The North China Plain relies heavily on deep confined groundwater to alleviate irrigation water shortages during drought years. However, conventional static groundwater control levels are often unable to reflect intra-seasonal changes in groundwater storage and stage-specific water demand, and therefore cannot directly support pumping control during drought periods. To address this issue, this study develops a stage-based groundwater-threshold framework for drought-year irrigation management in deep confined aquifers. The framework adopts a dual temporal structure consisting of a drought management period and rolling guarantee periods. It combines a sliding baseline groundwater level with staged drought-limit groundwater levels (DLGWLs), and determines stage-specific regulation thresholds based on groundwater abstraction, relative recharge, aquifer storage conditions, and planned water demand. The framework was applied to two representative study areas in the North China Plain. The results show that, in the recovering-type groundwater system, the overall supply adjustment factor α was 1, and the DLGWLs mainly served as tools for verifying the planned abstraction scheme and supporting early-warning verification. In the declining or unstable-recovery groundwater system, the overall supply adjustment factor α and pumping adjustment factor β were 0.9756 and 0.9695, respectively, indicating that the framework can identify regulation trigger points and determine the required intensity of pumping reduction. Monte Carlo analysis showed that, under the no-regulation scenario, the probabilities of groundwater levels falling below the sliding baseline groundwater level at the end of the drought management period were 8.30% in Jizhou District and 60.22% in Xinji District, indicating a higher baseline-breach risk in the declining or unstable-recovery groundwater system. The proposed framework provides an operational basis for safe deep confined groundwater supply, stage-specific threshold management, and pumping control during drought years.

Against the backdrop of global climate change, drought-flood abrupt alternation (DFAA) events have become increasingly frequent, yet the research on their driving mechanisms remains in the exploratory stage. To address the limitation of existing studies that focus primarily on the linear effects of climate change and atmospheric circulation, this study incorporated multiple factors, including surface energy fluxes, to conduct a multidimensional analysis. Using a revised DFAA index (R-SDFAI), we systematically analyzed the linear time-lag effects and nonlinear interactions of these factors on global DFAA across different lag times, employing Pearson correlation coefficients, multiple linear regression, and interpretable machine learning models. The study found that DFAA events were most frequent and intense in continental climate zones, whereas overall risk was relatively low in tropical climate zones. After accounting for time-lag effects, the explanatory power of multiple factors on DFAA increased from 33.03% to 70.05%, revealing clear spatial heterogeneity. For instance, in tropical climate zones, DFAA was bidirectionally influenced by vapor pressure deficit, whereas in arid climate zones, net radiation exhibited bidirectional associations with DFAA. After removing intra-annual seasonal signals, the dominant relationship converged on the moisture component. The study further revealed the key nonlinear threshold regulation of multiple factors, including the negative impacts of high net radiation and low rainfall in tropical climate zones, and the synergistic reversal driven by low heat flux and solar-induced chlorophyll fluorescence in arid climate zones. These findings transcended conventional linear frameworks for DFAA analysis, laying a scientific foundation for accurate prediction and disaster prevention.

Drought-flood abrupt alternation (DFAA) events are an important manifestation of instability in the global climate system and pose substantial risks to society and ecosystems. However, the risks that DFAA events impose on affected systems have not yet been systematically quantified at the global scale. Based on the three key components of hazard, exposure, and vulnerability, this study applies a multiplicative model to assess global DFAA risk, develops a "double-mean, double-threshold, and double-driver" analytical framework, quantifies the effective risks of DFAA events to social and ecological systems, and identifies their major influencing factors. The results showed that, although the global mean DFAA hazard increased slightly, regional differences are pronounced. The social system exhibited a pattern of increasing exposure and decreasing vulnerability, whereas the ecosystem showed simultaneous increases in both exposure and vulnerability. Although the spatial extent of flood-to-drought risk was smaller than that of drought-to-flood risk, it was more destructive in some regions. The overall centroid of social system risk shifted toward the southeast and southwest, whereas that of ecosystem risk shifted toward the northeast. The mechanisms driving risk also showed pronounced asymmetry, with socioecological system factors dominating during the drought-to-flood stage and climatic factors playing a leading role during the flood-to-drought stage. Overall, this study reveals the differences in DFAA risk and the asymmetric driving characteristics affecting social and ecological systems at the global scale, providing a scientific basis for risk warning, adaptive management, and sustainable development decision-making related to DFAA events.

