Cascade Reservoirs Research Articles

Variations in Sedimentation Rate and Corresponding Adjustments of Longitudinal Gradient in the Cascade Reservoirs of the Lower Jinsha River

The Xiangjiaba and Xiluodu reservoirs, as important components of the large cascade reservoirs in the lower Jinsha River, and the interactive changes in sediment trapping amounts, the differences in sedimentation dynamics, and the potential mutual influence mechanisms among them are scientific issues worthy of attention. Based on the multiple observed data of thalweg elevation before and after the completion of the dam construction, this study calculated the average sedimentation rates of all 20 km segments of the above-mentioned reservoirs in different periods. Meanwhile, the local mean gradients between adjacent segments and the regional mean gradients from the segments to the dam in the corresponding periods were calculated. The results show that the maximum and average sedimentation rates of the Xiangjiaba Reservoir, which was built earliest and is located downstream, were as high as 19.62 m yr−1 and 8.88 m yr−1, respectively, in the first half year after the dam closure. After the completion of the Xiluodu Reservoir, an adjacent cascade reservoir upstream, the average sedimentation rate of the Xiangjiaba Reservoir in the following seven years dropped to 0.67 m yr−1. The maximum and average sedimentation rates of the Xiluodu Reservoir were 9.07 m yr−1 and 4.15 m yr−1, respectively, within one year after the dam closure, and its average sedimentation rate in the following six years was 2.51 m yr−1. The spatial variations of sedimentation rates in these two reservoirs follow different changing patterns. There is an obvious correlation between the change in mean gradient and the change in sedimentation rate. The sequence of dam construction, the relative positions of the reservoirs, the differences in sediment trapping amounts, and operation modes are the key factors controlling the changes in sedimentation rate and gradient in the reservoir area. This study reveals the interactive changes in sedimentation rates among cascade reservoirs and the response mechanism of river channel morphology, and has a guiding role for the formulation of effective measures for the sustainable utilization of cascade reservoirs.

Cascade reservoirs affect mercury concentrations in fish from Teles Pires river, Brazilian Amazon.

Hydroelectric reservoirs favor mercury contamination in biota, but the contamination in cascade reservoirs is not yet clear. We investigated total mercury (THg) contamination in fish in four cascade reservoirs in the Brazilian Amazon between August 2022 and April 2023. Overall, downstream predatory fish showed higher mercury concentrations than those upstream. Mercury concentrations in predatory fish collected upstream increased in the reservoirs along the river. Downstream, these concentrations were consistently high, with no variation between reservoirs. Non-predatory fish did not exhibit a clear spatial trend in mercury concentrations. Considering that the synergistic effect of cascade reservoirs was evident in predatory fish, and that the species Serrasalmus rhombeus is widely distributed and important for regional fishing, we suggest it as a target species for future studies on thi issue in the region.

Modelling reactive transport of metals in Wujiang cascade reservoirs under coal-fired, hydro power generation and fishing ban scenarios

Modelling reactive transport of metals in Wujiang cascade reservoirs under coal-fired, hydro power generation and fishing ban scenarios

Water temperature's cumulative effect induced by the construction of cascade reservoirs in the lower reaches of Jinsha River

Water temperature's cumulative effect induced by the construction of cascade reservoirs in the lower reaches of Jinsha River

Flood Control Optimization Scheduling of Cascade Reservoirs in the Middle Reaches of the Gan River Based on ECDE Algorithm

Flood Control Optimization Scheduling of Cascade Reservoirs in the Middle Reaches of the Gan River Based on ECDE Algorithm

PROTECTION AGAINST FLOODING BY FLOOD WATERS OF ALMATY AND ALMATY REGIONS

The flow of the Ile River is regulated by a cascade of reservoirs on the tributaries and along the river trunk: Bartogay ( Shelek River ), Kapshagay (Ile River), etc. The maximum flow rates along the Ile River are determined by the capa of the discharge structures of the hydroelectric power plants and the unregulated flow of the lateral inflow (Kaskelen River, etc.). The Ile River is formed by the confluence of the Tekes and Kunges Rivers, and it also receives a lot of tributaries, the sources of which flow down from the snowy peaks of the adjacent mountains. In terms of water content and turbidity, the water of the Ile River ranks third among the large rivers of Central Asia (Amu Darya, Syr Darya), and is only slightly inferior in water content to the Syr Darya River.

