Response of Agricultural Drought to Meteorological Drought: A Case Study of the Winter Wheat above the Bengbu Sluice in the Huaihe River Basin, China
Round 1
Reviewer 1 Report
General Comments: This study is mainly about the response of winter wheat drought to meteorological drought. The Crop Water Deficit Index (CWDI) and Relative Moisture Index (M) were used to monitor winter wheat drought and meteorological drought respectively. The lag time between CWDI and M was investigated for all growth stages of winter wheat crop using wavelet analysis and finally, the gery relation analysis was performed to analyze the relationship between the time lag of winter wheat drought and geographical factors. This study is interesting, but I have several concerns about this study. Major revision is necessary before final decision.
Major points:
- The introduction section need to be improved by citing recent articles related to drought propagation, for example, Exploring the influence of climate change-induced drought propagation on wetlands (Ecological Engineering, 149) and Investigating effect of climate change on drought propagation from meteorological to hydrological drought using multi-model ensemble projections (Stochastic Environmental Research and Risk Assessment, 34(1)).
- Authors mentioned several drought indices in the introduction section for calculating meteorological drought and agricultural drought. Why are authors not using most popular meteorological drought index SPI? Why did authors select CWDI and M in this analysis? These things should be clarified at least in the introduction section.
- The objectives of the study need to be clarified in the Introduction section.
- How authors calculate Time interval/d (Table 4) from the main oscillation. Main oscillation is clear from the figure 7. Please elaborate the relationship between main oscillation and Time interval.
- There are many bold outline areas in Figure 7 a,b,c,d. Each bold outlined area has arrows with different directions. Which bold outlined area have been selected and how authors measured the phase angle? Is this angle measured from time axes?
- Table 4. Does this time interval show that winter wheat drought lags behind meteorological drought? According to my understanding, in Pre-winter growth period winter wheat drought lags behind meteorological drought by 26.6 days. Why does this lag time differ in each growth stage?
- Line 323-324: With the change of growth period, the correlation between temperature and the time lag of winter wheat drought showed a downward trend.
- Line 343: Authors mentioned that "The sites with high correlation between time lag of winter wheat drought and precipitation were mostly distributed in the north of the central area with less precipitation" where as the precipitation in the southern area of basin is less as compared to rest of the basin. Then, why the correlation between lag time of winter wheat drought and precipitation is less in that area?
- Mann-Kendall test is not described in the methodology section. Just did trend analysis in Result section. It should be explained first.
- There are many wrong English expressions. The manuscript should be revised with aid of native speakers.
Minor points:
- Line 12: Abstract: Replace “investigate” with “investigated”.
- Line 91-94: Rewrite the sentence.
- Revise the Figure 1 and also show the Huaihe river in the Figure 1.
- Line 121: Authors described cumulative precipitation (P). Cumulative P for how many days?
- Line 312: What is this “aspect” factor in geographical factors?
- Line 373: Remove "it is" once
Author Response
Dear reviewer,
Thank you very much for providing comments. Your suggestions are helpful for improving the manuscript. In the following, we address all comments point-by-point.
Comment 1: The introduction section need to be improved by citing recent articles related to drought propagation, for example, Exploring the influence of climate change-induced drought propagation on wetlands (Ecological Engineering, 149) and Investigating effect of climate change on drought propagation from meteorological to hydrological drought using multi-model ensemble projections (Stochastic Environmental Research and Risk Assessment, 34(1)).
Answer:
Thank for your suggestion, we have cited these two references and another reference about the method of Mann-Kenddall as follows.
[16] Jehanzaib, M. & Kim, T.W. Exploring the influence of climate change-induced drought propagation on wetlands. Ecol. Eng. 2020, 149, 105799.
[36] Jehanzaib, M.; Sattar, M.N.; Lee, J.H. Investigating effect of climate change on drought propagation from meteorological to hydrological drought using multi-model ensemble projections. Stoch. Env. Res. Risk A. 2020, 34: 7-21.
[47] Atta-ur-Rahman & Dawood, M. Spatio-statistical analysis of temperature fluctuation using Mann–Kendall and Sen’s slope approach. Clim. Dyn. 2016, 48, 783-797.
[48] Jain, S. K. & Kumar, V. Trend analysis of rainfall and temperature data for India. Curr. Sci. 2012,102, 37–49.
