El Ni&ntilde;o Southern Oscillation (ENSO)-induced hydrological anomalies in central Chile

van Dongen, Renee; Scherler, Dirk; Wendi, Dadiyorto; Deal, Eric; Mao, Luca; Marwan, Norbert; Meier, Claudio I.

doi:https://doi.org/10.5194/egusphere-2022-1234

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https://doi.org/10.5194/egusphere-2022-1234

Preprints

05 Dec 2022

| 05 Dec 2022

El Niño Southern Oscillation (ENSO)-induced hydrological anomalies in central Chile

Renee van Dongen, Dirk Scherler, Dadiyorto Wendi, Eric Deal, Luca Mao, Norbert Marwan, and Claudio I. Meier

Abstract. The El Niño Southern Oscillation (ENSO) is a major driver of climatic anomalies around the globe. How these climatic anomalies translate into hydrological anomalies is important for water resources management, but difficult to predict due to the non-linear relationship between precipitation and river discharge, and contrasts in hydrological response in regions with different hydrological regimes. In this study we investigate how ENSO-induced climatic anomalies translate into hydrological anomalies by focussing on Central Chile (29–42° S), a relatively small area affected by ENSO, that displays steep latitudinal and elevational climatic gradients. We analyse daily discharge timeseries from 178 discharge stations together with monthly temperature and precipitation data. Based on the Multivariate ENSO Index (MEI) we classified the discharge data for the time period 1961–2009 into El Niño (MEI>0.5), La Niña (MEI<-0.5) and non-ENSO periods (˗0.5>MEI<0.5), and calculated relative differences in mean monthly temperature, precipitation, and discharge, as compared to non-ENSO conditions. The results reveal that precipitation and specific discharge generally increase during El Niño events, while they decrease during La Niña events. However, there exist large spatial and seasonal variations. The mean monthly precipitation and specific discharge anomalies during both the El Niño and the La Niña phases are strongest in the semi-arid region (29-32° S), followed by the mediterranean (32°–36° S) and humid-temperate (36°–42° S) regions. During El Niño events, the semi-arid and mediterranean regions experience mean monthly specific discharge increases of up to +396.5 % and +104.5 %, respectively, and a considerable increase in the frequency and magnitude of high flows. In contrast, discharge in the humid-temperate region is most sensitive to rainfall deficits during La Niña events, as revealed by an increased frequency of low flows. We find that the different hydrological regimes (rainfall- or snow-dominated) show large contrasts in how ENSO-induced climatic anomalies are translated into hydrological anomalies, in that snowmelt induces a delayed discharge peak during El Niño, provides a minimum streamflow during dry La Niña conditions, and reduces the discharge variability in rivers. Finally, we discuss the implications for water resources management, highlighting the need for different ENSO prediction and mitigation strategies in central Chile, according to catchment hydrological regime.

Received: 08 Nov 2022 – Discussion started: 05 Dec 2022

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.

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Renee van Dongen, Dirk Scherler, Dadiyorto Wendi, Eric Deal, Luca Mao, Norbert Marwan, and Claudio I. Meier