To address the increasing frequency and severity of droughts worldwide, water resource management strategies should prioritize enhancing resilience and adaptability to drought and water shortages. This paper focuses on water resource management issues in drought-prone areas with diversified water supply structures. It proposes and validated a framework to enhance the drought resilience of combined surface water and groundwater supply systems. Based on the concept of risk hedging, the framework constructs a combined water supply model of surface water and groundwater using General Water Allocation and Simulation Model (GWAS). It refines the calculation of drought limit water levels for each water source and their operational strategies. This study applied the framework to a typical drought-prone area in the North China Plain. It evaluated the effect of drought-limited water levels and their operation strategies on drought resilience of the water supply system based on the analysis of the overall drought resilience of various local water sources. The results indicated significant improvements in the reliability, resiliency, and vulnerability of the combined surface water and groundwater supply area during dry years. This framework optimizes the spatiotemporal distribution of water resources, transforming continuous extreme damage into milder wide-shallow damage, accelerating the speed of system restoration of water supply, and effectively mitigating extreme water shortages at the end of dry years. The research provides new insights and methods for water resource management in drought-prone areas, highlighting its importance for enhancing drought resilience and achieving stable, sustainable water resource utilization.

With the increasing frequency of global drought events, implementing effective monitoring and early warning systems is essential. The drought-limited water level (DLWL) is a new indicator for drought management in China. This study proposes a refined optimization method for determining the DLWL and drought-resistant operational strategies for each reservoir in multi-reservoir systems based on a general water allocation and simulation model. This study takes representative reservoirs in the North China Plain as a case study. Results show that DLWL effectively mitigates regional water shortages during droughts, reducing overall shortages by 12

Drought is increasingly recognized as a severe global risk, yet the ability to predict drought remains limited, particularly in capturing early warning signals. This study breaks through the limitations of existing drought prediction by combining causal inference and multiple machine learning models from an energy perspective, as well as designing adaptive preference algorithms to establish a framework for the dynamic identification of drought propensity, which is applied to the United States, Argentina, Congo, and the Yangtze River Basin. The findings reveal a causal lag effect (4-12 months) between surface energy flux fluctuations and drought. The ability of energy fluxes to predict drought index and identify drought propensity is different in different regions and different models, which may be affected by climatic diversity. Models for the United States and Argentina achieved R2 values of 0.85-0.91, with drought propensity identification accuracy reaching up to 80 %. In contrast, the Yangtze River Basin showed lower performance, with an accuracy of 56 %. Furthermore, the energy dominant factors in different regions vary significantly. Their energy thresholds (such as the net radiation of the United States at 132.87 W/m2 and the latent heat flux of the Yangtze River at 108.50 W/m2) and their action directions reveal the essential differences in the land-air energy distribution mechanisms in different regions. These results highlight the predictive potential of surface energy fluxes in drought events and underscore their importance for global drought prediction models. This research offers valuable insights into improving global drought prediction systems and enhancing climate risk management strategies.

As an important indicator and basis for early warning of drought, water shortages, and anti-drought planning in water conservancy projects, the drought-limited water level (DLWL) plays an important role in scientific guidance of the drought control of lakes.This study focused on the characteristics of controlled water supply lakes, while also fully considering the ecological health and stability of the lakes and combining with the reverse recursive calculation of lake utilization regulation.Thus, we developed a method for calculating the DLWL of controlled water supply lakes.The rationality of this method was verified through a case analysis of Erhai Lake, Yunnan Province, China.The results showed that the severe water shortage in drought years can be alleviated effectively by setting the DLWL and considering the minimum ecological demand of the lake.The maximum reduction in water shortage for the water supply of the region surrounding Erhai is as high as 10.23 million m3, and the maximum reduction in agricultural irrigation water from Erhai entering Binchuan County is as high as 10.16 million m3.Additionally, the water shortage rate and period in each industrial sector can be reduced significantly in areas around the lake.The time period during which the lake is below the ecological water level can also be reduced significantly.After setting the DLWL, the number of severe water shortage months for lake water supply and the Erhai water entering Binchuan County irrigation was reduced by 11 and 10 months, respectively, and the duration time below the ecological water level was reduced by 15 days.This study provides a general algorithm that can be used by flood and drought disaster prevention departments to establish a DLWL and guide the drought-relief operation of a lake, which can provide the scientific basis and technical support required for drought prevention.