Comment 2: Authors mentioned several drought indices in the introduction section for calculating meteorological drought and agricultural drought. Why are authors not using most popular meteorological drought index SPI? Why did authors select CWDI and M in this analysis? These things should be clarified at least in the introduction section.
Answer:
Relative moisture index (M) and standardized precipitation index (SPI) are important indicators for meteorological drought research, but the indicators selected in the calculation process are different. The standardized precipitation index (SPI) represents the probability of precipitation in a certain period of time, while the relative moisture index (M) analyzes the water balance of a certain period based on precipitation, evapotranspiration, etc. Therefore, our research selected M indicator to compare and analyze the delay and spatial distribution difference of drought, which is of great significance of drought assessment and monitoring.
In addition, we added the sentence as follow to explain why we selected CWDI and M (Page 2 line81-83).
“At present, the research on drought based on CWDI and M mainly analyzes the spatial and temporal distribution of drought with a single index, rarely involving the correlation and time lag of CWDI and M research. As CWDI is calculated in ten days, and M is applicable to the monitoring and assessment of drought in the scale above ten days of crop growth season, in order to ensure the relative consistency of scale, the calculation of M was also in ten days. Therefore, CWDI was used to examine winter wheat drought, and M was used to examine meteorological drought in this study.”
Comment 3: How authors calculate Time interval/d (Table 4) from the main oscillation. Main oscillation is clear from the figure 7. Please elaborate the relationship between main oscillation and Time interval.
Answer:
In fig. 7, we can easily get the main oscillation. For example fig.7 a, you can get the main oscillation is 2.06～3.90/a. The time interval of CWDI and M can be got by calculating the phase angle corresponding to the main oscillation period in MATLAB. In order to understand easily, we added the sentence as follow to describe it. (Page10., line319-320).
“The time interval of CWDI and M can be got by calculating the phase angle corresponding to the main oscillation period in MATLAB.”
Figure 7. Time-frequency domain characteristics of cross-wavelet transform of CWDI and M in four growth periods of winter wheat (pre-winter growth period a, over-wintering period b, greening and heading period c, filling and mature period d).
Comment 4: There are many bold outline areas in Figure 7 a,b,c,d. Each bold outlined area has arrows with different directions. Which bold outlined area have been selected and how authors measured the phase angle? Is this angle measured from time axes?
Answer:
Same answer as above question, you should get the main oscillation, specific values can be calculated on MATLAB. The main oscillation period can be obtained through wavelet square result, although there are several bold outline areas in Fig7.
Comment 5: Table 4. Does this time interval show that winter wheat drought lags behind meteorological drought? According to my understanding, in Pre-winter growth period winter wheat drought lags behind meteorological drought by 26.6 days. Why does this lag time differ in each growth stage? While the shortest time lag was observed during the greening and heading period, longest was seen during the over-wintering period.
Answer:
We made the clear description at the beginning of the 4.2.2 (Time lag for meteorological drought to winter wheat drought). (Page10, line 304-307)
“There are several reasons for lag time differing in each growth stage: (1) Growth characteristics of winter wheat drought. Drought-tolerance of winter wheat in a different stage of growth is different. (2) The influence of climate factors. Differences in the lag time for meteorological drought are related to the condition of precipitation and temperature in the different growth period.”
Comment 6: Line 323-324: With the change of growth period, the correlation between temperature and the time lag of winter wheat drought showed a downward trend.
Line 343: Authors mentioned that "The sites with high correlation between time lag of winter wheat drought and precipitation were mostly distributed in the north of the central area with less precipitation" where as the precipitation in the southern area of basin is less as compared to rest of the basin. Then, why the correlation between lag time of winter wheat drought and precipitation is less in that area?
Answer:
The groundwater resources and waterways in southern area of basin are abundant. The lag time of winter wheat drought is affected not only by precipitation, but also impacted by rich groundwater resources. The sites with low correlation between time lag of winter wheat drought and precipitation were mostly distributed in the southern area.
Comment 7: Mann-Kendall test is not described in the methodology section. Just did trend analysis in Result section. It should be explained first.
Answer:
We added a description of chapter 3.2.6 for it (Page7, line209-213).
