Study region: The Yellow River Basin (YRB) in China. Study focus: Efficient, equilibrial, and sustainable water allocation is essential for socio-economic development and ecological stability, especially in water-scarce regions. This study proposes a multidimensional assessment framework integrating development efficiency, spatial equilibrium, and temporal sustainability. Efficiency and equilibrium indicators, based on population, GDP, irrigable farmland, and urbanization, reflect regional development levels and disparities. The sustainability indicator, coupling water supply utility with the theory of sustainable orientation, assesses long-term stability across six dimensions: existence, effectiveness, freedom, adaptability, security, and coexistence. New hydrological insights for the region: The evaluation results of water allocation schemes under different scenarios in the YRB demonstrate that the framework can identify and reflect the impacts of changing conditions on water allocation, showing strong stability and sensitivity. The development efficiency, spatial equilibrium, and temporal sustainability exhibit dynamic relationships, without absolute trade-offs or synergies. Increasing water availability can effectively improve development efficiency and temporal sustainability, albeit with a slight reduction in spatial equilibrium. In contrast, blindly raising in-stream ecological water use under scarcity can significantly reduce development efficiency. Adjusting industrial (water use) structure and improving water use efficiency are key to achieving efficient, equilibrial, and sustainable basin development. The framework holds broad potential for application in water-scarce basins worldwide, supporting more balanced and resilient water resource management across diverse socio-economic and ecological contexts.

Abstract Flash drought (FD), so‐named for its abrupt and unforeseen onset, poses a significant challenge to forecasting, as current Numerical Weather Prediction (NWP) shows limited skill in the sub‐seasonal to seasonal timescale (S2S, 2‐week to 2‐month range). Here, we present various data‐driven deep learning (DL) frameworks designed to bridge this S2S FD forecasting gap and uncover underlying drought‐inducing mechanisms via interpretability. We developed multiple spatiotemporal DL models (e.g., ConvLSTM, U‐Net) and a Bayesian model averaging (BMA) ensemble to forecast pentad‐scale (5‐day) Standardized Soil‐moisture Index (SSI), serving as the basis for subsequent FD identification. These models leverage diverse drought‐related precursors, including compound drought‐heatwave, evaporative stress, vapor pressure deficit (VPD), and vegetation conditions. Evaluating performance across basins with varied climate regimes, we found that Artificial‐Intelligence‐based methods offer enhanced SSI forecast reliability over NWP, particularly for weather‐scale (1–3 pentads). Notably, the BMA ensemble provided reliable SSI forecasts up to 12 pentads (∼60 days, spanning the entire FD lifecycle), outperforming advanced physics‐based NWP and pixel‐wise benchmark models. Occlusion heatmap reveals that DL models leverage physically plausible precursors for predicting subsequent FD events. Through SHAP analysis, three primary FD‐inducing patterns were identified: water‐dominated (e.g., precipitation), energy‐dominated (e.g., VPD), and multi‐driver composite. Representative regions are arid climate, snow climate, and near‐equatorial areas (e.g., equatorial and warm climate), with widespread interactions among drivers. This study demonstrates explainable DL models potent tools for advancing SSI forecasting and dissecting complex hydro‐climatological drivers relevant to FD assessment, offering novel insights for improved early warning systems.

Runoff change directly alters the spatiotemporal distribution of available water resources and disrupts the dynamic balance between water supply and demand, leading to seasonal or even persistent water scarcity in arid inland river basins. This study aims to improve the adaptability of basin water resources systems to runoff change. Therefore, an adaptive water resources management framework is developed, comprising a joint optimal operation model for reservoirs and ponds, a water resource spatial equity allocation model, and integrated adaptive management strategies encompassing water supply security, water loss control, and water-use coordination. The reservoir operation model and the water resources allocation model are coupled to evaluate the impacts of runoff change on the water supply process and to analyze the characteristics and major influencing factors of basin water scarcity. Adaptive management strategies are then implemented stepwise to evaluate their combined effects on reducing the frequency, duration, and severity of water shortages. The framework is applied to the three major source basins of the Tarim River Basin in northwestern China, namely the Aksu River Basin, Hotan River Basin and Yarkant River Basin. The results show that implementation of the adaptive management strategies increases water supply reliability in the above three basins from 0.25, 0.11, and 0.58 to 1.00, respectively. This study provides methodological support and decision-making references for adaptive water resources management in arid inland river basins.

