or modification:
I have made changes on page 22, line 400.

Reviewer's comments:
21. Line 317: please remove: “(Mittal et al，2014；Fiorella et al ，2018；Li et al，2017)”.

Reply or modification:
I have made changes on page 22, line 405.

Reviewer's comments:
22. Line 320: please remove: “(Fiorella et al，2017；Lin et al，2017)”.

Reply or modification:
I have made changes on page 22, line 410.

Reviewer's comments:
23. Why the figure 8 shows 0% forest coverage in particular years?

Reply or modification:
I have made changes on page 23, line 413.

Reviewer's comments:
24. Line 330: please remove “(Grill et al，2015；Saraiva Okello et al，2015)”.

Reply or modification:
I have made changes on page 23, line 421.

Reviewer's comments:
25. Lines 332-333: please remove “(Kennedy et al, 332 2014；Chen et al，2015)”.

Reply or modification:
I have made changes on page 23, line 423.

Reviewer's comments:
26. Line 335: please remove “(Renöfält et al，2010; Grill et al，2015；Ibraim et al，2015)”.

Reply or modification:
I have made changes on page 23, line 426.

Reviewer's comments:
27. Line 341: please remove „(Ma et al，2014).

Reply or modification:
I have made changes on page 24, line 433.

Reviewer's comments:
28. Line 342: please remove “(Richter et al, 2006)”.

Reply or modification:
I have made changes on page 24, line 434.

Reviewer's comments:
29. Line 346: please remove “(Sinnathamby S，2017)”.

Reply or modification:
I have made changes on page 24, line 438.

Reviewer's comments:
30. Line 350: please remove “(Xue et al, 2017)”.

Reply or modification:
I have made changes on page 24, line 457.

Reviewer's comments:
31. Line 352: please remove “(Saraiva et al，2015)”.

Reply or modification:
I have made changes on page 24, line 459.

Reviewer's comments:
32. Line 355: please remove “(2015)”.

Reply or modification:
I have made changes on page 24, line 463.

Reviewer's comments:
33. Line 361: please remove “(Li, 2017)”.

Reply or modification:
I have made changes on page 24, line 477.

Reviewer's comments:
34. Conclusion: please do not punctate the main scores.

Reply or modification:
I have made changes on page 25, line 492 to line 498.

Reviewer's comments:
35. References: please use the Italic for the journal name and bold the years.

Reply or modification:
I have made changes on page 25, line 526 to page 29, line 663.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments for the Authors

Manuscript ID sustainability-554184-peer-review-v1

General comments:

The topic covered fully corresponds to the aims and scope of the Journal Sustainability. It is evident that a lot of efforts in are involved. The manuscript covers different aspects of research and water management. Although the manuscript has a lot of information and needs improvements regarding the ecological documentation. Results should start with analysis and not with figures. Figures should be improved.

Reviewer comments:

Line 70-87: Please move this part to discussion.

Line 104: Please delete "Introduction of the ".

Line 105: Please be more specific about your study area. Is it a basin or a sub basin? Please use the same term all throughout the manuscript.

Line 111-114: This sentence doesn’t make sense. “Ganjiang River runoff is replenished by precipitation”

Line 120-122: Please move this part to discussion: “Reservoir construction and afforestation may change the hydrological situation of 120 Ganjiang Basin. Human activities such as reservoir construction and afforestation may change 121 the hydrological situation in the Ganjiang” River Basin. Also replace situation with status.

Line 123: Please rename the subtitle: “Study data” to Data

Line 124-125: “The precipitation data used in the paper were derived from the daily precipitation data of 2000 meteorological stations in China”. This part is confusing. Since you used data only from the Ganjiang River Basin. Upper, middle and lower part of the river

Line 125 – 129: The actual observation data of 125 meteorological stations with continuous precipitation data and distributed in the Ganjiang 126 River Basin were selected as the basic data of the study. A total of 53 meteorological stations 127 were selected after screening and converting it into precipitation of the Ganjiang River Basin 128 by using Tyson polygon.

Line 131: “Upper, middle and lower reaches”. Please be more specific here.

Fig. 1 Change the river color so to be visible, and replace the “river” with hydrographic network.

Line 135: Please replace “Methodologies” with Methods.

Line 144: Please write all initials of IHA with capitals. Also place (IHA) after the “Indicators of hydrological alteration”.

Line 145-146: This is a comment. Please delete it: "and supported by The Nature 145 Conservancy (TNC)".