3.2.6. Mann-Kendall test
The statistical significance of the trend in monthly and annual series was analyzed by applying the non-parametric Mann-Kendall (MK) test. The MK test has been widely used in meteorological time series data, such as temperature [47] and precipitation [48]. The test validates the null hypothesis of no trend, assuming that there is an increased or decreased trend.
[47] Atta-ur-Rahman & Dawood, M. Spatio-statistical analysis of temperature fluctuation using Mann–Kendall and Sen’s slope approach. Clim. Dyn. 2016, 48, 783-797.
[48] Jain, S. K. & Kumar, V. Trend analysis of rainfall and temperature data for India. Curr. Sci. 2012,102, 37–49.
Technical Corrections
Line 12: Abstract: Replace “investigate” with “investigated”.
Line 91-94: Rewrite the sentence.
Revise the Figure 1 and also show the Huaihe river in the Figure 1.
Line 121: Authors described cumulative precipitation (P). Cumulative P for how many days?
Line 312: What is this “aspect” factor in geographical factors?
Line 373: Remove "it is" once
Answer:
- We rewritten the sentence “This study investigated the winter wheat in response to occurring droughts for the region above the Bengbu Sluice in the Huaihe River from 1961-2015 based on the daily scale dataset of 60 meteorological stations.” (Page1, line 12-14)
- “The sutdy area is located above the Bengbu Sluice in the Huaihe River Basin, and the total area is about 121,000 km2 (Figure 1). The terrain of the study area is complex. The annual mean temperature ranges from 12.1 to 15.8°C, and the mean yearly precipitation is about 861mm.” (Page3, line 95-97)
3.
Figure 1 Locations of the study area and meteorological stations.
- “Where P is the cumulative precipitation for 10 days”. (Page4, line 138)
- This “aspect” values indicate the directions the physical slopes face.
- “and it is extremely difficult to consider the mutual feedback mechanism between them.”
Author Response File: 
Author Response.pdf
Reviewer 2 Report
WATER: review of the paper water-903551
“Response of Agricultural Drought to Meteorological Drought—A case study of the Winter Wheat Above the Bengbu Sluice in the Huaihe River Basin, China”
English has various spelling, grammar and style errors, and the authors have to revise it accurately. In the following a few errors among many others:
LINE 12
Text
“In this study, we investigate the winter wheat in response to occurring droughts for the region above the Bengbu Sluice in the Huaihe River from 1961-2015 based on the daily scale dataset of 60 meteorological stations.”
Comment
The style of this sentence is quite twisted. Better is “This study investigates the winter wheat in response to occurring droughts for the region above the Bengbu Sluice in the Huaihe River from 1961-2015 based on the daily scale dataset of 60 meteorological stations.”
LINE 44
Text
“Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, including such as precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, and reduced groundwater or reservoir levels [11].”
Comment
“such as” should be deleted.
LINE 49
Text
“For meteorological drought, it is usually investigated using the percentage of precipitation anomalies (Pa) [12,13], standardized precipitation index (SPI) [14,15], relative moisture index (M) [16,7], palmer drought severity index (PDSI) [17,18], or comprehensive meteorological drought index (CI) etc.[19,20]. For agricultural drought, it is usually investigated using the ….. etc etc..”
Comment
Here it seems to me that there are two grammatical errors; I believe that the sentence should be "The meteorological drought is usually investigated using the percentage of precipitation anomalies (Pa) [12,13], standardized precipitation index (SPI) [14,15], relative moisture index (M) [16,7], palmer drought severity index (PDSI) [17,18], or comprehensive meteorological drought index (CI)etc.[19,20]. The agricultural drought is usually investigated using …… etc. etc.”
LINE 85
Text
“The area above the Bengbu Sluice in the Huaihe River Basin is selected as the study area, with an area of about 121,000 km2 (Figure 1). The terrain of the study area is complex. The annual mean temperature ranges from 12.1 to 15.8°C, and the annual mean precipitation is about 861mm. The interannual variation of precipitation is significant, which shows peak trend, and annual meanprecipitation shows the spatial distribution characteristics of high in the south and low in the north, which form typical regional drought and flood characteristics of “flooding under heavy rainfall, waterlogging under normal rainfall, and drought under no rainfall” [37,38,39]. Affected by special geographical location, climatic conditions and underlying surface, agricultural droughts and floods occur frequently in the study area from 1949 to the present, which is about once every 4 years, it is a typical area for agricultural drought and flood researches [22].”
