the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Aug 2023
Unveiling Hydrological Dynamics in Data-Scarce Regions: A Comprehensive Integrated Approach
Abstract. The hydrological system of Rift Valley Lakes in Ethiopia has recently experienced changes since the past two decades. Potential causes for these changes include anthropogenic, hydro-climatic and geological factors. The main objective of this study was to utilize an integrated methodology to gain a comprehensive understanding of the hydrological systems and potential driving factors within a complex and data-scarce region. To this end, we integrated a hydrologic model, change point analysis, indicators of hydrological alteration (IHA), and bathymetry survey to investigate hydrological dynamics and potential causes. A hydrologic model (SWAT+) was parameterized for the gauged watersheds and extended to the ungauged watersheds using multisite regionalization techniques. The SWAT+ model performed very good to satisfactory for daily streamflow in all watersheds with respect to the objective functions, Kling–Gupta efficiency (KGE), the Nash–Sutcliffe efficiency (NSE), Percent bias (PBIAS). The findings reveal notable changes of lake inflows and lake levels over the past two decades. Chamo Lake experienced an increase in area by 11.86 km², in depth by 4.4 m, and in volume by 7.8 x 108 m³. In contrast, Lake Abijata witnessed an extraordinary 68% decrease in area and a depth decrease of 1.6 m. During the impact period, the mean annual rainfall experienced a decrease of 6.5% and 2.7% over the Abijata Lake and the Chamo Lake, respectively. Actual evapotranspiration decreased by 2.9% in Abijata Lake but increased by up to 0.5% in Chamo Lake. Surface inflow to Abijata Lake decreased by 12.5%, while Lake Chamo experienced an 80.5% increase in surface inflow. Sediment depth in Chamo Lake also increased by 0.6 m. The results highlight that the changing hydrological regime in Chamo Lake is driven by increased surface runoff and sediment intrusion associated with anthropogenic influences. The hydrological regime of Abijata Lake is affected by water abstraction from feeding rivers and lakes for industrial and irrigation purposes. This integrated methodology provides a holistic understanding of complex data scarce hydrological systems and potential driving factors in the Rift Valley Lakes in Ethiopia, which could have global applicability.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
(2903 KB)
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2903 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1895', Anonymous Referee #1, 07 Dec 2023
The manuscript titled “Unveiling Hydrological Dynamics in Data-Scarce Regions: A Comprehensive Integrated Approach” authored by Ayalew et al., is a compelling work that is both well-structured and comprehensive. It provides a detailed analysis of hydrological changes in the Rift Valley lakes region, Ethiopia, presenting valuable and transferable methodological approaches in the context of regionalization, specifically in donor and pseudo watershed categorization. Additionally, the numerical analysis resulted in a valuable database for the study region.
However, I have two points that require clarification:
In reference to the SWAT+ modelling approach, the authors used the variable storage routing method for river routing. Could the authors provide justification for the choice of the variable storage routing method?
While the study effectively highlights substantial hydrologic changes in the region, the authors attribute these changes to climate change and human impacts. It would be beneficial for the authors to elaborate on which driver—climate change or human impacts—had a more pronounced effect on altering the hydrologic regime in the study area.
These clarifications would enhance the understanding of the methodology and findings presented in the manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-1895-RC1 -
AC1: 'Reply on RC1', Ayenew Desalegn Ayalew, 04 Jan 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1895/egusphere-2023-1895-AC1-supplement.pdf
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AC1: 'Reply on RC1', Ayenew Desalegn Ayalew, 04 Jan 2024
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RC2: 'Comment on egusphere-2023-1895', Anonymous Referee #2, 16 Dec 2023
The authors aim to characterize the hydrological changes in two lakes in Ethiopia through a comprehensive evaluation employing a hydrological model (SWAT+) and bathymetry analysis. The study categorizes the time period into pre-impacted, impacted, and post-impacted phases to elucidate the observed changes. Results indicate a depletion of lake storage during the impacted period for both lakes, with varying recovery patterns—one lake exhibits increased storage compared to the pre-impacted period, while the other experiences a decline. The identified changes are attributed to factors such as climate change, land use alterations, and human water extraction.