Status: closed

CC1:
'Comment on egusphere-2022-1234', Cristian Chadwick, 18 Jan 2023

Title: El Niño Southern Oscillation (ENSO)-induced hydrological anomalies in central Chile
Summary:
This paper presents a well written comprehensive work, related to the El Niño Southern Oscillation (ENSO) anomalies. In particular, there is a presentation of how the different phases of the ENSO affect the hydrological conditions in Central Chile (29-42°S). The analysis performed in the paper are quite good, nevertheless I would suggest the authors to revise the temperature results.
I just have a couple of Major revisions, that can most likely be easily solved by the authors.
General Comments:
1) In the results section, the authors estimate the changes in temperature, as relative changes. To me, this makes no sense, because it is highly influenced by the baseline temperature. For example, if the baseline temperature is 10°C and one has a temperature increase of 1°C (between two different phases of ENSO), the percentage of change is a 10%, but if the baseline temperature was 0.5°C a 1°C increase would lead to a 200% change. In an even more extreme case if the baseline temperature of was -0.5°C a 1°C increase, would lead to a -200% change. To avoid, these types of problems I would recommend one of two options: Option 1) to use absolute temperature changes, or Option 2) to use relative changes, but with Kelvin degrees, which avoid all the issues beforementioned. Some of the results presented, I think might be influenced by using relative changes in temperature, and might mislead the reader of your article.
2) I would add an analysis of a trends, especially for temperature. If there is a temperature trend in the study zone and period, and given that most of the La Niña years have happened before 1980, that might bias your temperature analysis for “La Niña”, in case you detect temperatures increasing in time.
Minor Comments:
1) When describing CAMELS-CL in lines 178-181 you mention a list of attributes, but some of the attributes are not mentioned (for example, CAMELS-CL has information regarding water rights, Barría et al., 2021). If you do not want to mention all the attributes that is fine, but then sentence 181 should close with “among others” or equivalent. In case you want to list all the attributes mention the water rights and add “Barría et al., 2021” reference.
2) Given that you are mentioning the human intervention level in line 181 and then using it in Figure S1C, I would recommend you to revise and Cite Barría et al., (2021), as recommended in CAMELS-CL explorer page.
3) The specific discharges (Qsp) of Figure 3 are in “mm”? Please add the units in the axis, when using Qsp.
4) In Figure 3, when the gamma distribution process is described in the caption, you mention the “k” parameter. Although you mention it is the shape parameter in line 325, the caption of Figure 3 does not mention it, I would recommend to add it in the caption of Figure 3. Also, I assume you are referring to the Two Parameter Gamma distribution (and not the Three Parameter Gamma), it would be good to clarify this.
5) I would recommend to explicitly mention that the “k” parameter is the “shape parameter” in captions of Figures 5 and 7
Reference:
Barría, P., Sandoval, I. B., Guzman, C., Chadwick, C., Alvarez-Garreton, C., Díaz-Vasconcellos, R., Ocampo-Melgar, A., Fuster, R.: Water allocation under climate change: A diagnosis of the Chilean system. Elem Sci Anth, 9(1), 00131, https://doi.org/10.1525/elementa.2020.00131 , 2021.

Citation: https://doi.org/10.5194/egusphere-2022-1234-CC1
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1
RC1:
'Comment on egusphere-2022-1234', Anonymous Referee #1, 03 Feb 2023

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1234/egusphere-2022-1234-RC1-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2022-1234-RC1
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1
RC2:
'Comment on egusphere-2022-1234', Anonymous Referee #2, 30 Mar 2023
My sincere apology for the delay of the reviewing of this manuscript because of the un-expected crazy time recently. But I overall enjoyed the reading of
this manuscript in which the authors presented the ENSO impacts on the climatic and hydrological systems of the central Chile based on extensively distributed streamflow observations and rainfall products. Through the observation-based analysis, the authors re-confirmed the ENSO-Precipitation-streamflow relations in this region with detailed spatial and seasonal variations in interestingly recognized three hydrological regimes. Implications of water resources management is also well discussed based on the analysis. However, I do have several major comments for the authors to improve the manuscript as following:

Although the authors provided a lot of detailed results and discussions in different parts of the study domain under different ENSO phases, most texts are only presenting increasing/decreasing consequence of the precipitation/discharge responding to ENSO while lacking sufficient physical explanations for these informative analysis. This requires a major revision of the whole result/discussion sections to provide more in-depth analysis and discussion.

Highly related to the first comment, the conclusion does not add new information about the impacts of ENSO in this region compared to existing studies including those already mentioned in the manuscript. Although I endorse the reconfirmation of the knowledges using the ground observations, I would still like to see new interesting information which is not shown in the conclusion.

The definition of the three hydroclimate regimes needs to be better provided. The 178 discharge stations selected for this study needs to be carefully categorized into the three groups with the consideration of their upstream-downstream relations. For example, the downstream rain-dominant catchment could have upstream river flow inputs from the upstream high elevated snow-dominant catchments, making the analysis a bit complicated.

Skipping the period since 2010 (Lines 165-167) for the analysis might not be a good decision which surprises me actually. At least I would encourage the authors to report the analysis including this part. For example, the following reference shows the significant ENSO-flooding relations during a period of 1998-2013 over the study area. In addition, the reference presented a study using hydrological model simulated discharge without considering irrigation and reservoir operations, i.e., only natural hydrological process is considered, which could provide an useful reference for this study on less human-impacted catchments.