Rational water resources allocation is crucial for achieving the synergistic development of the water-ecology-economy (WEE) nexus in arid basins. Quantitative assessment of individual water users’ benefits under different water shortage rates provides a robust basis for allocation strategies. This study clarifies the pairwise coupling relationships between the water system and other subsystems using a growth curve function. These relationships are integrated as efficiency functions into a multi-objective water resources allocation model that simultaneously optimizes economic benefits, ecological benefits, carbon sequestration, and spatial equilibrium. The water supply volumes allocated to four vegetation types are designated as decision variables. Four scenarios are evaluated: ecological priority, economic priority, balanced optimization, and comprehensive benefit maximization. Allocation performance is assessed using the coupling coordination degree (CCD) method. This research takes the Tarim River Basin, a typical arid basin, as a case study. Key findings reveal that "S"-shaped and "J"-shaped nonlinear relationships exist between crop growth decay rates and water shortage rates. To avert significant losses, it is advisable to maintain water shortage rates below the first inflection point. Notably, most sub-basins perform optimally under the comprehensive benefit maximization scenario, exhibiting the highest CCD in the WEE nexus. These findings provide scientific guidance for both efficient water resource utilization and sustainable development of the WEE nexus in arid basins.

Mountain glaciers play a critical role in freshwater supply and hydrological regulation. Climate warming is projected to accelerate glacier melting in High Mountain Asia, threatening water resource sustainability, particularly in the arid and semi-arid regions. This study employs the integrated ice-dynamic Open Global Glacier Model to investigate glacier responses to past and future climate change. The annual mass balance series of 11,625 glaciers from 1990 to 2019 is reconstructed, revealing their spatiotemporal variability in alpine regions. Additionally, the long-term dynamics of glacier mass, area, and volume are assessed through 2100 under different climate scenarios, focusing on glacier runoff changes and the differences in the timing of peak runoff. Finally, the unit area service pricing method is applied to establish an index for quantifying the ecological value loss resulting from glacier retreat. The results show that climate warming will lead to substantial and irreversible mass loss. This process is characterized by initial thinning followed by retreat, resulting in an overall negative mass balance. By the end of the 21st century, glacier area and volume will decrease by more than 40% in most basins, with peak runoff expected around 2050 under low-emission scenarios. In contrast, delayed peaks are generally associated with high-emission scenarios and regions with substantial glacier reserves. Glacier service values are predicted to decline significantly or be entirely lost, with this trend intensifying from southwest to northeast in the Tarim River Basin. This study provides new insights into glacier dynamical and hydrological responses under climate warming, contributing to regional socio-ecological sustainability and optimized water resource management.

Droughts occur frequently and are highly destructive in arid and semi-arid regions, and their spatiotemporal evolution becomes increasingly complex with climate warming and intensified human activities. Conducting research on the spatiotemporal evolution characteristics and influencing factors of agricultural drought in major grain-producing areas is of vital importance for responding to food crises and supporting the development of characteristic agriculture in the arid regions of northern China. Therefore, this paper took the Yellow River Basin in arid regions, semi-arid regions, and the transitional zone between humid and semi-humid regions as an example and used trend test, run length theory, and standard soil index (SSI) methods to reveal the spatiotemporal distribution characteristics and evolution laws of multi-scale agricultural drought. 17 extreme climate indexes and analysis of variance (ANOVA) methods were used to quantitatively reveal the impact of droughts. The results show that as the time scale increases, the frequency of agricultural droughts decreases, but the duration and intensity of the droughts significantly increase; The degree of multi-scale agricultural aridification has undergone a significant change around the 90a. Before 90a, different climate zones show an overall trend of warming and humidification, while the trend has been opposite since then, and severe agricultural droughts are concentrated in this period. Meanwhile, from the upper reaches to the lower reaches of the Yellow River, some extreme precipitation index detection values show an increasing trend, but the extreme temperature index has the opposite explanatory power. The spatial differences of extreme climate indexes will exacerbate the spatial heterogeneity of agricultural droughts over multiple time scales. As the time scale increases (from SSI-1 to SSI-12), the likelihood of extremely severe or extreme droughts increases significantly at the 95% confidence level. At different time scales, the contributions of extreme precipitation and temperature indexes to agricultural droughts in various climate zones vary significantly. Among them, Rx1day and Rx5day are the core driving factors, and in some regions, their explanatory power for multi-scale agricultural droughts is as high as over 90%. These research results provide important practical guidance for optimizing agricultural production distribution, safeguarding food security, and developing drought early warning systems and countermeasures in China's Yellow River Basin.