The manuscript is well-crafted, particularly in the conclusion section; however, some sections, notably the results, require clarification. Below are suggested improvements:
Title: The title lacks a description of the study area. Given the regional focus, incorporating the study area in the title is recommended.
Abstract:
P1 L20-21, 26: Providing %age values would be better.
P1 L23-24: very small changes in ET compared to inflow changes.
The introduction gives a good description of the study area, but it can be condensed. The contribution/novelty of the manuscript needs to be highlighted. Although the objectives are mentioned at the end of the introduction section, the research questions should be clearly articulated.
Methods: The method section is well written. There are a few queries/suggestions though.
Study area: Is the 1st paragraph really needed?
P6 L1: How is the slope % calculated?
P6 L21: Why was SRTM DEM used despite the availability of better DEM data such as FABDEM and MERIT DEM?
P6 L21: Electricity?
P7, L22-24: I like the idea of dividing the durations into high-pulse and low-pulse periods. However, it was quite difficult for me to understand the pre-impacted, impacted, and post-impacted period. Kindly define these properly.
P7 L13-22 can be incorporated into Table 2.
P8, L5/ P7 L13-22: Group3 data cannot be always associated with flood and drought. Low flow and high flow doesn’t necessarily mean its flooding or it’s a drought period. Also kindly explain the uncertainty associated with the dates (likely in the discussion section). There can be several dates within ±5% of the minimum and maximum values. Also, please explain how pulse count and pulse duration were calculated.
Results
Figures 4 and 5: kindly mention at least one matrix in the figure even though it is provided in Table 4.
P20: The analysis is good. Kindly mention which data is modeled and which is observed. Also, please validate the modeled data wherever possible. One major concern I have here is that the enclosure term is quite large for both lakes.
P21 L3 L9: Figure 8?
P21 L4: on what basis were the impact periods determined?
P21 L9: can you please briefly describe the environmental flow analysis in the methods section?
P21 L12: please don’t use the word “flood” alternatively for the high flow and extreme high flow. These may be extreme flows, but not necessarily flood events.
P22 L7-8: Please reframe the sentence.
P23 L12: Kindly provide a reference for association with deforestation.
P24: It is very important to discuss the causes and impact of these changes, which I find missing. This would significantly increase the quality of the manuscript.
P27 L1-2: which changes led to these differences between the two lakes?
P27 L5-8: why does the lake level increase for one and decrease for the other?
P30 L4-5: Here and elsewhere, please mention %age change.
P30: Isn’t the figure a part of figure 12? Please mention the caption.
Discussions
P32 L2-20: Can you please make it concise? Particularly L2-13 doesn’t hold much scientific value.
P33 L3: a decrease of
Additionally, address uncertainties in the study within the discussion section.
Citation: https://doi.org/10.5194/egusphere-2023-1895-RC2 -
AC2: 'Reply on RC2', Ayenew Desalegn Ayalew, 04 Jan 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1895/egusphere-2023-1895-AC2-supplement.pdf
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AC2: 'Reply on RC2', Ayenew Desalegn Ayalew, 04 Jan 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-1895', Anonymous Referee #1, 07 Dec 2023
The manuscript titled “Unveiling Hydrological Dynamics in Data-Scarce Regions: A Comprehensive Integrated Approach” authored by Ayalew et al., is a compelling work that is both well-structured and comprehensive. It provides a detailed analysis of hydrological changes in the Rift Valley lakes region, Ethiopia, presenting valuable and transferable methodological approaches in the context of regionalization, specifically in donor and pseudo watershed categorization. Additionally, the numerical analysis resulted in a valuable database for the study region.
However, I have two points that require clarification:
In reference to the SWAT+ modelling approach, the authors used the variable storage routing method for river routing. Could the authors provide justification for the choice of the variable storage routing method?
While the study effectively highlights substantial hydrologic changes in the region, the authors attribute these changes to climate change and human impacts. It would be beneficial for the authors to elaborate on which driver—climate change or human impacts—had a more pronounced effect on altering the hydrologic regime in the study area.
These clarifications would enhance the understanding of the methodology and findings presented in the manuscript.
