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Reducing river flows significantly affects livelihoods, ecology and industrial production. Therefore, allowing for ecological flow requirements has been applied to limiting human water consumption and is incorporated into water allocation planning. However, the unavailability of ecological data greatly limits e‐flow studies and this lack of sufficient ecosystem data is mostly addressed by using hydrological metrics as surrogates of the river ecosystem. This study employed the nine indicators of the 'Flow Health' model to assess river hydrological health and explore optimal ecological flow regimes. The modelling estimated the required flow and the extra flood flows of ecosystem conservation under default and custom thresholds. Ecological flows were calculated for five stations of the Weihe River through coupling with three hydrological methodologies. The index of flow deviation indicated that the flow regimes in Weihe River have partially changed from the reference period. Fish and other aquatic habitats have changed by reduced flows, but the health of the floodplain ecosystem has not been seriously affected. The ecological flow modelling results showed that the extra flow required for the ecology restoration in five stations is concentrated from July to September. The optimal ecological flows in dry seasons by coupling three hydrological methods were less than the average current flow, which is reasonable. This coupling provides ideas on how environmental flow assessments are undertaken in similar regions. [ABSTRACT FROM AUTHOR]

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The efficient operation of multi-reservoirs is highly beneficial for securing supply for prevailing demand and ecological flow. This study proposes a monthly hedging rule-based aggregation–decomposition model for optimizing a parallel reservoir system. The proposed model, which is an aggregated hedging rule for ecological flow (AHRE), uses external optimization to determine the total release of the reservoir system based on improved hedging rules—the optimization model aims to minimize water demand and ecological flow deficits. Additionally, inner optimization distributes the release to individual reservoirs to maintain equal reservoir storage rates. To verify the effectiveness of the AHRE, a standard operation policy and transformed hedging rules were selected for comparison. Three parallel reservoirs in the Naesung Stream Basin in South Korea were selected as a study area. The results of this study demonstrate that the AHRE is better than the other two methods in terms of supplying water in line with demand and ecological flow. In addition, the AHRE showed relatively stable operation results with small water-level fluctuations, owing to the application of improved hedging rules and a decomposition method. The results indicate that the AHRE has the capacity to improve downstream river ecosystems while maintaining human water use and provide a superior response to uncertain droughts. [ABSTRACT FROM AUTHOR]

Since hydrotechnical is a broad topic, the peer review process is extremely important in maintaining the quality and validity of technical government regulations. Peer review is necessary to improve government technical regulations in the hydrotechnical field, as it is observed from ISI articles on some of these regulations which are characterized by eclecticism. A primary challenge in peer review is finding specialists who are capable of reviewing technical documents. This challenge is also relevant regarding government regulations. Solutions to this challenge include maintaining a database of academic specialists, incentives to participate, and encouraging collaboration between agencies and academic institutions. Disclosure of the reviewers’ identities and the provision of guidelines for the review process of technical regulations should be a priority of the relevant authorities, as it would promote transparency. Regulations should be designed as adaptable and responsive to changes and new information in ored to address the dynamic nature of hydrotechnical issues. [ABSTRACT FROM AUTHOR]

This study analyzed 61 years of hydrological data from the Minhe and Xiangtang Hydrological Stations (1956–2016) to examine hydrological changes and ecological flow assurance rates in the Huangshui River Basin, China. Using the Mann–Kendall trend test, IHA/RVA method, and ecological flow calculation methods, the study revealed the following results: (1) After 1994, increased human activity in the Datong River led to a measured runoff decrease compared to natural runoff. Although human activities in the Huangshui River's main stream were present before 1972, after 1972, these activities intensified, resulting in a more pronounced decrease in the measured runoff. (2) Ecological flow analysis indicated that the main stream of the Huangshui River and the Datong River have ecological flow assurance rates of 100% for all but a few months, where the rates are 98%. The water volume is sufficiently abundant to meet ecological water demands. [ABSTRACT FROM AUTHOR]

In order to safeguard the health of river ecosystems and maintain ecological balance, it is essential to rationally allocate water resources. This study utilized continuous runoff data from 1967 to 2020 at the Zhouqu Hydrological Station on the Bailong River. Five hydrological methods, tailored to the hydrological characteristics of the Zhouqu hydrological cross-section, were employed. These methods included the improved dynamic calculation method, the NGPRP method, the improved monthly frequency computation method, the improved RVA method, and the Tennant method. Ecological flow calculations were conducted to determine the ecological flow, with analysis carried out through the degree of satisfaction, economic benefits, and the nonlinear fitting of the GCAS model. We established an ecological flow threshold and early warning program for this specific hydrological cross-section. Ecological flow values calculated using different methods for each month of the year were compared. The improved RVA method and Tennant method resulted in small values ranging from 4.05 to 36.40 m3/s and 7.65 to 22.94 m3/s, respectively, with high satisfaction levels and economic benefits, but not conducive to ecologically sound development. In contrast, the dynamic calculation method, NGPRP method, and improved monthly frequency calculation method yielded larger ecological flow values in the ranges of 21.79–97.02 m3/s, 23.90–137.00 m3/s, and 28.50–126.00 m3/s, respectively, with poor fulfillment and economic benefits. Ecological flow thresholds were determined using the GCAS model, with values ranging from 16.72 to 114.58 m3/s during the abundant water period and from 5.03 to 63.63 m3/s during the dry water period. A three-level ecological warning system was proposed based on these thresholds, with the orange warning level indicating optimal sustainable development capacity for the Zhouqu Hydrological Station. This study provides valuable insights into the scientific management of water resources in the Bailong River Basin to ensure ecological security and promote sustainable development. [ABSTRACT FROM AUTHOR]