Yan Yan Huan Wu, Guojun Gu, Philip J. Ward Lifeng Luo Xiaomeng Li Zhijun Huang Jing Tao, 2020, Exploring the ENSO Impact on Basin‐Scale Floods Using Hydrological Simulations and TRMM Precipitation, Geophysical research Letters, https://doi.org/10.1029/2020GL089476

Figure 2. What is the range of the deltaQA and deltaK to be expected? The impact of the non-ENSO phase on the high- and low flow can be impacted by El Niño and La Niña phases, indicating a non-static non-ENSO phase is used as the reference. Would it be problematic, e.g., in understanding the range of deltaQA and deltaK?

Figure 2B. It is a bit hard for me to tell which are the non-ENSO events from those of La Nina events because of the colors used.
Citation: https://doi.org/10.5194/egusphere-2022-1234-RC2
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1

Status: closed

CC1:
'Comment on egusphere-2022-1234', Cristian Chadwick, 18 Jan 2023

Title: El Niño Southern Oscillation (ENSO)-induced hydrological anomalies in central Chile
Summary:
This paper presents a well written comprehensive work, related to the El Niño Southern Oscillation (ENSO) anomalies. In particular, there is a presentation of how the different phases of the ENSO affect the hydrological conditions in Central Chile (29-42°S). The analysis performed in the paper are quite good, nevertheless I would suggest the authors to revise the temperature results.
I just have a couple of Major revisions, that can most likely be easily solved by the authors.
General Comments:
1) In the results section, the authors estimate the changes in temperature, as relative changes. To me, this makes no sense, because it is highly influenced by the baseline temperature. For example, if the baseline temperature is 10°C and one has a temperature increase of 1°C (between two different phases of ENSO), the percentage of change is a 10%, but if the baseline temperature was 0.5°C a 1°C increase would lead to a 200% change. In an even more extreme case if the baseline temperature of was -0.5°C a 1°C increase, would lead to a -200% change. To avoid, these types of problems I would recommend one of two options: Option 1) to use absolute temperature changes, or Option 2) to use relative changes, but with Kelvin degrees, which avoid all the issues beforementioned. Some of the results presented, I think might be influenced by using relative changes in temperature, and might mislead the reader of your article.
2) I would add an analysis of a trends, especially for temperature. If there is a temperature trend in the study zone and period, and given that most of the La Niña years have happened before 1980, that might bias your temperature analysis for “La Niña”, in case you detect temperatures increasing in time.
Minor Comments:
1) When describing CAMELS-CL in lines 178-181 you mention a list of attributes, but some of the attributes are not mentioned (for example, CAMELS-CL has information regarding water rights, Barría et al., 2021). If you do not want to mention all the attributes that is fine, but then sentence 181 should close with “among others” or equivalent. In case you want to list all the attributes mention the water rights and add “Barría et al., 2021” reference.
2) Given that you are mentioning the human intervention level in line 181 and then using it in Figure S1C, I would recommend you to revise and Cite Barría et al., (2021), as recommended in CAMELS-CL explorer page.
3) The specific discharges (Qsp) of Figure 3 are in “mm”? Please add the units in the axis, when using Qsp.
4) In Figure 3, when the gamma distribution process is described in the caption, you mention the “k” parameter. Although you mention it is the shape parameter in line 325, the caption of Figure 3 does not mention it, I would recommend to add it in the caption of Figure 3. Also, I assume you are referring to the Two Parameter Gamma distribution (and not the Three Parameter Gamma), it would be good to clarify this.
5) I would recommend to explicitly mention that the “k” parameter is the “shape parameter” in captions of Figures 5 and 7
Reference:
Barría, P., Sandoval, I. B., Guzman, C., Chadwick, C., Alvarez-Garreton, C., Díaz-Vasconcellos, R., Ocampo-Melgar, A., Fuster, R.: Water allocation under climate change: A diagnosis of the Chilean system. Elem Sci Anth, 9(1), 00131, https://doi.org/10.1525/elementa.2020.00131 , 2021.