Water, soil, and heat are strategic supporting elements for human survival and social development. The degree of matching between human-land-water-heat elements directly influences the sustainable development of a region. However, the current evaluation of the matching of human-land-water-heat elements overlooks the influence of elevation factors on the matching results, especially evident in mountainous areas. Taking the Yunnan Plateau with distinctive mountainous features as the research subject, divided into 11 elevation ranges, the Lorenz Gini coefficient, asymmetry coefficient, matching distance, and imbalance index are used to assess the spatial matching and balance of human-land-water-heat elements. A projection tracing model is employed to analyze its water resource carrying capacity. Analyses revealed that the Gini coefficient of monthly precipitation from the 1950s to 2022 on the Yunnan Plateau increases with increasing latitude, whereas the correlation with elevation is notably lower. The asymmetry coefficient increases gradually from west to east with change in longitude. The mismatch of the human–land–water–heat system in regions at different elevations is in the order 1800–2000 m > 2000–2200 m > 1400–1600 m > 800 m > other areas. The matching of the human–land–water–heat system in different wet–dry years and seasons also fluctuates with elevation, resulting in serious seasonal drought and water shortage problems in mountainous areas with elevations of 1200–1600, 1800–2000 m, and >2600 m. The spatial equilibrium of temperature and precipitation in regions of different elevations is best, followed by that of cultivated land, while that of the population is the worst. The Gini coefficients for different water cycle processes of precipitation, surface runoff, and regulating storage capacity for water supply continue to increase. Specifically, the Gini coefficient of industrial water supply is the highest, reaching 0.576, and that of agricultural irrigation is the lowest (0.424). Through artificial regulation of lake and reservoir water, seasonal changes in the demand for agricultural irrigation water are offset to achieve a demand–supply balance and matching of land and water resources. The water resource capacity of different elevation ranges is evenly underloaded. However, the potential of the water resource capacity varies obviously with elevation in the order 2000–2200 m < 1800–2000 m < 1600–8000 m < 1400–1600 m < other areas. It appears that the greater the human–land–water–heat system mismatch, the smaller the regional potential of the water resource capacity.

Drought evolution is a complex dynamic process, showing continuous characteristics in space-time. Currently, the researches on drought dynamics from multiple dimensions are limited and should be improved further. Therefore, a three-dimensional identification method was adopted to investigate the spatiotemporal patterns of classified drought events (namely two-month drought events, within-year drought events, and cross-year drought events) in northwest China during1961-2018. Furthermore, more spatial variables of drought event, such as start and end location, drought orientation and rotation, were extracted to describe the dynamic migration trajectories of drought events. Significantly, drought rotation helped to reveal the forcing mechanisms (such as the influence of climate and land surface) behind their spatial development. The results showed that a total of 169 drought events were identified over 1961-2018, and drought variables (duration, area, severity, and migration distance) represented fluctuating decreasing trend with the rate of - 0.135/10a, - 0.006/10a, - 0.16/10a, and - 5.67/ 10a. The dynamic migration process of individual drought event was objectively and effectively depicted from a three-dimensional perspective, which was consistent with the historical drought records in study area. Regarding the classified events, drought magnitude was more severe in 1961-1980 than that in 1981-2018, and three primary migration patterns (east-to-east, west-to-west, and south-to-south) were identified in northwest China. Within-year drought events mostly started in the first three quarters and finished in the second half year, whilst the situation was reversed for the cross-year drought events. Spatially, Alxa League of Inner Mongolia and northwest Qinghai Province were two main drought centers. Additionally, drought events characterized by clockwise rotation migration were mostly distributed in the plateau and southeast climate zones, and that was anticlockwise rotation in the westerly climate zone. Noticeably, the east-to-east pathways were mainly located in the east part of the study area, while the west-to-west and south-to-south trajectories were dominated in the west part.