Objective: As part of a large‐scale hydroelectric project, the mean annual flow of the Rupert River (northern Quebec, Canada) was reduced by 52% at its mouth in 2009. To protect fish habitat, an ecological flow regime that was modulated according to the biological seasons was implemented downstream from the diversion point. An 8‐year monitoring program, including 2 years before partial diversion, was carried out to verify the effectiveness of this mitigation measure on the total annual abundance of anadromous Coregoninae (Cisco Coregonus artedi and Lake Whitefish C. clupeaformis) larvae, which was used as biological indicator of recruitment success. The monitoring also aimed to determine the effects of flow modification on the timing of the larval drift and the spatial distribution of larvae in a river cross section. Methods: Each year, sampling consisted of installing drift nets during the entire downstream larval migration in a river cross section of the lower Rupert River. Drift nets were systematically placed to ensure representative sampling of the river section. Result: Prior to flow reduction, the estimated total number of larvae varied between 1.8 and 8.6 million. Over the following 6 years, the estimated larval population has remained steady at 3–4 million. Otherwise, larval drift characteristics have not changed since the flow reduction, as (1) the duration of the larval drift is the same as before, about 1 month in May and early June, with a peak period of about 8 days; (2) rise in water temperature in spring is a determining factor in the timing of larval drift; and (3) the larvae drift mainly near the surface of the water. Conclusion: The monitoring results indicate that the ecological flow regime implemented in the Rupert River was adequate to maintain anadromous coregonine populations. Impact statementThe establishment of a ecological flow regime has ensured the successful recruitment of anadromous Cisco and Lake Whitefish populations in the Rupert River (northern Quebec, Canada), the flow of which has been partially diverted for hydroelectric purposes. [ABSTRACT FROM AUTHOR]

Reconciling environmental conservation with growing demands for food, water, and energy is a global challenge. Brazil, a major agricultural producer, grapples with deforestation's environmental costs. The Araguaia River basin, vital for Brazil's economic growth, undergoes significant land use changes. Assessing data from 1987 to 2019, we studied annual water surface variations, considering deforestation, agriculture, livestock farming land, and central pivot irrigation, and historical water flow series from 1980 to 2020 from 21 monitoring stations. We observed notable reductions in flooded areas (angular coefficients from 130 a 2,276 ha/year) and water flow the entire basin (b = − 13.84; t = − 4.8; P < 0.001) and its regions (Upper Araguaia: b = − 3.32; t = − 4.5; P < 0.001; Middle Araguaia: b = − 8.70; t = − 4.8; P < 0.001; Lower Araguaia: b = − 45.49, t = − 4.7; P < 0.001) over recent years. Water flow reductions persist year-round, with a marked decrease during low water periods (F3,8 = 8.82; P = 0,006), aligning with heightened water demand for intensive agriculture. Tributaries and the main channel show similar reduction processes (t = 0.16; g.l. = 19; P = 0.873). Ensuring the basin's ecological flow is imperative for the aquatic ecosystem's minimum requirements. [ABSTRACT FROM AUTHOR]

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Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Amid diverse water demands, the conflict between ecological flow adjustments and power generation flow adjustments in hydropower station water resource dispatching, coupled with an increasing diversity of constraints, complicates the issue of water resource optimization and dispatching. How to scientifically develop feedback regulation mechanisms to promote a virtuous ecological cycle, fine tune existing hydropower station scheduling plans, and achieve multi-objective optimization scheduling is the core issue in researching the comprehensive utilization of water resources. This study establishes a reservoir flow regulation model with the objective functions of maximizing power generation and achieving optimal average ecological protection. The model, constrained by water balance, reservoir capacity, unit output, and unit overflow, was optimized and solved using the genetic algorithm-backpropagation neural network (GA-BPNN) approach. This study establishes a reservoir flow regulation model with the GA-BPNN algorithm was applied in multi-objective optimization to identify an optimal solution that maximizes overall system performance while adhering to ecological flow constraints. The results indicate that the optimized plan has performed effectively in hydropower station operations. It not only satisfies ecological flow requirements, but also significantly enhances power generation efficiency. Specifically, power generation increased by 32,680 kw·h, a 23.85 % growth rate. The optimized plan significantly enhances the comprehensive utilization efficiency of water resources. It offers a scientific basis for the rational planning, dispatching and utilization of water resources in hydropower stations and reservoirs.

Water resources variability and availability in a basin affect river flows and sustain river ecosystems. Climate change and human activities disrupt runoff sequences, causing water environmental issues like river channel interruptions. Therefore, determining ecological flow in changing environments is challenging in hydrological research. Based on an analysis of long-term changes in hydrological and meteorological variables and interruption conditions in the semi-arid Liu River Basin (LRB), this study summarizes the controlling factors of river interruption at different temporal and spatial scales and proposes a framework to determine ecological flow under changing environments. Hydrological model and the monthly optimal probability distribution were used to determine the optimal ecological runoff of LRB. The results showed that from 1956 to 2017, precipitation and potential evapotranspiration in the basin showed no significant decreasing trend, but the streamflow significantly decreased, and the downstream interruption worsened, with an average annual interruption duration of 194 days at Xinmin Station from 1988 to 2017. The controlling factors of river interruption are as follows: (1) soil and water conservation measures in the upstream significantly reduce the runoff capacity; (2) the operation mode of the controlling reservoir in the middle reaches changes from "all-year discharge" to "winter storage and spring release" to "combined storage and supply," severing the hydraulic connection between upstream and downstream; and (3) siltation in the downstream river channel coupled with over-extraction of groundwater increases the seepage capacity of the river. The monthly ecological flow of Naodehai Reservoir was determined by considering the monthly seepage losses after reconstructing the natural runoff using the SWAT model and determining the optimal probability distribution function for monthly runoff. The findings are important for downstream LRB ecological restoration and for determining the ecological flow of other river basins in changing environments. [ABSTRACT FROM AUTHOR]

Hydro power has provided significant economic benefits to society due to its cleanliness and convenience. As the number of hydropower stations has increased, many serious ecological issues have also emerged. This study uses Wan'an Reservoir as its research object and investigates single–multi-objective optimal operation and decision-making regarding reservoirs for ecology-oriented operation, to meet ecological water demand and seek the optimal operation schemes for energy generation and ecological benefits. The full-process research is conducted based on the "objective-modeling constraint optimization scheme decision-making" framework. The Mann–Kendall test and ordered clustering method were used to diagnose the hydrological variation in the basin. Based on this, a hierarchical and phased ecological flow process was derived. The objectives were defined according to the flow process, and optimal operation models were constructed. The differential evolution algorithm (DE) and improved non-dominated sorting genetic algorithm-II (NSGA-II) were used to solve the models. A non-fitting curve method was used to determine the approximate inflection point of the Pareto front curve, and the curve was fitted linearly according to the approximate inflection point to obtain the conversion formula between the objectives. Based on the coefficient of variation and Mahalanobis distance, a new multi-attribute decision-making method for reservoir operation, CV-ITOPSIS, was constructed by improving the traditional TOPSIS. The results show that: (1) There is a piecewise linear contradiction between energy generation and ecological objectives, and the contradiction intensifies with an increase in incoming water frequency. (2) Before the approximate inflection point, the head significantly influences the conversion rate from the energy generation to ecology, while the discharge flow is the major influencing factor after the inflection point. The inflection point and the formula for the piecewise straight line can reveal the conversion law between the two objectives. (3) CV-ITOPSIS considers the degree of differentiation of index data and fully considers the correlation between indicators while retaining the good evaluation performance of the traditional method. It recommends the optimal benefit scheme for a multi-objective non-inferior solution set. The research results provide a theoretical foundation and decision support for the optimal ecological operation of the Ganjiang River Basin. [ABSTRACT FROM AUTHOR]