Line 145-148: Please rephrase the sentence “IHA statistical package, developed by Richter et al. [10] (1996) and supported by The Nature Conservancy (TNC), has five groups of 33 indicators, including quantity, time, frequency, delay and change rate, which are closely related to the changes of river ecosystems（Table 1 below).”

Indicators of Hydrologic Alteration (IHA) is a software program not a statistical package. Richter et al (1996) described a Method for Assessing Hydrologic Alteration. The software has been developed from by several scientists of The Nature Conservancy. Please be more careful when describing the literature.

Line 147: What do you mean with delay? Please add “of” after “change” and “the” after “to the changes of”.

Line 149-150: Please replace “established” with developed. Also delete “based on IHA”. This is confusing.

Line 150: Please delete “and as a management tool for rivers”.

Line 153-157: This sentence needs improvement. “The RVA target range for each hydrological parameter is usually based on the selected percentile level or a simple multiple of the standard deviation of the pre-impact flow scheme parameters. The management goal is not to have the river reach the target range every year; instead, it reaches the target range at the same frequency as the natural or pre-impact flow state.”. What do you mean on the selected percentile level? Please delete the management goal is not to have the river reach the target range every year.

Line 163: Please replace “formula”, with equation and place the number of the equation next to it.

Line 174: Perhaps you could delete Table1 and add more relevant information in the study area.

Figure 1. Should be improved. It is not very clear which is the study area.

Line 177: Results, please explain what UF and UB means in Fig. 2 and 3. Also you need to mention again which is the wet season.

Author Response

Dear Reviewer:

Thank you very much for your careful work. Your valuable comments for the article made it more complete, and it also benefited me a lot. I have studied your comments carefully and have made revision which I hope meet with approval. The following are the details of the revision of the article:

Reviewer's general comments:

Reviewer's comments:

Line 70-87: Please move this part to discussion.

Reply or modification:

Thanks very much for your kind work and consideration on publication of my paper, your comments are all valuable and very helpful for revising and improving it. The function of Line 70-87 is to introduce the method IHA for evaluating the hydrological status in this study, and propose the innovation of this research. The discussion part is mainly about the impact of reservoir construction on hydrological status and river ecosystem.

I have made changes on page 3, line 93-98:“The study attempts to provide an idea for the study of the overall hydrological status change in the river basin with numerous reservoirs. Several typical sections of the river basin are selected to calculate the hydrological status changes before and after the impact period based on the abrupt change points of the long-sequence runoff process. The hydrological status changes of the river basin is evaluated as a whole”.

Reviewer's comments:

Line 104: Please delete "Introduction of the".

Reply or modification:

I have made changes on page 3, line 115.

Reviewer's comments:

Line 105: Please be more specific about your study area. Is it a basin or a sub basin? Please use the same term all throughout the manuscript.

Reply or modification:

I have made changes on page 3, line 116-118: “The study area is Ganjiang River Basin which is the seventh largest tributary of Yangtze River. The Ganjiang River Basin covers an area of about 83500 km²and account for 51 % of the territory in Jiangxi Province in central China”.

Reviewer's comments:

Line 111-114: This sentence doesn’t make sense. “Ganjiang River runoff is replenished by precipitation”

Reply or modification:

I have made changes on page 3, line 127-132:“The precipitation in wet season (April-September) accounts for 78.6% of the total annual precipitation. Ganjiang River runoff is recharged by precipitation, and the characteristics of runoff correspond to those of precipitation. Waizhou Hydrological Station has a collection area of 80,948 km² and an average annual runoff of 68.6 billion m³，the wet season (April-September) runoff accounts for 72.3% of annual runoff”.

Reviewer's comments:

Reply or modification:

I have made changes on page 26, line 454-456: “Reservoir construction and afforestation may change the hydrological status of Ganjiang Basin. Human activities such as reservoir construction and afforestation may change the hydrological status in the Ganjiang River Basin”.

Reviewer's comments:

Line 123: Please rename the subtitle: “Study data” to Data.

Reply or modification:

I have made changes on page 4, line 146.

Reviewer's comments:

Line 125–129: The actual observation data of 125 meteorological stations with continuous precipitation data and distributed in the Ganjiang 126 River Basin were selected as the basic data of the study. A total of 53 meteorological stations 127 were selected after screening and converting it into precipitation of the Ganjiang River Basin 128 by using Tyson polygon.