The water-energy-food-carbon (WEFC) nexus in drylands faces governance challenges due to the lack of quantitative frameworks for resolving synergy-tradeoff conflicts among Sustainable Development Goals (SDGs). We expand the WEFC framework by integrating seven SDGs across socioeconomic, ecological, and resource dimensions, thereby overcoming single-dimension limitations. Socioeconomic-environmental feedbacks are incorporated into the nexus. Impulse response analysis is employed to capture dynamic SDG interactions, moving beyond the static paradigm of conventional coupling coordination studies. By conceptualizing the nexus as a dynamic interconnection among seven SDGs, we develop a WEFC assessment index towards SDGs (WEFC-SDGI) to address inconsistencies in SDG evaluation. From 2000-2023, WEFC-SDGI in global drylands increased significantly at an annual rate of 1.95 (p < 0.05). However, only 37.1% of countries are projected to achieve the 2030 targets. The synergy and trade-off network highlights adaptive water-centric policies as pivotal, generating cascading benefits for energy security, food systems, and climate resilience. Our framework proposes diversified development pathways for global drylands to reconcile resource scarcity with accelerated SDG implementation and support progress toward the 2030 Agenda.

Pumped storage hydropower plants (PSHPs) in China have recently begun participating in inter-provincial medium- and long-term (IPMLT) markets. However, the effective utilization of their regulation potential is currently hindered by rigid, fixed-path trading mandated by the administrative two-part tariff system. This "point-to-point" isolation prevents PSHPs from establishing competitive relationships across a broader geographical scope, leading to underutilization of their wide-area regulation capabilities. To bridge this gap, we propose an inter-provincial multi-channel centralized bidding framework specifically designed for the spatiotemporal coupling characteristics of PSHPs. This framework integrates three novel components: (1) two centralized clearing models developed to decouple the pumping and generation processes, establishing a multichannel trading mechanism that maximizes PSHP's arbitrage revenue; (2) a decomposition and pairing method designed to apply merit-order matching to preliminary cleared energy, reconciling operational constraints with market economics in the final clearing results; (3) a multi-stage security verification strategy devised to precisely identify and curtail infeasible energy, thereby avoiding the over-curtailment inherent in pro-rata methods. The proposed framework is validated through a case study of the Zhen'an PSHP in China, demonstrating its capability to ensure physical feasibility while improving rescource allocation efficiency.

Inter-basin water transfer (IBWT) projects represent one of the most effective approaches to alleviating water scarcity caused by the uneven spatiotemporal distribution of water resources. However, the long-term sustainability of these projects critically depends on scientific regulation. Beyond addressing the inherent trade-offs between fairness and efficiency, IBWT projects must be systematically coordinated with existing cascade reservoirs in the receiving basin, rather than functioning in isolation. To this end, this study develops a nested two-layer coordinated regulation framework that integrates fairness and efficiency for IBWT projects and cascade systems. This model is applied to Phase I of the South-to-North Water Transfer Western Route (SNWT-WI) in the Yellow River Basin (YRB). Three scenarios—Basic (without the SNWT-WI), SO (standalone operation), and CO (coordinated operation)—were established for comparative analysis. Compared to the SO scenario, the CO scenario demonstrates significant advantages in securing regional water supply. Although it involves minor trade-offs regarding in-stream ecology and total power generation, the CO water transfer process is substantially more flexible. This flexibility provides superior adaptability to hydrological variability and aligns more closely with the current socio-economic development demands of the YRB. Nevertheless, the augmented inflow from the SNWT-WI increases spillway discharge, presenting a new operational challenge for existing cascade hydroelectric stations. Overall, the proposed coordinated regulation model demonstrates broad applicability, offering valuable methodological insights for the sustainable management of large-scale IBWT projects worldwide