Human activities have significantly altered the hydrological processes of rivers. In recent years, the increased focus on global water resource exploitation and land use changes has heightened the significance of related ecological and environmental issues. To investigate the land use changes in Hulan River Basin between 1980 and 2020, and the corresponding flow under various ecological standards, a quantitative assessment of land use changes in Hulan River Basin was conducted by analyzing the Land Use Dynamic Degree (LUD) index and the land use change matrix. Two types of models, namely natural runoff models and status quo runoff models, were developed to evaluate alterations in basin runoff. Various hydrological techniques were utilized to calculate the ecological water deficit in Hulan River Basin. The results suggest the following: (1) human consumption comprises approximately 40% of surface water resources, with Hulan River Basin exhibiting a moderate consumption level; (2) when determining the minimum ecological flow, the Distribution Flow Method (DFM) method yielded slightly higher outcomes compared to alternative methodologies; both the variable Q90 method and DFM (Q2) method satisfy 10% of the natural river flow, however, in terms of capturing the hydrological pattern, DFM exhibits a slightly lower fitting degree compared to the variable Q90 (monthly average flow with 90% guarantee rate) method; (3) DFM is identified as scientifically reasonable for determining the most suitable ecological flow in comparison to other hydrological methods; (4) despite the widespread water scarcity in Hulan River Basin, the variance between most periods and the ideal ecological flow remains minimal, indicating that severe water shortages are uncommon. [ABSTRACT FROM AUTHOR]

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Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In Brazil, 65% of the electric power production comes from hydroelectric power plants (HPPs). In some cases, these power plants divert the course of rivers, resulting in regions impacted by the absence of water, which are known as reduced fow sections (RFS). These sections are regulated by legislation and aim to maintain the minimum fow necessary to preserve the fauna, flora, fish, and human consumption in the region. Depending on the time of year, this minimum flow, also known as ecological flow (residual flow), can reach significant values, resulting in the interruption of power generation in these HPPs. This article presents a study case of two hydroelectric power plants located in different Brazilian states. The objective of this study is to explore the feasibility of implementing auxiliary generator groups that can operate uninterruptedly at different drop heights while ensuring the preservation of residual flow during low flow periods or taking advantage of the overflow flow by spillways during high flow periods. This auxiliary system would use the same set of structures and transmission systems as the main power plant, minimizing environmental impacts and implementation costs, allowing this solution to be implemented in HPPs that face this type of problem in Brazil. The results obtained indicate that HPPs with larger reservoirs have a greater ability to maintain residual flows with minimal generation loss and that run-of-the-river power plants are the most impacted by the maintenance of residual flow.

The fact that rural hydropower stations are scattered in sites and discharge facilities differ widely in their forms causes the high costs of ecological flow discharge monitoring in China. Meanwhile, the irregularity of river sections and the randomness of hydrological situations also increase the difficulty of flow monitoring, impeding the extensive application of regular monitoring equipments. Under such circumstances, non-contact video recognition is an effective alternative. Based on the data extracted from a large number of ecological flow discharge videos, the authors develop a video recognition intelligent algorithm, which can be used to identify whether the ecological flow has been discharge or not. By combining a main algorithm and a sub-model, this system ensures not only the universality and ease of use of the identification, but also the accuracy of the identification results. The authors also develop a water conservancy video AI general component system, which integrates the video recognition intelligent system and the identification business process, and has been put into use in 499 rural hydropower stations through a period of five months. The effectiveness and promotion value of this system is testified by the statistics of all recognition results: after ruling out the cases where the videos or images are blurred, the average recognition accuracy under normal conditions is 97.8%. [ABSTRACT FROM AUTHOR]

In Brazil, 65% of the electric power production comes from hydroelectric power plants (HPPs). In some cases, these power plants divert the course of rivers, resulting in regions impacted by the absence of water, which are known as reduced flow sections (RFS). These sections are regulated by legislation and aim to maintain the minimum flow necessary to preserve the fauna, flora, fish, and human consumption in the region. Depending on the time of year, this minimum flow, also known as ecological flow (residual flow), can reach significant values, resulting in the interruption of power generation in these HPPs. This article presents a study case of two hydroelectric power plants located in different Brazilian states. The objective of this study is to explore the feasibility of implementing auxiliary generator groups that can operate uninterruptedly at different drop heights while ensuring the preservation of residual flow during low flow periods or taking advantage of the overflow flow by spillways during high flow periods. This auxiliary system would use the same set of structures and transmission systems as the main power plant, minimizing environmental impacts and implementation costs, allowing this solution to be implemented in HPPs that face this type of problem in Brazil. The results obtained indicate that HPPs with larger reservoirs have a greater ability to maintain residual flows with minimal generation loss and that run-of-the-river power plants are the most impacted by the maintenance of residual flow. [ABSTRACT FROM AUTHOR]

Climate is probably the most important factor affecting river discharge and flow dynamics. Low flows in rivers during the warm period cause stress to aquatic ecosystems and pose a challenge to sustainable water management. Previous research has shown that the average minimum discharge of the 30 driest continuous days, known as Q30, is a suitable measure for ecological flow estimation in Lithuania. This study aims to examine whether large-scale atmospheric processes, so-called teleconnections, can have an impact on Q30 during the warm period. Hydrological data for 1961–2020 from 25 water gauging stations were used to search for hydrological response signals with five selected climate indices (NAO, SCA, POL, EA/WR, and EA). Pearson correlation and Wilcoxon–Mann–Whitney test approaches were applied. The results suggested that the EA/WR and NAO had the strongest influence on Q30 in the studied region during the warm period. The positive phases of the indices tended to cause a greater decrease in Q30 values due to the prevailing easterly edge of the anticyclonic circulation over the studied region determined by the EA/WR and NAO indices, while the negative phases of the mentioned indices caused an increase and greater dispersion of Q30. [ABSTRACT FROM AUTHOR]