Citation: https://doi.org/10.5194/egusphere-2023-1895-RC1 -
AC1: 'Reply on RC1', Ayenew Desalegn Ayalew, 04 Jan 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1895/egusphere-2023-1895-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Ayenew Desalegn Ayalew, 04 Jan 2024
-
RC2: 'Comment on egusphere-2023-1895', Anonymous Referee #2, 16 Dec 2023
The authors aim to characterize the hydrological changes in two lakes in Ethiopia through a comprehensive evaluation employing a hydrological model (SWAT+) and bathymetry analysis. The study categorizes the time period into pre-impacted, impacted, and post-impacted phases to elucidate the observed changes. Results indicate a depletion of lake storage during the impacted period for both lakes, with varying recovery patterns—one lake exhibits increased storage compared to the pre-impacted period, while the other experiences a decline. The identified changes are attributed to factors such as climate change, land use alterations, and human water extraction.
The manuscript is well-crafted, particularly in the conclusion section; however, some sections, notably the results, require clarification. Below are suggested improvements:
Title: The title lacks a description of the study area. Given the regional focus, incorporating the study area in the title is recommended.
Abstract:
P1 L20-21, 26: Providing %age values would be better.
P1 L23-24: very small changes in ET compared to inflow changes.
The introduction gives a good description of the study area, but it can be condensed. The contribution/novelty of the manuscript needs to be highlighted. Although the objectives are mentioned at the end of the introduction section, the research questions should be clearly articulated.
Methods: The method section is well written. There are a few queries/suggestions though.
Study area: Is the 1st paragraph really needed?
P6 L1: How is the slope % calculated?
P6 L21: Why was SRTM DEM used despite the availability of better DEM data such as FABDEM and MERIT DEM?
P6 L21: Electricity?
P7, L22-24: I like the idea of dividing the durations into high-pulse and low-pulse periods. However, it was quite difficult for me to understand the pre-impacted, impacted, and post-impacted period. Kindly define these properly.
P7 L13-22 can be incorporated into Table 2.
P8, L5/ P7 L13-22: Group3 data cannot be always associated with flood and drought. Low flow and high flow doesn’t necessarily mean its flooding or it’s a drought period. Also kindly explain the uncertainty associated with the dates (likely in the discussion section). There can be several dates within ±5% of the minimum and maximum values. Also, please explain how pulse count and pulse duration were calculated.
Results
Figures 4 and 5: kindly mention at least one matrix in the figure even though it is provided in Table 4.
P20: The analysis is good. Kindly mention which data is modeled and which is observed. Also, please validate the modeled data wherever possible. One major concern I have here is that the enclosure term is quite large for both lakes.
P21 L3 L9: Figure 8?
P21 L4: on what basis were the impact periods determined?
P21 L9: can you please briefly describe the environmental flow analysis in the methods section?
P21 L12: please don’t use the word “flood” alternatively for the high flow and extreme high flow. These may be extreme flows, but not necessarily flood events.
P22 L7-8: Please reframe the sentence.
P23 L12: Kindly provide a reference for association with deforestation.
P24: It is very important to discuss the causes and impact of these changes, which I find missing. This would significantly increase the quality of the manuscript.
P27 L1-2: which changes led to these differences between the two lakes?
P27 L5-8: why does the lake level increase for one and decrease for the other?
P30 L4-5: Here and elsewhere, please mention %age change.
P30: Isn’t the figure a part of figure 12? Please mention the caption.
Discussions
P32 L2-20: Can you please make it concise? Particularly L2-13 doesn’t hold much scientific value.
P33 L3: a decrease of
Additionally, address uncertainties in the study within the discussion section.
Citation: https://doi.org/10.5194/egusphere-2023-1895-RC2 -
AC2: 'Reply on RC2', Ayenew Desalegn Ayalew, 04 Jan 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-1895/egusphere-2023-1895-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Ayenew Desalegn Ayalew, 04 Jan 2024
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Ayenew D. Ayalew
Paul D. Wagner
Dejene Sahlu
Nicola Fohrer
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(2903 KB) - Metadata XML