Intensified drought significantly shifts the structure and function of the ecosystem, driving asynchronous changes between them. However, understanding the relationship between terrestrial ecosystem responses to drought and vegetation growth remains a persistent challenge due to limited direct observations. Here, we used gross primary productivity as a proxy for carbon sink, the normalized difference vegetation index for canopy structure, and the standardized ecological water shortage index to disclose this relationship across 24 ecological-climatic regions and 6 vegetation types. Integrating climate, vegetation, soil, and topography factors, the ecological-climatic regions were classified using Fuzzy C-Means method combined with the ant colony algorithm. The results indicated that 55.7 % of the vegetated areas in the Yangtze River Basin (YRB) have experienced inconsistent vegetation growth in canopy structure and the ecosystem carbon sink. More than 66 % of vegetated areas displayed short-term (<= 3 months) responses to ecological drought. Notably, forest ecosystems showed much longer lagged responses, with mean NDVI lag time exceeding 7 months in significantly decreasing regions. The ecosystem carbon sink is more sensitive to ecological drought than canopy structure. Grassland is the most sensitive vegetation type in the YRB, and forests express the most pronounced ecological drought impacts. Generally, vegetation in arid regions is more sensitive to ecological drought than in humid areas. Ecosystem carbon sink in areas of increased growth shows greater sensitivity to ecological drought than in areas of decreased growth. Furthermore, across 9 vegetation growth pattens between ecosystem carbon sink and canopy structure, the sensitivity of ecosystem carbon sink and canopy structure to ecological drought also varies distinctly. The lowest sensitivity of vegetation to ecological drought was observed when ecosystem carbon sink declined, and canopy structure increased within the YRB.

The operation of hydropower plants must balance multiple demands. Specifically, plant operators prioritize economic benefit. Grid managers require enhanced peak-shaving capability to address source-load uncertainty. Basin managers focus on reservoir safety to prevent overtopping accidents. Coordinating these objectives is particularly challenging for weakly regulated cascade hydropower plants(WRCHP), which consist of multiple adjacent plants with limited regulation capacity. This study proposes a multi-objective bilevel risk-economic dispatch model. At the plant level, economic benefit is quantified by combining electricity revenue and ancillary service compensation, while peak-shaving capability is evaluated using a CVaR-based residual load variance risk metric. Furthermore, a method for calculating emergency time based on the dynamic control of daily maximum water level is proposed to quantify dam safety margins against overtopping. At the unit level, the model minimizes water consumption and avoids unit vibration zones. The model is applied to the ZM and JC hydropower plants in the YZ River basin. Results reveal trade-offs among economic benefit, peak-shaving capability, and overtopping risk, and identify key influencing factors such as plant output, forebay level, generation head, and grid load. In addition, this study also summarizes dispatching strategies for WRCHP under multi-objective coordination, providing valuable guidance for operators.

The rapid expansion of wind and photovoltaic energy has significantly driven the growth of pumped-storage hydropower plants (PSHP). As a prominent PSHP configuration, pump-back PSHP (PSHPPB) utilizes cascade in-stream reservoirs from conventional hydropower plants (HP) by integrating reversible pump-turbines technology. However, this configuration imposes considerable operational pressure on cascade reservoirs, necessitating a delicate balance between fulfilling water supply demands, managing PSHPPB pumping and generation cycles, and maintaining conventional HP output. This study: (1) investigates the coordinated operation of PSHPPB-HP system to enhance photovoltaic (PV) power integration under water supply priorities; and (2) evaluates the optimal PV capacity that can be integrated into the PSHPPB-HP system, accounting for long-term basin-scale water supply variability. A case study of the PSHPPB located in the upper Yellow River Basin of China, utilizing the cascade reservoirs of Longyangxia (LYX) and Laxiwa (LXW) hydropower stations, is presented. Results indicate that: (1) an increase in the daily average release from the LYX reservoir shifts the PSHPPB operation from a pumping-generating mode to a generation-only mode; (2) energy consumption of the PSHPPB decreases to zero as the daily average reservoir release increases, while its power generation follows a distinct dip-and-climb pattern; (3) two critical daily average reservoir release thresholds, approximately 900 m3/s and 1500 m3/s, are identified for optimizing the PV integration in the PSHPPB-HP system; (4) the PSHPPB-HP system can support up to 4141.6 MW of PV capacity (62% of the total installed capacity of the PSHPPB-HP system) with PV curtailment limited to 5%, accounting for long-term water supply variability in the Yellow River Basin. These findings provide valuable insights for PSHPPB planning and operation, not only in the Yellow River Basin but also in other global regions.