Citation: https://doi.org/10.5194/egusphere-2022-1234-CC1
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1
RC1:
'Comment on egusphere-2022-1234', Anonymous Referee #1, 03 Feb 2023

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-1234/egusphere-2022-1234-RC1-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2022-1234-RC1
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1
RC2:
'Comment on egusphere-2022-1234', Anonymous Referee #2, 30 Mar 2023
My sincere apology for the delay of the reviewing of this manuscript because of the un-expected crazy time recently. But I overall enjoyed the reading of
this manuscript in which the authors presented the ENSO impacts on the climatic and hydrological systems of the central Chile based on extensively distributed streamflow observations and rainfall products. Through the observation-based analysis, the authors re-confirmed the ENSO-Precipitation-streamflow relations in this region with detailed spatial and seasonal variations in interestingly recognized three hydrological regimes. Implications of water resources management is also well discussed based on the analysis. However, I do have several major comments for the authors to improve the manuscript as following:

Although the authors provided a lot of detailed results and discussions in different parts of the study domain under different ENSO phases, most texts are only presenting increasing/decreasing consequence of the precipitation/discharge responding to ENSO while lacking sufficient physical explanations for these informative analysis. This requires a major revision of the whole result/discussion sections to provide more in-depth analysis and discussion.

Highly related to the first comment, the conclusion does not add new information about the impacts of ENSO in this region compared to existing studies including those already mentioned in the manuscript. Although I endorse the reconfirmation of the knowledges using the ground observations, I would still like to see new interesting information which is not shown in the conclusion.

The definition of the three hydroclimate regimes needs to be better provided. The 178 discharge stations selected for this study needs to be carefully categorized into the three groups with the consideration of their upstream-downstream relations. For example, the downstream rain-dominant catchment could have upstream river flow inputs from the upstream high elevated snow-dominant catchments, making the analysis a bit complicated.

Skipping the period since 2010 (Lines 165-167) for the analysis might not be a good decision which surprises me actually. At least I would encourage the authors to report the analysis including this part. For example, the following reference shows the significant ENSO-flooding relations during a period of 1998-2013 over the study area. In addition, the reference presented a study using hydrological model simulated discharge without considering irrigation and reservoir operations, i.e., only natural hydrological process is considered, which could provide an useful reference for this study on less human-impacted catchments.

Yan Yan Huan Wu, Guojun Gu, Philip J. Ward Lifeng Luo Xiaomeng Li Zhijun Huang Jing Tao, 2020, Exploring the ENSO Impact on Basin‐Scale Floods Using Hydrological Simulations and TRMM Precipitation, Geophysical research Letters, https://doi.org/10.1029/2020GL089476

Figure 2. What is the range of the deltaQA and deltaK to be expected? The impact of the non-ENSO phase on the high- and low flow can be impacted by El Niño and La Niña phases, indicating a non-static non-ENSO phase is used as the reference. Would it be problematic, e.g., in understanding the range of deltaQA and deltaK?

Figure 2B. It is a bit hard for me to tell which are the non-ENSO events from those of La Nina events because of the colors used.
Citation: https://doi.org/10.5194/egusphere-2022-1234-RC2
- AC1: 'Combined reply on RC1, RC2 and CC1.', Renee van Dongen, 05 May 2023
  
  Due to text formatting issues in the commenting system, we've uploaded the authors' response as an attachment (PDF) to this reply.
  
  Citation: https://doi.org/10.5194/egusphere-2022-1234-AC1

Renee van Dongen, Dirk Scherler, Dadiyorto Wendi, Eric Deal, Luca Mao, Norbert Marwan, and Claudio I. Meier

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https://doi.org/10.5194/egusphere-2022-1234-supplement

Renee van Dongen, Dirk Scherler, Dadiyorto Wendi, Eric Deal, Luca Mao, Norbert Marwan, and Claudio I. Meier

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Short summary

El Niño Southern Oscillation (ENSO) is a climatic phenomenon that causes abnormal climatic conditions in Chile. We investigated how ENSO affects catchment hydrology and found strong seasonal and spatial differences in the hydrological response to ENSO which was caused by different hydrological processes in catchments that are dominated by snowmelt-generated runoff or rainfall-generated runoff. These results are relevant for water resources management and ENSO mitigation in Chile.


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