the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 May 2024
Spatially explicit assessment of water scarcity and potential mitigating solutions in a large water-limited basin: the Yellow River basin in China
Abstract. Comprehensive assessment of the long-term evolution of water scarcity and its driving factors is essential for designing effective water resource management strategies. However, the role of water withdrawal and water availability components in determining water scarcity and potential mitigating measures in large water-scarce basins are poorly understood. Here, an integrated analytical framework was applied to the Yellow River basin (YRB), where the water crisis has been a core issue for sustainable development. Analysis of the water scarcity index (WSI) and other critical indicators, including frequency, duration, and exposed population, suggest that the YRB experienced unfavorable changes in water crisis during 1965‒2013. Irrigation dominated the increase in WSI in the northwest part of the basin before 2000, whereas climate change was primarily responsible for changes in the WSI in most sub-basins during the recent decade. Meanwhile, local water management and climate change adaptation were shown to be important in determining total water availability at the sub-basin scale. Water demand in the 2030s is predicted to be 37.4 km3 based on the trajectory of historical water use, worsening 28.7 % and easing 12.5 % of the total population, respectively. To meet all sectoral water needs, a 10 km3 water deficit is projected. The potential improvements in irrigation efficiency could solve 26 % of this deficit, thereby easing the pressure on external water transfer projects. In conclusion, the integration of water supply and demand-oriented strategies is essential to effectively alleviate the water crisis in the YRB. Our results have vital implications for water resource management in basins facing similar water crises to that in the YRB.
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RC1: 'Comment on hess-2024-88', Anonymous Referee #1, 14 May 2024
This study addresses the critical issue of water scarcity in the Yellow River Basin, presenting a novel and comprehensive assessment framework for analyzing water shortage. By utilizing a combination of models and statistical data, it explores the spatiotemporal changes in this severely water-deficient river basin over a span of nearly sixty years and provides insightful predictions for the future. The research question, which is a unique and crucial aspect in the field, is clearly defined, the thought process is clear, and the logical chain is complete, resulting in scientifically valuable information and conclusions. The figures are also well-designed. However, before formal publication, I have some suggestions for consideration by the authors:
- The abstract and the primary texts are too extended; it's recommended that they be simplified and the main contributions highlighted.
- In lines L103-L105, explicitly addressing the deficiencies in previous studies would be beneficial. For instance, what specific challenges do global water stress assessments face? This requires further clarification. Additionally, the decision not to consider upstream inflow and consumption, while not a significant issue in my view, should be explained or referenced to strengthen the paper's argument.
- In line L122 regarding environmental flow requirements, there has been extensive discussion of this flow rate of Yellow River from different perspectives, leading to varied estimates; you need to elaborate on how you evaluated these considerations here.
- In Figure 2 and the introduction of the study area - clarify how you distinguish between upstream and downstream regions. Or rather, readers expect an understanding of how upstream usage creates pressure on downstream resources within your study area description.
- On the Yellow River, policy-making & unified dispatching already dominate human water use. In your proposed analysis framework emphasizing coordination with upstream, does such coordination significantly impact the basin system?
- We understand that Zhou's data only went up until 2013. Still, the authors need to find ways to explain that the lack of data from the recent decade will not lead to outdated trends affecting analysis or causing bias in conclusion.
- During the discussion, it is necessary to include a comparative analysis with previous calculations using other water shortage indicators. This will highlight how the contributions of this assessment can compensate for the shortcomings of previous ones.
Citation: https://doi.org/10.5194/hess-2024-88-RC1 -
AC1: 'Reply on RC1', Baoqing Zhang, 23 Jul 2024
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-88/hess-2024-88-AC1-supplement.pdf
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RC2: 'Comment on hess-2024-88', Anonymous Referee #2, 28 May 2024
The manuscript provides an in-depth analysis of water scarcity in the Yellow River Basin (YRB) using an integrated analytical framework. The study spans from 1965 to 2013, focusing on critical indicators like the Water Scarcity Index (WSI), frequency, duration, and exposed population. It also projects future water demand and evaluates potential solutions, particularly improving irrigation efficiency.