Climate change and anthropogenic activity are the primary drivers of water cycle changes. Hydrological droughts are caused by a shortage of surface and/or groundwater resources caused by climate change and/or anthropogenic activity. Existing hydrological models have primarily focused on simulating natural water cycle processes, while limited research has investigated the influence of anthropogenic activities on water cycle processes. This study proposes a novel framework that integrates a distributed hydrological model and an attribution analysis method to assess the impacts of climate change and anthropogenic activities on hydrological drought The distributed dualistic water cycle model was applied to the Fuhe River Basin (FRB), and it generated a Nash-Sutcliffe efficiency coefficient > 0.85 with a relative error of <5 %. Excluding the year with extreme drought conditions, our analysis revealed that climate change negatively impacted the average drought duration (-105.5 %) and intensity (-23.6 %) because of increasing precipitation. However, anthropogenic activities continued to contribute positively to the drought, accounting for 5.5 % and 123.6 % of the average drought duration and intensity, respectively, because of increased water consumption. When accounting for extreme drought years, our results suggested that climate change has contributed negatively to the average duration of drought (-113.2 %) but positively to its intensity (7.8 %). Further, we found that anthropogenic activities contributed positively to both the average drought duration and intensity (13.2 % and 92.2 %, respectively). While climate change can potentially mitigate hydrological drought in the FRB by boosting precipitation levels, its overall effect may exacerbate drought through the amplification of extreme climate events resulting from global climate change. Therefore, greater attention should be paid to the effects of extreme drought.

全球变化背景下特大干旱综合应对研究是国家重大实践需求和科技前沿课题.大范围、长历时、高强度特大干旱具有"点面监测难协同、发展态势难预报、旱情程度难诊断、供需调控难兼顾"等防控难点.本研究提出特大干旱防控应对的三大关键科学问题,在"理论研究-技术开发-装备研制"的总体思路下,未来应以多技术融合为手段,在现有干旱防御技术体系基础上,进一步系统揭示特大干旱形成演变机理,创新特大干旱下供需双向调控机制,创建具有自主知识产权的特大干旱"监测预警-诊断评估-调控应对"成套理论技术体系和系统装备,在特大干旱全景监测、精确预报、精准诊断和智慧调控方面实现技术突破,更好地支撑干旱预报、预警、预演、预案"四预"措施推进和落实,为我国特大干旱应对实践提供科技支撑.

The drought-limited water level（flow） of a river section is an important indicator of drought in the basin.This can be used as the key basis for starting an emergency response and guiding drought-relief dispatch in water conservancy projects.In this paper, with the aim to examine the related concepts and technical problems of the drought limit water level in the river section, the connotation of the drought limit water level（flow） of the river section is improved.It is the threshold that characterizes the dry state of the river, to determine the water shortage risk and its effect on the social economy and ecological environment.Considering the different degrees of drought and the laws on water use in drought periods, a method for determining the drought limit water level（flow） that is suitable for different types of river sections is proposed from the perspective of grading and staging.The applicability and sustainability of the algorithm for resource use and otherwise constrained river sections are verified with examples from the Lintong section of the Weihe River and the Liaojiawan section of the Fuhe River.This study provides a general algorithm to support flood and drought disaster prevention departments in setting drought limit water level（flow） in river sections and can provide a scientific basis and technical support for drought warning decision-making.

Natural runoff in the Yellow River basin has suffered a sustained decline under the influence of climate change and human activities. Earlier studies mainly investigated the attribution of climate change and human activities, while focusing on the observed runoff decline and rarely on natural runoff, which is not conducive to the efficient utilization and scientific management of water resources in the Yellow River basin. In this study, natural runoff during different periods in the Yellow River basin were evaluated by means of a dualistic water-cycle model, while the contribution of the main factors on the declining natural runoff was elucidated by a multi-factor attribution method. Results revealed that the 1956-2016 annual natural runoff at the Huayuankou station was reduced by 11.46 billion m3 compared to 1956-1979. The contributions of climate change, land-use change, and social water use were estimated to be 24.4%, 25.0%, and 50.6%, respectively. Analysis of the contributions in each Yellow River zone indicated that climate change and human activities were the dominant factors upstream and downstream of Lanzhou, respectively. In order to mitigate the declining trend of natural runoff and promote the ecological protection and high-quality development in the Yellow River basin, stronger measures, such as deep water saving, rigid water control, moderate water increase, efficient water management, and water protection legislation, should be implemented.