Socioeconomic drought is essentially a supply–demand imbalance, yet the cumulative water stress generated by this imbalance remains insufficiently quantified in human-modified river basins. This study proposes a non-stationary assessment framework by integrating the GAMLSS model, Copula functions, and Bayesian conditional probability inference, using the lower Yellow River basin (1980–2022) as a case study. We introduce the Socioeconomic Drought Potential Vulnerability Threshold (SEDVT) to quantify the "initial risk load"—defined as the maximum Antecedent Cumulative Water Deficit (ACWD) a system carries at the moment of drought onset. The Drought Resistance Capacity (DR) is further evaluated using the ratio of Conditional Return Periods. The findings reveal: (1) A significant regime shift in drought patterns occurred, with the frequency of severe and extreme droughts decreasing by nearly 40

Cascade development is a key approach for modern hydropower utilization. However, differences in ownership and scheduling authority lead to multiple operation modes in cascade hydropower plants, including cooperative scheduling (CSM), game-based scheduling (GSM), and independent scheduling (ISM). These modes influence both operational efficiency and the accommodation of wind and PV, thereby affecting the power system's carbon reduction potential. This study proposes a framework to evaluate carbon reduction benefits under different scheduling modes. A load generalization method is developed to capture daily variability and peak shaving, based on which a multi-energy complementary carbon reduction model (MECR-PS) is established. Using the LYX, LXW, and NN cascade hydropower plant as a case study, the results show: (1) CSM improves carbon reduction benefits by 3.5 % compared to ISM and GSM. (2) GSM benefits upstream plants, while ISM favors downstream plants. (3) Wind generation and hydropower discharge are positively correlated with carbon reduction. (4) Under high-flow conditions, GSM for the upstream, ISM for the midstream, and CSM for the downstream plants yield the highest individual power generation. Under other conditions, CSM consistently delivers the highest generation across all plants. These findings offer valuable insights for cascade hydropower operation and lowcarbon power system development worldwide.

In the joint operation of parallel reservoir systems, it is possible to effectively coordinate and compensate for water supply among reservoirs by utilizing hydrological characteristics, reservoir regulation capabilities, and geographical differences. However, the rules for joint operations of parallel reservoir systems are complex when the multiple reservoirs supply water to one user with multiple demands (such as the agricultural and ecological demand). The object of this study is proposing a set of compensation operating rules to address the above issues. The set of rules include the reservoir sequential compensation operating rule, the partial compensation operating rule, and the dynamic compensation operating rule. The rules are extracted with a case study of the parallel reservoir system of the Hotan River Basin (HRB), China. The parallel reservoir system of HRB include two largescale reservoirs and sixteen small-scale reservoirs. The results indicate that all three type rules could realize the hydrological and reservoir capacity compensation of the parallel reservoir system. The reliability of joint water supplies reaches 100%, while the reliability of individual water supplies is 50%, 54%, and 64%, respectively under the above three operation rules. Considering the characteristics of runoff and the reservoir, the reservoir dynamic compensation operating rule allocate the water resources with the joint water demand of each user in each period. And the dynamic compensation operating rule improves the reliability of water supply. This indicates that the rule successfully addresses the water demand for various users, bridging the gap between supply capacity and joint demand. It is suitable for extreme hydrological conditions and widely applicable.