Between the preservation of aquatic ecosystems and the demand for water collection from rivers, complex problems arise for water resource management. To enable the continuity of the ecological functions offered by the water, a flow that sustains the aquatic ecosystem has to be maintained. This study aims to compare different methods of ecological flow calculation and their applicability in an urbanised watershed, discussing the resulting environmental and social implications in the context of a developing country. The 7Q10, Northern Great Plains Resource Program, and Ecological Hydraulic Radius approaches were used. The 7Q10 was chosen because it is a method widely used in Brazil and the others for their ecological considerations and the availability of data for the study area. The results showed that the daily flow crossing the rivers of the urban watershed is not enough to promote the maintenance of the aquatic ecosystem. The 7Q10 method presented an admissible ecological flow (0.38 m3/s) due to the absence of ecological parameters in the modelling and this differed from the other approaches. We highlight the need to develop an ecologically sustainable water management program for the recovery and revitalisation of the waterways in the basin. [ABSTRACT FROM AUTHOR]

Scientific ecological hydrological indicators provide constraints that contribute to the healthy operation and restoration of river ecosystems. Daily flow data from three Jing River outlets (SongZiKou (SZK), TaiPingKou (TPK), and OuChiKou (OCK)) spanning 1955–2019 were used. We employed innovative methods, such as IHA–RVA and annual distribution, to establish ecological flow thresholds. Surplus and deficit indicators were used to analyze annual and seasonal runoff dynamics. The PCA/RVA method identified relevant hydrological indicators and assessed hydrological changes influenced by the Three Gorges Reservoir (TGR). Key findings include suitable ecological flow thresholds for the flood season (SZK/TPK/OCK – 218.6/94.5, 51.7/96.0, and 60.9–4,494.5 m3/s, respectively). The TGR impacted the flow duration curve, causing deficits during the flood season (up to 0.99, OCK) and surpluses in non-flood seasons (up to 5.04, OCK). The study assessed the Jing River watershed's response to hydrological changes, notably due to the reservoir's water storage and flow interruption during the dry season, revealing declining low pulse count (SDG) and duration (MTS) and increasing high pulse duration (GJP). This research employs innovative methods and hydrological indicators, enhancing understanding of Jing River watershed ecological hydrology, and offering essential data for water resource management and ecosystem health. HIGHLIGHTS The IHA–RVA method was used to study the biological flow thresholds and changes of three outlets of Jingjiang River in the middle of Yangtze River based on 60 years of daily flow data.; This study applied PCA and RDA to filter IHA for ERHIs, addressed redundancy issues, and investigated the ERHI's variation during dry period breaks and the Three Gorges Reservoir.;

Ecological flow is a restrictive condition set for human water consumption in water resources management to protect river ecosystems. However, uncertainties in hydrological conditions, changes in regulatory capacity, and temporal-spatial differences bring difficulties to the implementation and supervision of ecological flows. By analyzing the relevant concept and connotation of ecological flow, it is concluded that the ecological flow regimes suitable for practical application should be a dynamic interval rather than a fixed value. Therefore, an improved ecological flow calculation method was proposed, which is to increase the feasible lifting volume for different ecological service objects based on the determined ecological baseflow. Taking two cross-sections of the Weihe River as an example, the ecological flow was calculated by comprehensively considering the factors of inflow, fish survival, landscape, and agricultural irrigation. The result shows the lifting volume occurred in the high flow season (April–June), and the maximum ecological flow of LJC and WJB cross-sections was 20.2 and 16.0 m3/s, respectively. Moreover, it is a generalized approach that can be extended to a more complicated river system, and the calculation results have reliability and adaptability in integrated water regulation. HIGHLIGHTS The variable interval analysis method has a positive contribution to the results' rationality.; Intervals are more adaptive than a value or a set of values in ecological flow calculations.; The proposed strategies can bring the flow regimes more in line with practical requirements.;

This study analyzed 61 years of hydrological data from the Minhe and Xiangtang Hydrological Stations (1956–2016) to examine hydrological changes and ecological flow assurance rates in the Huangshui River Basin, China. Using the Mann–Kendall trend test, IHA/RVA method, and ecological flow calculation methods, the study revealed the following results: (1) After 1994, increased human activity in the Datong River led to a measured runoff decrease compared to natural runoff. Although human activities in the Huangshui River’s main stream were present before 1972, after 1972, these activities intensified, resulting in a more pronounced decrease in the measured runoff. (2) Ecological flow analysis indicated that the main stream of the Huangshui River and the Datong River have ecological flow assurance rates of 100% for all but a few months, where the rates are 98%. The water volume is sufficiently abundant to meet ecological water demands.

In order to safeguard the health of river ecosystems and maintain ecological balance, it is essential to rationally allocate water resources. This study utilized continuous runoff data from 1967 to 2020 at the Zhouqu Hydrological Station on the Bailong River. Five hydrological methods, tailored to the hydrological characteristics of the Zhouqu hydrological cross-section, were employed. These methods included the improved dynamic calculation method, the NGPRP method, the improved monthly frequency computation method, the improved RVA method, and the Tennant method. Ecological flow calculations were conducted to determine the ecological flow, with analysis carried out through the degree of satisfaction, economic benefits, and the nonlinear fitting of the GCAS model. We established an ecological flow threshold and early warning program for this specific hydrological cross-section. Ecological flow values calculated using different methods for each month of the year were compared. The improved RVA method and Tennant method resulted in small values ranging from 4.05 to 36.40 m3/s and 7.65 to 22.94 m3/s, respectively, with high satisfaction levels and economic benefits, but not conducive to ecologically sound development. In contrast, the dynamic calculation method, NGPRP method, and improved monthly frequency calculation method yielded larger ecological flow values in the ranges of 21.79–97.02 m3/s, 23.90–137.00 m3/s, and 28.50–126.00 m3/s, respectively, with poor fulfillment and economic benefits. Ecological flow thresholds were determined using the GCAS model, with values ranging from 16.72 to 114.58 m3/s during the abundant water period and from 5.03 to 63.63 m3/s during the dry water period. A three-level ecological warning system was proposed based on these thresholds, with the orange warning level indicating optimal sustainable development capacity for the Zhouqu Hydrological Station. This study provides valuable insights into the scientific management of water resources in the Bailong River Basin to ensure ecological security and promote sustainable development.