General Comments
The study addresses a crucial topic in hydrology and water resources management, particularly for a region as significant as the YRB. Integrating historical data, model simulations, and future projections provides a comprehensive overview. However, several areas could benefit from further clarification and refinement:
- In the introduction, the authors list the limitations of previous studies regarding water use and water withdrawal estimation, highlighting their implications for water stress assessments. While the study acknowledges these limitations and aims to address them, many of the same uncertainties are reiterated in the uncertainty section (section 4.3). This raises the question: if these limitations remain largely unresolved, why emphasize them in the introduction?
- The authors' statements in the introduction about the limitations of previous studies using coarse spatial resolution global water scarcity assessments (e.g., 0.5° × 0.5° level) and neglecting upstream water availability are partly valid. However, there are existing studies that have addressed water scarcity in the Yellow River Basin (YRB) at a higher resolution, considering sub-basin scales and upstream water availability (e.g., Albers et al., 2021; Omer et al., 2020; Xie et al., 2020). Given this and the previous comment, the authors should revise the motivation section of the introduction accordingly.
- The manuscript mentions the use of the SWAT model for simulating natural water availability. While the validation against hydrological station data is noted in section 2.4, detailed validation results and statistics (e.g., NSE, R2, P-factor, and R-factor) were not provided in the manuscript. These metrics are important to assess and understand the model's performance comprehensively.
- In section 2.4 the authors re-run the SWAT model with fixed land use in 1990 but varied climatic conditions to assess the impact of vegetation restoration. By fixing land use to the conditions of 1990, the model controls for the influence of land cover and land use changes. Any changes observed in water availability or WSI in this experiment can thus be attributed solely to climatic variations NOT vegetation restoration, isn’t it?
- The introduction section in the study highlights a 120% increase in total water consumption, including both surface and groundwater, in the YRB from the 1960s to 2009. However, upon reviewing the methods and results sections, it is apparent that groundwater pumping and usage were not directly factored into the water availability calculations used in the water scarcity equation. Omitting this factor may lead to an underestimation of water availability and, thus, an overestimation of water scarcity levels.
- The study's prioritization of water use sectors during future water stress periods aims to mitigate socio-economic impacts by focusing on essential needs. However, this approach is unreliable due to two-sided uncertainties. First, using past period (P4: 2000-2013) water availability to calculate future water deficits ignores the high variability in water availability and the impacts of global climate change, making stationarity an invalid assumption. Second, projecting future water demands based solely on historical trends fails to account for potential changes in socio-economic dynamics and policies, which could significantly alter future demands. While the authors acknowledge the limitations of using P4 water availability and historical water demand trends, I think the resulting water allocation prioritization remains unreliable for policymakers. Addressing uncertainties on at least one side would improve the reliability of the prioritization framework.
- Additionally, the study's exclusion of the most recent decade (2013-2023) raises concerns. This period has seen significant changes in both water availability and demand, advances in data collection, and new policies and management practices. Incorporating recent data would provide a more accurate and up-to-date assessment of water scarcity in the Yellow River Basin (YRB), reflecting current conditions and offering a better foundation for future projections and management strategies. Including this recent decade would enhance the study's relevance and accuracy, making it more useful for policymakers.
- The manuscript effectively highlights potential improvements in irrigation efficiency as a key strategy for mitigating future water stress in the Yellow River Basin (YRB). However, it would benefit from a more comprehensive analysis or discussion on the feasibility of achieving these efficiency improvements.
Minor Comments
- Figures and Tables:
- Figure 1 lacks a legend to explain the various elements used in the diagram. I think clarifying the meaning of the solid and dashed arrows, different rectangular colors, shapes, and outlines would help to understand the content of the figure.
- Figures 3, 4, and 7 are central to the manuscript's findings but could be clarified. Ensure that all figures have clear legends, labels, and units. Color gradients should be distinct enough for readers to differentiate between categories. Moreover, ensure all figures and tables are referenced in the text and clearly explained. For example, Figure 3 is mentioned, but its significance and interpretation could be better integrated into the discussion.
- The use of the terms and definitions: Throughout the manuscript, ensure consistent use of terms and clear definitions. For example, ensure terms like “water scarcity,” “water stress,” and “water availability” are defined clearly and used consistently to avoid confusion.
Citation: https://doi.org/10.5194/hess-2024-88-RC2 -
AC2: 'Reply on RC2', Baoqing Zhang, 23 Jul 2024
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-88/hess-2024-88-AC2-supplement.pdf
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