The sensitivity of snow and glacier melt processes in alpine mountains to climate change, along with the variations in snow and glacier distribution with elevation, can significantly affect runoff and its components. However, the influence of climate and elevation on runoff component changes remains unclear. This study employs the Spatial Processes in Hydrology (SPHY) model, incorporating a multi-stage calibration method for snowmelt, glacier melt, and confluence, using data from MODIS and GRACE satellites. The aim is to quantitatively analyze runoff components in the Tarim River Basin's four source streams and reveal the impacts of climate and elevation changes on runoff and its components. Results indicate that runoff in the four source streams is primarily recharged by snow and glacier meltwater at high elevations and rainfall at lower elevations. The Hotan and Yarkant Rivers are mainly glacier melt runoff, while the Aksu and Kaidu Rivers are mainly rainfall runoff. Runoff increasing for glacier melt-dominated rivers occurs at high elevations (3500-5000 m) and ultrahigh elevations (>5000 m), whereas runoff increases for rainfall-dominated rivers occurs at middle elevations (2000-3500 m). Temperature and precipitation positively impact water resources in the four source streams. Specifically, a 10 % temperature increase during summer results in a 7.2 %, 6.5 %, 4.7 %, and 4.4 % increase in total runoff, while a 10 % precipitation increase causes a 2.7 %, 3.8 %, 5.0 %, and 5.5 % increase in runoff. Precipitation mainly affects the Aksu and Kaidu Rivers' discharge, whereas temperature mainly affects the Hotan and Yarkant Rivers. This study provides a reference for understanding hydrological processes in similar environments, which is crucial for researching alpine mountain hydrology under climate change.

The expansion of wind and solar energy necessitates the development of pumped-storage hydropower plant (PSHP). Integrating open-loop PSHP (OL-PSHP) with its in-stream reservoir-based hydropower plants (HP) results in a cooperation mode that is significantly more intricate than traditional closed-loop PSHP. With a focus on OL-PSHP, the primary goal of this study is three-fold: (1) derive the various peak shaving modes for OL-PSHP and HP and propose the corresponding cooperation model between them; (2) determine the optimal initial water level and daily average release from the OL-PSHP in-stream reservoir to maximize the OL-PSHP-HP peak-shaving benefit; (3) quantify the impact of OL-PSHP operations on intraday water level fluctuations and power output of the in-stream reservoir system. WaRang OL-PSHP located in the upper Yellow River Basin of China, relying on Laxiwa (LXW) in-stream reservoir, is selected as the case. Our findings suggest that: (1) OL-PSHP can operate in various modes to accommodate intraday fluctuations in renewable generation and load demand, including sequential pumping followed by generation, initial generation followed by pumping, or hybrid mode with alternating pumping/generation cycles within a single day. (2) Recommended initial daily water levels for the WaRang OL-PSHP upper and lower reservoirs are all approximately halfway between the dead water level and normal water level. The optimal daily average outflow of the LXW reservoir is suggested to be kept around 700 m(3)/s, with this value varying according to the operational modes of OL-PSHP. (3) The OL-PSHP exacerbates the daily fluctuations in the LXW reservoir water levels, resulting in a maximum daily decrease of 0.77 m and a maximum increase of 0.37 m. The annual power output of the LXW HP could increase by up to 547 x 10(4) kWh or decrease by up to 2312 x 10(4) kWh, representing approximately 0.06 and 0.26 % of the LXW HP's average annual generation, respectively. These findings can offer valuable insights for the cooperation of OL-PSHP-HP located in other basins worldwide.

Plain reservoirs are critical to water allocation in arid regions due to their low cost and proximity to irrigation areas. However, its remarkable evaporation and seepage losses exacerbate the water resources shortage in arid regions. Therefore, mountain reservoirs present a superior alternative to plain reservoirs owing to their low water loss. This study proposes a joint operational model of mountain and plain reservoirs in arid inland river basin to quantify the potential capacity reduction of plain reservoirs. The Aksu River Basin in China is selected as a case study to evaluate the feasibility of replacing plain reservoir capacity with mountain reservoirs. The results show that mountain reservoirs increased the guaranteed irrigation water supply rate by 18.3 % in the planning year, while reducing the utilization of plain reservoirs. Additionally, the mountain reservoirs tend to store water with priority during high-flow periods, thereby reducing the water storage volume in plain reservoirs. By contrast, plain reservoirs supply water preferentially during periods of deficit. Worthy of note is that, mountain reservoirs still have considerable available storage. In this context, plain reservoirs can be reduced by 1.74 x 108 m3 (74.04 %) in the planning year, saving 0.32 x 108 m3 of water. By comparison, the plain reservoirs should remain unchanged in the current year. In summary, reducing the storage capacity of plain reservoirs in arid basin is conducive to lowering evaporation and seepage losses. This study provides a high-efficient way of utilizing water resources utilizing in arid regions from the viewpoint of reservoir capacity replacement in mountain-plain reservoir systems.