Reply or modification:

Because 53 meteorological stations located in the Ganjiang River Basin belong to the data collection of 2000 national meteorological stations in China，The meteorological data of 53 meteorological stations used in this study are extracted from the data sets of 2000 meteorological stations in China.

I have made changes on page 4, line 147-150: “The precipitation data from 53 Meteorological stations located in the Ganjiang River Basin (Figure 1) were obtained from National Climate Centre of China Meteorological Administration (CMA). The period of record of 53 meteorological stations used in this study is 1959–2016”.

Reviewer's comments:

Line 131: “Upper, middle and lower reaches”. Please be more specific here.

Reply or modification:

I have made changes on page 4, line 157-159: “Dongbei Station is a typical section in the upper reaches of Ganjiang River Basin, Ji'an Station is a typical section in the middle reaches, and Waizhou Station is a typical section in the lower reaches (Figure 1)”.

Reviewer's comments:

Fig. 1 Change the river color so to be visible, and replace the “river” with hydrographic network. Figure 1. Should be improved. It is not very clear which is the study area.

Reply or modification:

I have made changes on page 5, line 161.

Figure 1. Ganjiang River Basin

Reviewer's comments:

Line 135: Please replace “Methodologies” with Methods.

Reply or modification:

I have made changes on page 6, line 164.

Reviewer's comments:

Line 144: Please write all initials of IHA with capitals. Also place (IHA) after the “Indicators of hydrological alteration”.

Reply or modification:

I have made changes on page 8, line 212: “Indicators Of Hydrological Alteration (IHA)” .

Reviewer's comments:

Line 145-146: This is a comment. Please delete it: "and supported by The Nature 145 Conservancy (TNC)".

Reply or modification:

I have made changes on page 12, line 291.

Reviewer's comments:

Line 145-148: Please the sentence “IHA statistical package, developed by Richter et al. [10] (1996) and supported by The Nature Conservancy (TNC), has five groups of 33 indicators, including quantity, time, frequency, delay and change rate, which are closely related to the changes of river ecosystems（Table 1 below).”

Line 147: What do you mean with delay? Please add “of” after “change” and “the” after “to the changes of”.

Reply or modification:

The “delay” means “duration” in the article.

I have made changes on page 8, line 213-218 : “Richter et al (1996) described a Method for Assessing Hydrologic Alteration(IHA)., has five groups of 33 indicators, including quantity, time, frequency, duration and change of rate, which are closely related to the changes of the river ecosystems（Table 1 )”.

Reviewer's comments:

Line 149-150: Please replace “established” with developed. Also delete “based on IHA”. This is confusing.

Reply or modification:

I have made changes on page 8,line 219.

Reviewer's comments:

Line 150: Please delete “and as a management tool for rivers”.

Reply or modification:

I have made changes on page 8, line 220.

Reviewer's comments:

Reply or modification:

The selected percentile level means IHA values fall in the target ranges (between 25th percentile value and 75th percentile value) during the post- periods.

I have made changes on page 8, line 223-226: “The RVA target range is IHA values fall in the ranges (usually between 25th percentile value and 75th percentile value) during the post- periods. it is to attain the targeted range at the same frequency as occurred in the natural or pre-impact flow state”.

Reviewer's comments:

Line 163: Please replace “formula”, with equation and place the number of the equation next to it.

Reply or modification:

I have made changes on page 8, line 236.

Reviewer's comments:

Line 174: Perhaps you could delete Table1 and add more relevant information in the study area.

Reply or modification:

Table 1 (page 8, line 248) details the IHA parameters and their associated ecological impacts, supporting the discussion of the influence of reservoir on hydrological regime and river ecology.

Table 1. Summary of IHA parameters and ecological implications (Richter et al,1996).

Statistics group	Hydrologic parameters	Ecosystem influences
Group 1: Magnitude of monthly water conditions	Mean value for each calendar month	Habitat availability for aquatic organisms Soil moisture availability for plants Availability of water for terrestrial animals
Group 2: Magnitude and duration of annual extreme water conditions	Annual minima 1-day means Annual maxima 1-day means Annual minima 3-day means Annual maxima 3-day means Annual minima 7-day means Annual maxima 7-day means Annual minima 30-day means Annual maxima 30-day means Annual minima 90-day means Annual maxima 90-day means	Balance of competitive, ruderal and stress tolerant organisms Creation of sites for plant colonization Structuring of aquatic ecosystems by abiotic vs. biotic factors Structuring of river channel morphology and physical habitat conditions
Group 3 Timing of annual extreme water conditions	Julian date of each annual 1-day maximum Julian date of each annual 1-day minimum	Compatibility with life cycles of organisms Predictability/avoidability of stress for organisms Access to special habitats during reproduction or to avoid predation
Group 4: Frequency and duration of high and low pulses	No. of high pulses each year No. of low pulses each year Mean duration of high pulses within each year Mean duration of low pulses within each year	Frequency and magnitude of soil moisture stress for plans Frequency and duration of anaerobic stress for plans Availability of floodplain habitats for aquatic organisms Nutrient and organic matter exchanges between river and floodplain
Group 5: Rate and frequency of water condition changes	Means of all positive differences between consecutive daily means Means of all negative differences between consecutive daily means No. of rises No. of falls	Drought stress on plans Entrapment of organisms on islands, flood plains Desiccation stress on low mobility stream edge (varial zone) organisms