在地形条件复杂的高原山区,植被指数并非严格按照经度或纬度的方向呈现条带性变化趋势.本文将经纬度作为组合因子,创新性地提出植被指数空间变化最佳地理轴线的概念,即寻找某一角度轴线,沿此方向植被指数的空间分布具有最显著的条带性特征.本研究以黄河源区植被指数为例,计算黄河源区植被指数空间分布最佳地理轴线,研究表明黄河源区植被指数空间分布沿着西偏北52°轴线具有最显著的条带规律,应用此计算方法对黄河源区植被指数主要影响因子降水量的空间分布规律进行研究,得到降水量的最佳地理轴线是西偏北53°,表明黄河源区植被指数空间分布主要受降水影响,二者在空间上的分布规律基本一致,但植被分布同时还受气温、土壤等因素影响,因此植被指数与降水量的"最佳地理轴线"存在微小差异.

水库旱限水位的合理设置与科学运用对实现水资源安全高效利用、减轻旱灾损失具有重要意义.针对现有方法确定旱限水位时未全面考虑用户对供水保证率、破坏深度的要求,借助优化方法计算而在推广应用时有较高的技术门槛与难度等问题,本文明确了水库分级分期旱限水位定义,以各用户供水保证率最大、最大供水破坏深度最小为目标,构建了旱限水位优化计算模型,提出了旱限水位的多目标优化计算方法;在此基础上,通过分析旱限水位年内变化规律,识别影响供水效果的旱限水位关键时期,提出了一种快速、便捷、适于工程推广应用的旱限水位简便计算方法.结果表明:旱限水位年内变化规律与用水量年内分布规律一致,且高用水时期的旱警水位、枯水期的旱保水位对系统供水目标影响大,为简便计算方法中初步确定旱限水位的反馈调整提供了依据.不设置旱限水位以及按现有方法设置旱限水位,供水系统均发生严重缺水事件,而按本文提出的优化计算方法及简便方法设置旱限水位后,水库可通过提前恰当限制供水,有效避免后续严重缺水事件的发生,使得系统缺水事件发生的几率及严重程度满足设计要求,有效提升了抗旱能力.本文研究为水利部门制定水库旱限水位,指导水库抗旱调度提供了一套优化计算方法及一套科学便捷的方法.

开展水库旱限水位确定技术研究,对于科学指导水库抗旱调度具有重要的意义.因此本文在旱限水位内涵解析的基础上,提出一种水库分级分期旱限水位计算新方法,充分考虑不同的干旱等级、不同行业年内需水过程的差异,采用逆序递推算法得到水库分级分期旱限水位.以山西省张峰水库作为研究对象,计算得到汛期、枯水期、农业灌溉期的旱警水位分别为756.5 m,756.2 m,754.5 m,旱保水位分别为735.8 m,730.7 m,728.2 m.通过方法对比分析,发现新的计算方法能够对更多的行业、更长的时段进行供水改善,在指导水库抗旱调度,提升水利工程群干旱防御能力方面具有显著优势.

在水库分级分期旱限水量确定方法的基础上,将梯级水库进行聚合,提出了聚合水库旱限水量确定方法.以汾河水库和汾河二库为研究对象,将两个水库概化成聚合水库,采用逆序递推的方法确定聚合水库的旱限水量,得到聚合水库在枯水期、农业灌溉期的旱警水量分别为29937万、23945万m3,旱保水量分别为18982万、13501万m3.设置旱限水量后,典型干旱年(1965年6月—1966年5月)生活缺水月数从3个月降低至0,生态和工业缺水月数从5个月降为1个月;生活、工业和生态缺水量降低了2717万m3,农业缺水量增加了641万m3,可以看出旱限水量的制定对跨年干旱起到了调节作用.从各行业整体供水利益角度考虑,农业遭受的损失仍在可接受范围内,缺水量增加不大.旱限水量设置后,可通过小幅减少农业用水量,显著增加干旱年份生活用水和工业用水的供水量.