Comment
This paragraph is difficult to read; the second part is almost incomprehensible (before 1949 there were no droughts?). The first sentence can be adjusted as follows: "The selected area is located above the Bengbu Sluice in the Huaihe River Basin; its size is about 121,000 km2 (Figure 1). The terrain of the study area is complex. The annual mean temperature ranges from 12.1 to 15.8°C, and the mean yearly precipitation is about 861mm”. I leave it to the authors to adjust the second sentence, and I end here the English correction, with the recommendation to have the paper reviewed by a translator.
LINE 35
Text:
“Under the climate change, droughts occur frequently, and agricultural production suffers severe economic losses [1,2].”
Comment
In general, this sentence is not correct, since climate change will increase average precipitation over large areas of the planet. The increase in droughts will not occur everywhere: it will occur mainly in areas already semi-arid today. In any case, the phrase, besides being incorrect, is superfluous and can be omitted.
General comments
The methods used by the authors appear, if not new, correct. Some in-depth analysis of temperature and precipitation trends would have made the article more interesting. A delicate point is the number of stations used for analysis. The density of rainfall stations is one station every 2000 km2, which is very low. I understand that the authors could only use the available data, but they must point out that the robustness of their results is weakened by the scarce data available. Why didn't the authors consider the geology of the basin among its characteristics? The types of rocks and their permeability affect both the characteristics of the surface soils and the number of water springs andthe regime of the rivers. Probably, if in the final correlations the authors had also considered groundwater levels (where available) very high correlations would have been found. Finally, in the conclusions the reader would like to read some considerations that go beyond the mere description of what happens: is it possible to exploit these results to minimize the impact of drought (area forgroundwater exploitation, construction of reservoirs in appropriate areas of the basin, etc.)? A brief discussion on these aspects would make the article a little more interesting.
I believe that the article deserves to be published after the authors have properly considered all the above considerations.
Comments for author File: Comments.pdf
Author Response
Dear reviewer,
Thank you very much for providing comments. Your suggestions are helpful for improving the manuscript. In the following, we address all comments point-by-point.
Comment 1: “In this study, we investigate the winter wheat in response to occurring droughts for the region above the Bengbu Sluice in the Huaihe River from 1961-2015 based on the daily scale dataset of 60 meteorological stations.” The style of this sentence is quite twisted.
Answer:
We have revised this sentence into “This study investigated the responses of winter wheat to drought for the above part of Bengbu Sluice in the Huaihe River based on the daily scale dataset of 60 meteorological stations from 1961-2015”. Please see Lines 12-14.
Comment 2: “Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, including such as precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, and reduced groundwater or reservoir levels [11].” “such as” should be deleted.
Answer:
We have deleted the term of “such as” in this sentence. Please see Line 49.
Comment 3: “For meteorological drought, it is usually investigated using the percentage of precipitation anomalies (Pa) [12,13], standardized precipitation index (SPI) [14,15], relative moisture index (M) [16,7], palmer drought severity index (PDSI) [17,18], or comprehensive meteorological drought index (CI) etc.[19,20]. For agricultural drought, it is usually investigated using the ….. etc etc..” Here it seems to me that there are two grammatical errors
Answer:
We have revised this sentence into “The meteorological drought is usually investigated with the percentage of precipitation anomalies (Pa) [12,13], standardized precipitation index (SPI) [14,15,16], relative moisture index (M) [7,17], palmer drought severity index (PDSI) [18,19], and comprehensive meteorological drought index (CI) [20,21], etc. Please see Lines 52-55.
Comment 4: “The area above the Bengbu Sluice in the Huaihe River Basin is selected as the study area, with an area of about 121,000 km2 (Figure 1). The terrain of the study area is complex. The annual mean temperature ranges from 12.1 to 15.8°C, and the annual mean precipitation is about 861mm. The interannual variation of precipitation is significant, which shows peak trend, and annual mean precipitation shows the spatial distribution characteristics of high in the south and low in the north, which form typical regional drought and flood characteristics of “flooding under heavy rainfall, waterlogging under normal rainfall, and drought under no rainfall” [37,38,39]. Affected by special geographical location, climatic conditions and underlying surface, agricultural droughts and floods occur frequently in the study area from 1949 to the present, which is about once every 4 years, it is a typical area for agricultural drought and flood researches [22].” This paragraph is difficult to read; the second part is almost incomprehensible (before 1949 there were no droughts?).