Copyright of Pearl River is the property of Pearl River Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Climate change is producing large impacts on rivers, amplifying hydrological extremes. Prolonged drought periods result in dramatic stress for river biota and associated processes due to low discharge, reducing the interactions between rivers and their lateral environments or leading to hydrological intermittency. New quantitative methods are needed, to correlate discharge with the available riverine habitats. In this work we have mapped the wet surface and paths of two stretches of the Taro and Trebbia Apennine rivers, analyzing satellite images from periods with contrasting discharge. The considered stretches are critical due to different human pressures (large water withdrawals for agriculture and industrial use) and are particularly vulnerable to further, climate‐driven discharge reductions. The produced images offer multiple possibilities to extract qualitative and quantitative information at the whole stretch scales, including habitat reduction along with decreasing discharge, threshold discharge limiting lateral interactions, or the evaluation of longitudinal river continuity. We discuss the limitation and the potentialities of the method and the maps produced in terms of possible application in the field of river geomorphology, ecology, the definition of ecological river flow, risk assessment, and river management. [ABSTRACT FROM AUTHOR]

Climate change and human activities have greatly altered the ecological flow of rivers, and the conflict between human water use and natural water demand is becoming more and more prominent. Using two ecological flow indicators (ecodeficit and ecosurplus), this study focuses on assessing the characteristics of ecological flow changes at multiple time scales and introduces the Long Short-Term Memory model to construct a meteorological streamflow model for the Xiangjiang River (XJR) basin, using a separation framework to quantify the effects of human disturbance and climate change on ecological flow at multiple time scales. In addition, the fluvial biodiversity Shannon Index (SI) was used to assess the response processes of riverine ecosystems under changing conditions. The results show that the increase of XJR flow is larger (11%) after 1991, the increase in precipitation and potential evapotranspiration in the basin is 5.60%, and the decrease is 3.09%, respectively, and there are obvious cycles of all three on annual and seasonal scales. The annual ecosurplus increased, and the annual ecodeficit decreased after the hydrological variation; on the seasonal scale, the ecodeficit decreased significantly in summer and autumn, and the ecosurplus increased substantially in winter. Climatic factors were the main drivers of the increased frequency and magnitude of annual, summer, and fall high flows (91%, 94%, and 65% contributions, respectively), while urbanization expansion and reservoir diversions drove the increase in spring ecodeficit. Changes in river flow maintained the ecosurplus at a low level after 2002, further causing a decrease in river biodiversity, and the annual and summer ecosurplus were highly correlated with SI indicators (0.824 and 0.711, respectively). Our study contributes to the development of effective ecological flow regulation policies for the XJR basin. [ABSTRACT FROM AUTHOR]

The reasonable determination of ecological flow is o£ great significance for the efforts to promote the transformation of water ecological environmental protection from pollution management to synergistic management of water resources, water ecology and water environment, and to promote them in an integrated manner. This paper analyzed and calculated the ecological flow process of the Bangsha River diversion power station using the minimum ecological flow method, the annual spreading method, the improved annual spreading method, the NGPRP method, and the month-by-month frequency method, and evaluated the reasonableness of the process and results of the ecological flow calculations by using the fuzzy evaluation model established. The study showed that the minimum ecological flow rate determined by improving the coupling of the spreading method and the NGPRP method was the best, and the suitable ecological flow rate determined by the month-by-month frequency method was the best; the minimum ecological flow rate of the Bangsha River diversion power station was at 0.43 -4. 21 m3/s, and the suitable ecological flow rate was at 0. 56 -- 4. 94 m3/s, and the trend of its change showed the trend of first increasing and then decreasing, and the trend of change from January to July showed the trend of first increasing and then decreasing. Its trend of change showed an increasing and then decreasing trend, from January to July showed a gradually increasing trend, from August to December showed a gradually decreasing trend. It aimed to provide a theoretical basis for the reasonable determination of the ecological flow of the river hydropower station. [ABSTRACT FROM AUTHOR]

Ecological flow (E-flow) determination is an essential component of stream management and the preservation of aquatic ecosystems within a watershed. E-flow should be determined while considering the overall status of the watershed, including the hydrological cycle, hydraulic facility operation, and stream ecology. The purpose of this study is to determine E-flow by considering watershed status through coupled modeling with SWAT and PHABSIM. SWAT was calibrated to ensure reliability when coupling the two models, using observed data that included streamflow and dam inflows. The calibration result of SWAT showed that the averages of R2, NSE, and RMSE were 0.62, 0.57, and 1.68 mm/day, respectively, showing satisfactory results. Flow duration analysis using the SWAT results was performed to apply to discharge boundary conditions for PHABSIM. The averages of Q185 (mid-range flows) and Q275 (dry conditions) were suitable to simulate fish habitat. The habitat suitability index derived through a fish survey was applied to PHABSIM to estimate E-flow. E-flow was estimated at 20.0 m3/s using the coupled model and compared with the notified instream flow by the Ministry of Environment. The results demonstrate a high level of applicability for the coupled modeling approach between the watershed and physical habitat simulation models. Our attempt at coupled modeling can be utilized to determine E-flow considering the watershed status. [ABSTRACT FROM AUTHOR]

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Although regional and seasonal water scarcity occurs frequently in China, and the contradiction among domestic, production and ecological water is prominent in some watersheds, the Chinese government still attaches great importance to the determination and implementation of ecological flow of rivers or lakes. Practitioners have been seeking methods to determine the ecological flow of rivers or lakes and how to ensure its implementation. Taking the Dingnan River watershed as a case, drawing on the experience of ‘Hedging rule’, the ‘Determination-Assessment-Reduction’ for the ecological flow nexus approach (the D-A-R approach) is introduced, which includes the determination of the annual ecological flow process through the river section, the assessment of water scarcity degree of the watershed and various water reduction strategies, respectively, and respond to the three scenarios of ‘general type, saving type and constrained type’ during the gap period. The results show that it is possible to use the D-A-R approach to proactively and dynamically adjust the ecological flow according to the probability estimate of that amount of water inflow per month, which the adjusted ecological flow threshold can better adapt to water scarcity at different levels and alleviate the contradiction among domestic, production and ecological water in the watershed during the dry period. HIGHLIGHTS Drawing on the experience of the ‘Hedging rule’, the ‘synchronous reduction strategy’ about the demand for domestic, production and ecological water is proposed.; The D-A-R approach is an ecological flow determination approach combined with assessment and reduction.; The new approach is proposed to strengthen water allocation to water users with potential future water scarcity to degrade the probability of suffering more serious water scarcity events in the later stage.;