I have made changes on page 3, line 121: “The average elevation is approximately 112 m above mean sea level”.

I have made changes on page 3, line 123-124: “The average elevation is approximately 112 m above mean sea level. The mean annual air temperature is around 17.8℃. The highest and lowest temperatures are 39.5℃ and -5.8℃”.

I have made changes on page 3, line 130: “Waizhou Hydrological Station has a collection area of 80,948 km²”.

Reviewer's comments:

Line 177: Results, please explain what UF and UB means in Fig. 2 and 3. Also you need to mention again which is the wet season.

Reply or modification:

I have made changes on page 7, line 186 and line 195-200: “the statistic UF is defined: ，Repeat the above process according to the time series x inverse order , and make , . If the value of UF or UB is greater than 0, the sequence shows an upward trend, and if the value of UF or UB is less than 0, the sequence shows a downward trend. If |UF| or |UB| is larger than , indicating a significant trend change in the sequence.,, The significance level of trend analysis selected in this study was 0.05.”

I have made changes on page 12, line 293 and line 296: “Wet season: April-September”.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The manuscript is an original contribution and the topic is of interest for the readership of the Sustainability journal.

The presentation is good.

Author Response

Thanks very much for your kind work and consideration on publication of my paper.

Reviewer 3 Report

The manuscript has been significantly improved following the recommendations
of the Reviewer. All my concerns have been addressed and convincingly justified. I will be happy to see an article, published in Sustainability.

Author Response

Thanks very much for your kind work and consideration on publication of my paper.

Reviewer 4 Report

Comments for the Authors

Manuscript ID sustainability-554184-peer-review-v2

Reply or modification:

Reviewer's comments:

I am sorry but the changes are not clear. There is no line 93-98 in the revised manuscript. Perhaps you refer to the old version. Please be specific about the changes that you have made based on the new version. I can see that this has been made all through the new version of the manuscript perhaps it is a numbering problem from the pdf extraction.

Reply or modification:

Reviewer's comments:

What do you mean with typical. Perhaps you are referring to a classification? Please provide a description or a reference.

Reply or modification:

I have made changes on page 5, line 161.

Figure 1. Ganjiang River Basin

Reviewer's comments:

Please correct the legend and replace the value with the correct name. I assume that this is altitude (m) from Digital Elevation model but you need to specify it and correct it in the legend. Also, you may need to correct the lowest value -6. It is not logical to have negative values inside the mainland.

Author Response

Dear Reviewer:

Reviewer's comments:

Reply or modification:

I am sorry about the previous operation. I guess line 93-98 corresponds to line 137-142 in the previous PDF version you see (Fig 1). The version uploaded this time corresponds to page 3, line 89-94.

Fig 1. contents corresponding to the previous PDF version

Reviewer's comments:

What do you mean with typical. Perhaps you are referring to a classification? Please provide a description or a reference.

Reply or modification:

I have made changes on page 4, line 153-160：Dongbei Station is the most upstream hydrological station of Ganjiang mainstream, located at 15 km downstream of Wan'an Reservoir, which can quantify the hydrological variability caused by Wan'an Reservoir. Ji'an Station is located in the middle reaches of Ganjiang River Basin. The downstream of Ji'an Station is Jishui Fish Spawning Ground[52]. The hydrological status changes of Ji'an Station can provide a basis for discussing the change of Aquatic ecology in Ganjiang River Basin. Waizhou Station is the most downstream hydrological station of Ganjiang River, which can reflect the hydrological status changes of Ganjiang River Basin as a whole.

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Assessment of Hydrological Changes and Their Influence on the Aquatic Ecology over the last 58 Years in Ganjiang Basin, China

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