Comment 5: The interannual variation of precipitation is significant, which shows peak trend, and annual mean precipitation shows the spatial distribution characteristics of high in the south and low in the north, which form typical regional drought and flood characteristics of “flooding under heavy rainfall, waterlogging under normal rainfall, and drought under no rainfall” [37,38,39]. Agricultural droughts and floods occur once every four years in the study area from 1949 to the present, which is caused by special geographical location, climatic conditions and underlying surface [22].
Answer:
According to the opinions of reviewers, we improved and revised the sentence accurately. Please see Lines 94-107.
Comment 6: “Under the climate change, droughts occur frequently, and agricultural production suffers severe economic losses [1,2].” In general, this sentence is not correct, since climate change will increase average precipitation over large areas of the planet. The increase in droughts will not occur everywhere: it will occur mainly in areas already semi-arid today. In any case, the phrase, besides being incorrect, is superfluous and can be omitted.
Answer:
As suggested by the reviewer, there is the problem of poor effectiveness of expression in this sentence. We changed the form of this sentence, and it expressed in more detailed.
“Under the climate change, agricultural losses caused by drought have become more and more severe.” Please see Lines 37-38.
Comment 7: The methods used by the authors appear, if not new, correct.
Some in-depth analysis of temperature and precipitation trends would have made the article more interesting. A delicate point is the number of stations used for analysis. The density of rainfall stations is one station every 2000 km2, which is very low. I understand that the authors could only use the available data, but they must point out that the robustness of their results is weakened by the scarce data available. Why didn't the authors consider the geology of the basin among its characteristics? The types of rocks and their permeability affect both the characteristics of the surface soils and the number of water springs and the regime of the rivers. Probably, if in the final correlations the authors had also considered groundwater levels (where available) very high correlations would have been found.
Answer:
Consider the general comment, the groundwater levels have an impact on the lag time of drought.
We made the analysis of correlation between time lag of winter wheat drought and depth of shallow groundwater in this case. Also, we made a proper description at the 4.3.2 (Spatial distribution of grey relation between the time lag of winter wheat drought and geographical factors of underlying surface). The results show that the deeper depth is, the high time lag of drought is.
“The sites with high correlation between time lag of winter wheat drought and depth of shallow groundwater were mostly distributed in the northern and southern areas.” (Page13, line 379-381) Accordingly, we also added information about the depth of groundwater in the abstract (Page1, line 31), conclusions (Page15, line 442) and 4.3.1. (Page12, line 354)
Figure 9. The grey relation degree between different geographical factors of underlying surface and the time lag of winter wheat drought in the greening and heading period (Soil field capacity a, elevation b, slope c, aspect d, precipitation e, temperature f, depth of shallow groundwater g).
Note: The closer grey relation to 1, the higher the correlation.
Figure 8. Grey relation between the time lag of winter wheat drought and each geographical factors of underlying surface in each growth period.
Comment 8: Finally, in the conclusions the reader would like to read some considerations that go beyond the mere description of what happens: is it possible to exploit these results to minimize the impact of drought (area for groundwater exploitation, construction of reservoirs in appropriate areas of the basin, etc.)? A brief discussion on these aspects would make the article a little more interesting.
Answer:
- We made the clear suggestions for minimizing the impact of drought at the end of the discussion. (Page15, line 415-419)
“(4) The suggestions for minimizing the impact of drought. appropriate measures are following below: a. Strengthening for the construction of water conservancy facilities, the establishment of agricultural irrigation in scientific way is necessary for the prevention of drought.
- Strengthening early warning systems of agricultural drought and set up response measures to ensure efficient control the drought.
- The scientific method for planting drought-resistant crops is worth of spreading in drought area.”
- Moreover, we put the short description for concluding the objective of calculation. (Page15, line 436-438)
“The calculation of response time lags for agricultural drought to meteorological drought could provide the foundation for the prevention measure of drought.”
Author Response File: 
Author Response.docx
Round 2
Reviewer 1 Report
Author’s made significant changes in the revised version of the manuscript. My decision is to accept the manuscript.