Hydro power has provided significant economic benefits to society due to its cleanliness and convenience. As the number of hydropower stations has increased, many serious ecological issues have also emerged. This study uses Wan’an Reservoir as its research object and investigates single–multi-objective optimal operation and decision-making regarding reservoirs for ecology-oriented operation, to meet ecological water demand and seek the optimal operation schemes for energy generation and ecological benefits. The full-process research is conducted based on the “objective-modeling constraint optimization scheme decision-making” framework. The Mann–Kendall test and ordered clustering method were used to diagnose the hydrological variation in the basin. Based on this, a hierarchical and phased ecological flow process was derived. The objectives were defined according to the flow process, and optimal operation models were constructed. The differential evolution algorithm (DE) and improved non-dominated sorting genetic algorithm-II (NSGA-II) were used to solve the models. A non-fitting curve method was used to determine the approximate inflection point of the Pareto front curve, and the curve was fitted linearly according to the approximate inflection point to obtain the conversion formula between the objectives. Based on the coefficient of variation and Mahalanobis distance, a new multi-attribute decision-making method for reservoir operation, CV-ITOPSIS, was constructed by improving the traditional TOPSIS. The results show that: (1) There is a piecewise linear contradiction between energy generation and ecological objectives, and the contradiction intensifies with an increase in incoming water frequency. (2) Before the approximate inflection point, the head significantly influences the conversion rate from the energy generation to ecology, while the discharge flow is the major influencing factor after the inflection point. The inflection point and the formula for the piecewise straight line can reveal the conversion law between the two objectives. (3) CV-ITOPSIS considers the degree of differentiation of index data and fully considers the correlation between indicators while retaining the good evaluation performance of the traditional method. It recommends the optimal benefit scheme for a multi-objective non-inferior solution set. The research results provide a theoretical foundation and decision support for the optimal ecological operation of the Ganjiang River Basin.

With rapid economic and social development, human activities, such as the construction of reservoirs, have satisfied many needs. However, these activities have also caused changes in the hydrological ecosystem of the basin, impacting river biodiversity. The establishment of the Shanxi Reservoir within the Feiyun River Basin has inevitably altered the hydrological system, which was previously shaped primarily by precipitation. This study comprehensively evaluates the impact of Shanxi Reservoir on the hydrological alteration of the basin. Two ecological flow indicators, ecosurplus and ecodeficit, were used based on flow duration curves, along with the Shannon Index of river biodiversity (SI) and several hydrological indicators: the Indicator of Hydrological Alteration (IHA), the Degree of Integrated Hydrological Alteration (D0), and the Dundee Hydrological Regime Alteration Method (DHRAM). The results of the study show that: (1) the previously observed correlation between ecological flow and precipitation was disrupted following the construction of the reservoir. As a result, there was a notable ecological deficit in the spring season, with a maximum of 0.43, and a considerable increase in ecological surplus during winter, reaching a maximum of 4.80. (2) The flow regime of the river has undergone significant changes, resulting in a combined hydrological variability of 66. 44% and an ecological hazard level of 4. This indicates a high risk to the river’s ecological environment. (3) The total seasonal ecological surplus has increased and remained consistently high, which has contributed to a decline in the SI of river biodiversity, the river's biology has degraded over time (4) The use of ecological flow indicators is closely tied to IHA32 indicators. Combining ecological flow indicators with ERHIs has shown to be a successful approach for assessing ecohydrological regimes. These findings have significant implications for future studies in similar cases and offer valuable guidance for managing water resources.

Hydropower development brings benefits in terms of power generation and flood control, but it also has inevitable ecological impacts. These impacts must be considered and addressed in order to ensure sustainable development and minimize harm to the environment. This study utilized the MIKE 11 HD modeling system to construct a hydrological and hydrodynamic model of the Jianhe River basin. The model incorporates the flow demand of ecologically sensitive targets for scheduling purposes and was calibrated and validated using hydrological data from 2014 to 2022. The hydrodynamic model was then applied to analyze the evolution characteristics of the water level in the main stream of the Jianhe River, identify key areas and periods for hydropower station operation, and calculate the minimum ecological water requirement using verification and estimation methods. Based on these findings, an ecological dispatching scheme for the cascade hydropower stations in the Jianhe River basin was developed. The results demonstrate satisfactory performance of the constructed NAM model for rainfall runoff and the 1D hydrodynamic MIKE 11 HD model for the Jianhe River basin. The deterministic coefficients exceed 0.8, and the relative errors in the total water volume are below 5.5%. The critical time and space interval for hydropower station operation in the main stream of the Jianhe River is identified as December to February of the following year, with the highest risk of flow interruption occurring in January, primarily concentrated between the Duoluo II and Huahai hydropower stations. If the appropriate dispatching scheme is not implemented in the areas prone to flow interruption during critical periods, it will have a negative impact on the ecological environment. These findings provide a scientific basis and decision support for developing multi-objective ecological flow guarantee schemes for rivers. [ABSTRACT FROM AUTHOR]

China's Ecological Conservation Redline (ECR) program ensures the coordination and sustainability of natural and economic development while maintaining regional ecological security. Current research focuses on the ecosystem services within ECR areas but ignores cross-boundary ecological flow and the interactions between the internal and external ecological effects of ECR areas. In addition, the ecological background has spatial continuity that is not limited by boundaries, and the radiation effect areas extending beyond ECR areas have not been quantified. In this study, the Beijing ECR areas and ecological security network were integrated in order to connect the ecological process and landscape pattern to the ECR through the circulation path of ecological corridors, and cross-boundary effects between patches were examined. The field spread model was used to quantify the radiation influence range of ECR areas. Additionally, 972.46 km of ecological corridors were identified in Beijing, and abundant corridors effectively linked the ECR areas and maintained the material cycle. In the surrounding areas, ecological corridors were spread radially, with a total length of 941.85 km, promoting cross-boundary ecological flow between the ECR and surrounding source areas. This study used 25 ecological nodes to constitute the cross-boundary ecological security network system. The total radiation area based on the ECR source was 9572.16 km2. These results provide support for the radiation effect of ECR and cross-boundary ecological flows and suggest a useful model for sustainable ecological development and cross-boundary management. [ABSTRACT FROM AUTHOR]