The integration of pumped storage (PS) within cascade hydropower plants (HPPs) managed by different entities to form a multi-operator hybrid pumped storage hydropower (MOHPSH) system is a crucial strategy for enhancing energy system flexibility. However, this system faces significant operational challenges from its bidirectional hydraulic coupling and the conflicting interests of multiple operators. Previous research has predominantly modeled such system under a single-entity assumption, overlooking the coordination complexities among diverse operators. To conquer the issue, this study develops a coordinated scheduling framework encompassing independent, partially joint, and complete joint schedule modes. Through this framework, we clarify operator interaction mechanisms within the MOHPSH system, identify key factors limiting system peak regulation performace, and provide strategic guidance for the selection of operation modes. Applied to a MOHPSH system on the Han River, the results reveal that: (1) system power generation benefits show limited sensitivity to the choice of operation modes, whereas peak regulation performance is significantly dependent on it; (2) the MOHPSH system's peak regulation performance is primarily constrained by the downstream XY's limited regulatory capacity and suboptimal inter-operator operational prioritization, leading to a loss of peak regulation water volume at XY, which can be as high as 28.7 %; and (3) a critical threshold is identified at an XY initial water level of 240.8 m. Below this level, system operational flexibility is high (excluding mode M4, the PSpriority mode), but above it, the complete joint schedule mode M5 becomes essential to overcome the XY reservoir capacity bottlenecks.

Multi-energy complementary technology has become one of the core elements to promote the structural transformation of global energy and cope with climate change. Faced with the rapid growth of wind power and photovoltaic, the uncertainty of its power generation will increase further, and it is urgent to explore more types of flexible regulation power sources to compensate for them. The construction of pumped storage power stations among cascade reservoirs is a feasible way to expand the flexible resources of the multi-energy complementary clean energy base. However, this way makes the hydraulic and electrical connections of the upper and lower reservoirs more complicated, which brings more uncertainty to the power generation. Hence, to support the high-quality power supply, this research explores the complementary characteristics of the clean energy base building different types of pumped storage power stations, and recognizes the efficient operation intervals of the giant cascade reservoir. First, a multi-dimensional uncertainty evaluation system is proposed to elaborate on the typical output scenarios of wind power and photovoltaic in more detail. Next, based on different utilization principles of wind power and photovoltaic, the multi-energy complementary operation models of the hydropower-wind-PV hybrid system, the hydropower-wind-PV hybrid system including pump stations, and the hydropower-wind-PV hybrid system including reversible hydro units are established. Further, a multi-dimensional scenarios random combination method is applied to investigate the response relationship between the operation parameters of the key reservoir and the operation indicators of the clean energy base. Finally, these above methods have been practiced in the clean energy base in the upper Yellow River basin. The main results of the research are as follows: (1) when the power output of wind-PV plants is high, the absorption rates of wind power and photovoltaic increase by 36% and 12% respectively, in hydropower-wind-PV hybrid systems with reversible hydro units and with pump stations, compared to the hydropower-wind-PV hybrid system; (2) when the power output of wind-PV plants is high, the load loss rates of the transmission channel decrease by 28.57% and 14.28% respectively, in hydropower-wind-PV hybrid systems with reversible hydro units and with pump stations, compared to the hydropower-wind-PV hybrid system; (3) for the hydropower-wind-PV hybrid system including reversible hydro units, the comprehensive utilization flow of the key reservoir respectively maintain 500-800 m3/s and 1000-1200 m3/s in the max scenario and min scenario of wind power and photovoltaic, which is beneficial to the efficient absorption of new energy and high-quality power transmission; (4) for the hydropower-wind-PV hybrid system including pump stations, the comprehensive utilization flow of the key reservoir should respectively keep 500-750 m3/s and 950-1100 m3/s in the max scenario and min scenario of wind power and photovoltaic.