由于气候变化和人类活动的影响,黄河流域的降雨-径流关系发生了显著性变化,严重影响流域水资源的规划和管理.为了揭示黄河流域降雨-径流关系的变化特征、趋势及主要驱动因素,研究采用Mann-Kendall检验、双累积曲线法、Copula函数、累积量斜率变化率法分析1960-2010年黄河流域的径流系数时空变化规律、7个主要区间降雨-径流关系的突变年份、降雨径流组合概率变化,以及气候变化和人类活动对降雨-径流关系变化的贡献率.结果表明:黄河全流域降雨-径流关系有明显的趋势性变化,其中除黄河源区的径流系数没有明显变化及少数地区的径流系数有增大的趋势外,绝大部分地区的径流系数有明显减小的趋势;黄河流域7个主要区间,即唐乃亥以上、唐乃亥—兰州、兰州—头道拐、头道拐—龙门、龙门—三门峡、三门峡—花园口及花园口—利津的降雨-径流关系突变年份依次为1989、1984、1997、1979、1992、1987和1970年,年份差异主要受到人类活动时间的影响,流域内大规模水土保持措施开展的年份、水利工程的兴建时间都是造成降雨-径流关系发生转折的重要因素;黄河流域主要区间降雨-径流关系发生转折后,同等降雨条件下其产流能力降低;人类活动是降雨-径流关系变化的主要驱动因素,贡献率均在50％以上,且越往下游,影响越大.

干旱指数适用性问题是当前干旱研究中的热点问题.本文基于标准化降水指数(SPI),标准化降水蒸散指数(SPEI)和降水Z指数(CZI)等传统标准化干旱指数,以线性组合方法构建综合气象干旱指数(linear combination synthesis drought index,LSDI),提出混淆矩阵评价方法对所有气象干旱指数的适用性进行比选分析,并在鄱阳湖流域加以应用.研究表明:(1)LSDI指数与标准化干旱指数的准确率和精度的季节性均值近似相等,但LSDI指数召回率和综合评价指标F1-Score的季节性均值更高.LSDI指数能够像标准化干旱指数一样很好地捕捉到干旱事件,同时具备三个标准化干旱指数表征干旱的优势,对干旱事件识别的效果更好.(2)鄱阳湖流域干旱强度未来趋势:夏季和冬季表现为下降趋势,干旱情况有所缓解,春秋季表现为上升趋势,干旱情况有所加重.(3)鄱阳湖流域夏季和秋季干旱发生频率高,频率范围在30％～40％.干旱发生频率呈现赣南较低,赣北较高的空间分布形式.(4)鄱阳湖流域易发生全域性和局域性干旱,夏季和秋季干旱发生范围存在不显著上升趋势;春季和冬季干旱发生范围存在不显著下降趋势.

本文基于精细化水资源配置模型(GWAS),通过对河流的生态需水断面作为生态单元在模型中进行概化,将生态控制目标纳入水资源调配系统,使多种水源与社会经济单元、生态单元之间建立联系,设定相应的约束条件,实现多目标的长系列模拟过程,达到面向河道断面生态流量保障的分布式调配的目的.以深圳市坪山河流域为例开展河流生态调度研究,划定了生态环境需水单元及经济社会单元,统筹考虑流域内水库、污水处理厂、再生水厂等多种供水节点,基于GWAS模型开展各断面生态需水计算,识别了现状条件下各断面生态流量保障程度,确定了水库、再生水联合补水方案,最终显著提高了各个断面生态流量保障程度.GWAS实现了对传统水资源配置模型进行功能扩充,在流域层面实现用水与河道生态流量统筹协调计算的生态调度,一方面发挥水资源配置模型的精细化和分布式特点,另一方面统筹协调经济社会与生态的用水需求,进行多水源调配以满足不同用水对象的需求,对开展流域综合治理,制定流域生态补水方案具有重要意义.