To quantitatively study the hydrodynamic changes in different river morphologies and clarify the impact of morphological changes on river ecosystems, this study examined a section of the Nansha River near Laoniuwan in the Haidian District, Beijing, and characterized different river morphologies by river sinuosity. The River 2D model was used for simulation and analysis, and the depth and velocity diversity indices were introduced to quantify the distribution of depth and velocity under different sinuosities. Cyprinus carpio was selected as the target fish in this study, and its suitability curve was determined using literature and field surveys. Combined with the simulation results, a weighted usable area curve was established to identify its inflection point and maximum value and determine the ecological flow in the river under different sinuosities, that is, to clarify the relationship between sinuosity and ecological flow. The results showed that the lower the sinuosity, the worse the depth and velocity diversity, but a greater sinuosity did not lead to better depth and velocity diversity. The depth and velocity diversity of a sinuosity of 1.5 were better than those of 1.89 in general, except for low flow conditions (Q = 5 m3/s). For rivers with water use restricted by nature and society and where ecological needs exist, ecological engineering that appropriately changes the planform of rivers can be considered to increase the diversity of river/channel geometry and provide a basis for the ecological restoration of rivers. [ABSTRACT FROM AUTHOR]

This study develops a convolutional recurrent deep learning model to accurately predict fine‐resolution spatiotemporal changes in grass coverage in arid regions. Applying the model to the Gobi Desert reveals that ecological flow regulation contributes to 61.8% of the total increase in grass cover (130.6 km2) in the study area (40,423 km2) over 2005–2015, nearly triple the contribution of local climate change (+23.0%). The transboundary hydrological impact (+32.4%) and interactions between drivers (−17.2%) are also significant. In an intermediate future climate change scenario, we found no statistically significant trend for the total grass‐covered area due to the counteracting effects among different drivers. The study findings suggest that timely, adaptive and spatially heterogeneous ecological flow management is crucial for addressing grassland degradation in arid regions. This study provides a promising approach to land surface modeling under climate change and human disturbance and expands the existing understanding of the global greening process. Plain Language Summary: The Earth's recent greening (i.e., vegetation increase) has boosted the terrestrial carbon sink, intensified the hydrologic cycle, and contributed to mitigating global warming. CO2 fertilization has been identified as the primary cause at the global scale, while climate change, land use changes, and nitrogen deposition also contribute. However, there are still many gaps in our understanding of how grasslands in arid areas are being affected. Studies in Central Asia identified precipitation as the dominant factor affecting grassland change and grazing as the main influence from humans. Based on satellite data, we employ a novel deep learning (DL) approach to emulate spatiotemporal changes in grass coverage at a 1‐km resolution over an area of 40,423 km2 in the Gobi Desert in northwestern China. Our study identified previously overlooked mechanisms contributing to the increase in grass coverage, including ecological flow management and transboundary hydrological impact. Ecological flow management was found to be responsible for almost three times the increase in grass coverage over 2005–2015 than that of local climate changes. Our findings suggest that timely, adaptive, and spatially targeted ecological flow management is urgently needed to prevent further grassland degradation in arid regions, and DL‐based artificial intelligence can offer valuable management suggestions. Key Points: Deep learning (DL) precisely emulates spatiotemporal changes in grass coverage at a 1‐km resolution over an area of 40,423 km2DL interprets ecological flow regulation (EFR) as the leading cause of grassland greening in the Gobi DesertTimely, adaptive and spatially heterogeneous ecological flow management is desired to prevent grassland degradation in arid regions [ABSTRACT FROM AUTHOR]

Water resources and aquatic ecosystems are facing significant threats due to unsustainable water management practices. To address this challenge in Romania, a sustainable approach to water management is necessary, re-thinking ecological flow. This article proposes a re-thinking of the current approach to ecological flow in Romania by advocating for a more holistic and integrated approach considering environmental factors. The objective of the article was to present a methodology for the establishment of ecological flow that took into account the natural variability of flows. Four ecological flow values related to flood, high-water, medium-water, and low-water hydrological regimes were defined. To establish them, the duration curve of average daily flows was used in conjunction with hydromorphological and biological indicators. The proposed methodology was applied and compared to the existing methodology for the Uz river developed with hydropower use. The methodology represents a transition from the anthropocentric perspective to the sustainability perspective. The proposed methodology is easy to apply, with rigorously defined hydrological, hydraulic, and biological criteria. This research was conducted within the Hydrotechnical Faculty to refine the Romanian legislation regarding the improvement of the ecological status of all rivers. [ABSTRACT FROM AUTHOR]

The main objective of most hydropower systems is to pursue the efficient use of water resources and maximize economic benefits. At the same time the protection of ecological environment should not be neglected. In this study, a coordination model of power generation and ecological flow for the operation of cascade hydropower system was first established using a multi-objective optimization method. Multi-objective genetic algorithms (MOGAs) are widely used to solve such multi-objective optimization problems because of their excellent performance in terms of convergence speed, diversity of solution set space and optimality seeking ability. However, the adaptability of MOGAs to a particular optimized operation problem sometimes varies widely. It is of great significance to investigate the adaptability of different algorithms for a new optimized operation problem and to recommend a more suitable solution algorithm. Three MOGAs namely NSGA-II, NSGA-III and RVEA are selected to solve the proposed optimized operation model. Numerical experiments were conducted to evaluate the performance of the algorithms using real-world data from a cascade hydropower system located in the lower Yalong River. The results show that the Pareto fronts corresponding to NSGA-II and NSGA-III significantly dominate the Pareto fronts corresponding to the RVEA. The Pareto fronts corresponding to the NSGA-III algorithm are slightly better than those of NSGA-II. In terms of the four performance metrics, NSGA-III has certain advantages over NSGA-II and RVEA. NSGA-III is recommended as the solution algorithm for the established coordination model of power generation and ecological flow. [ABSTRACT FROM AUTHOR]

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dam control changes the hydraulic environment and hydrological rhythm of rivers; to explore the causes of fish habitat loss and influence of river regulation in such rivers, the downstream curving reaches of Shaying River were cut off. Grass, silver, and bighead carp were selected as the research targets, and the impact of waterway regulation and the effect of gravel mounds on the target fish habitat were studied using numerical simulation. The results show that the original channel's hydraulic environment is similar to the artificial channel, and the target fish spawning habitat is limited, which is an important reason for the shortage of fish resources in the research area. The reconstructed channel can meet the river's navigation demands and improve the channel's flood discharge capacity. The habitat method was used to estimate the minimum and appropriate ecological flows of the target fish at each growth stage in the original and reconstructed rivers. Under the appropriate ecological flow, the weighted usable area (WUA) of juvenile, migratory, and spawning habitats of the target fish in the reconstructed river increased by 168, 24, and 580%, respectively, compared to the original channel, while the WUA of adult fish that preferred a slow-water environment decreased by 62%, effectively improving the target fish's spawning environment. HIGHLIGHTS The habitat distribution of the four major Chinese carps in the whole life cycle was screened and analyzed.; The study shows the complete research process from waterway regulation to biological habitat restoration to ecological flow calculation.; A biological habitat restoration scheme with gravel mounds was adopted, and the navigation and flood discharge capacity of the waterway was not affected.;

Dam operation is regarded as an effective way to increase water, food, and energy security for society. However, with the increasing water demand and frequent extreme droughts, numerous rivers worldwide go through periods of water scarcity and water ecosystem deterioration to varying degrees. Balancing the water supply and ecological flow of the dam-regulated river network is essential in the context of river restoration. In this study, we proposed a hydrodynamic and water quality model of a dam-regulated river network balancing water supply and ecological flow using the Environmental Fluid Dynamics Code (EFDC). A section of Jinjiang watershed located in the southwestern of China was chosen as the study area. Firstly, the model was calibrated and validated. By comparing the simulated values with the measured values, the statistical analysis results showed that the relative root mean-squared error (RRMSE) values of water level, COD and NH3-N were 5.5–8.1%, 23.6% and 28.4%, respectively, indicating an adequate degree of agreement between simulation and observation. Based on the established model, dam operation schemes under a dry hydrologic scenario and emergency contamination scenario were formulated to ensure the requirement of ecological water flow and water quality simultaneously. For the dry hydrologic scenario, the ecological water requirement could be satisfied through the dam operation. However, in an emergency contamination scenario, regional water quality requirements cannot be met through dam operation. The dam operation only plays a role in controlling the scope of pollution. This study is expected to provide scientific support for dam-regulated river network management and downstream river ecosystem protection. [ABSTRACT FROM AUTHOR]

As the impact of human activities on the natural environment, the natural hydrological regime changes accordingly. A variety of hydrohydraulic methods were used to comprehensively analyze the ecological flow in the Feiyun River Basin for the first time, which is of great significance to maintain the local water ecological health. Based on the 65 years measured runoff data of Feiyun River and the cross sections, the ecological flow of Feiyun River was calculated by six methods: wetted periphery method, annual spread method, 7Q10 method, minimum average monthly flux method, texas method and aquatic base flow method, and the results was verified by using the flow standard setting table of tennant method. Finally, the results of the wetted periphery method, minimum average monthly flux method and the 7Q10 method were selected as the monthly ecological flow value of the main stream of Feiyun River. The flood season of Feiyun River was from April to September, and the required ecological flow value was the maximum in August and September were 38. 74 m 3 / s and 36. 56 m 3 / s. By comparing with the measured monthly average flow, it is found that the ecological flow of Feiyun River in February and August is not satisfied easily, and the proportion of substandard flow is 18. 46% and 16. 92% . Paper clarifies the appropriate ecological flow processes in the Feiyun River Basin, providing a scientific basis for optimal water resource allocation and river habitat improvement in the basin; at the same time, the integrated use of both hydraulics and hydrology provides a new idea to improve the reliability of ecological flow calculation results. [ABSTRACT FROM AUTHOR]

The concepts and calculation of basic, suitable, and fine ecological flow are put forward, and an integrated multi-method to calculate the ecological flow in rivers under multi-objectives is explored. Based on this, a refined calculation theory and method of a multi-objective ecological flow division based on time and space is proposed. That is, three commonly used methods, namely, the hydrology method, the hydraulics method, and the habitat method, are selected to finely calculate the ecological flow demand at different periods, in different sections, and under different ecological objectives. This approach breaks through the traditional ecological water demand calculation method based on hydrology and develops a river ecological flow calculation method based on water environmental protection objectives. A refined calculation method of ecological flow division based on time and space is developed to ensure that the ecological-hydrological process in rivers and lakes meets the ecological flow demand in different periods, different reaches, and different ecological objectives. Taking eight rivers entering Baiyangdian Lake as an example, the ecological flow demand in different river sections under different ecological objectives at different times is calculated to ensure the ecological flow process. The results show that the range of basic ecological flow demand range is 0.07–3.87 m3/s, the range of suitable ecological flow demand is 0.51~10.74 m3/s, and the range of fine ecological flow demand is 0.71~20.29 m3/s. In terms of spatial distribution, Ping River has the lowest demand for ecological flow, and the Zhulong River has the largest. In terms of the interannual ecological demand, those of the Baigou River, Fu River, Xiaoyi River, and Zhulong River are larger. In the demand process across the year, the demand is the largest from July to September, while the demand is the smallest from March to May. Similarly, most rivers face such problems as a sharp decline in runoff, drying up of the river, and an urgent need to restore ecology in northern China. This study also has insights and reference significance for other regions. [ABSTRACT FROM AUTHOR]

Large reservoirs and dams can fundamentally alter downstream flow and thermal regimes by resetting the flow and water temperature release boundary conditions, resulting in significant impacts on fish habitat suitability. Therefore, it is critically important to understand how the volume and temperature of dam releases to influence downstream hydraulic and temperature dynamics and predict the ecological responses of fish habitat suitability to these changes. In this study, a physically based coupled model framework was developed to identify the temporal and spatial variations of hydraulic and water temperature regimes and the spawning habitat suitability of four major Chinese carps (FMCC) in the middle reach of the Yangtze River below Three Gorges Reservoir (TGR) responded to different upstream boundary conditions established by dam operation. The results showed that the dam discharge volume from TGR mainly affected the downstream hydraulic regime, while dam discharge temperature would have most impact on downstream water temperature. The spawning habitat suitability of FMCC obviously decreased due to TGR operation, and the declined water temperature suitability and the delayed and narrowed window of suitable water temperature were the main influencing factors. For the purpose of maximizing the spawning habitat suitability of FMCC in the downstream reaches below TGR, dam discharge volume ranged from 10,000 to 22,500 m3/s, and dam discharge temperature varied from 22 to 23.5°C would be recommended as the outflow conditions in the ecological operation of TGR. [ABSTRACT FROM AUTHOR]