Macrophyte banks and fish early stages in a cascade of small hydropower reservoirs (south-eastern Brazil): temporal changes along the reproductive cycle and influence of the limnological and spatial organisation

Context Small hydroelectric power plants (SHPs) are worldwide-distributed infrastructures, the ecological impacts of which are still poorly known. Aim To evaluate the role of littoral macrophytes as nursery areas for fishes in a cascade of three SHP reservoirs in south-eastern Brazil. Methods Three random macrophyte banks, from the intermediate and lentic compartments of each reservoir, were sampled (with manual sieves and gillnets) monthly along the peak of the reproductive period. Basic limnological variables were simultaneously measured. Key results In all, 88 larvae and 393 juveniles were captured, corresponding to 29 taxa, constituting almost 30% of the regional pool of fishes in the river. Non-migrants and short-distance migrants (with or without parental care) predominated. The species accumulation curve tended to an asymptotic configuration (whole dataset sampling effort). Fish abundance differed, mainly temporally, and, at a lower degree, spatially. Higher diversity (rarefaction and extrapolation curves) occurred both at the beginning of the reproductive peak and in the first (upstream) reservoir, where there was also a good correspondence between observed and estimated richness, i.e. 90%. Conclusions The macrophyte banks in these SHP reservoirs are effectively used as nursery areas. Implications Results have provided important insights for actions of conservation and management of the local and regional ichthyofauna, in a condition where typical nursery areas do not exist.

Research on optimal scheduling of minor and moderate floods for cascade reservoirs in the lower reaches of the jinsha river considering power generation

The comprehensive cascade reservoir system is extensively used for flood control and power generation. Traditional reservoir scheduling often treats these tasks as competing objectives, prioritizing flood control during the flood season and neglecting power generation benefits. This approach, primarily applied to large floods, leads to hydraulic resource wastage and power generation loss during minor and moderate floods. The lower Jinsha River cascade reservoirs have significant flood control storage capacity, allowing part of the capacity to be used for maintaining higher water levels without compromising safety under minor and moderate floods within a 20-year return period. This paper proposes an optimal scheduling model that considers both flood control and power generation tasks for the lower Jinsha River cascade reservoirs. The Multi-objective Particle Swarm Optimization (MOPSO) algorithm was used to find non-inferior solution sets. An evaluation index system was developed to select optimal solutions under different flood frequencies, using the Minimum Discriminant Information Principle and VIKOR model. The results indicate that the optimal scheduling scheme under 20-year, 10-year, and 5-year return period floods can enhance power generation by 1.64, 1.71, and 1.35 billion kWh, respectively, compared to conventional scheduling. This approach supports coordinated flood control and power generation scheduling, contributing to the high-quality development of the Yangtze River Economic Belt.

Cascade reservoirs affected chemical compositions of dissolved organic matter and greenhouse gas dynamics in the Lancang River.

Dissolved organic matter (DOM) is an important component in aquatic systems. There has been much debate about the potential effects of cascade reservoirs on the transport and transformation of DOM. Here, through a survey of source to leave-boundary section of Lancang River (LCR) in June and November of 2017-2018, our results revealed that weak spatiotemporal variations were observed for DOC content, whereas DOM parameters were significantly different between natural and reservoir reaches. And DOM showed higher humification degree from allochthonous sources with increasing autochthonous matter in reservoir reach, may due to high particulate organic matter and releasing autochthonous DOM from phytoplankton blooms in the LCR, which can be evidenced by depleted DIC, enriched δ13CDIC and higher BIX. A unique fluorescent fraction (C5) appeared in the reservoir reach and increased along water flow, which was strongly associated with dissolved CO2 and N2O. Meanwhile, BIX value decreased with increasing dam height, hydraulic residence time (HRT), and reservoir capacity, which may promote CH4 production, highlighting variation of DOM compositions in understanding the effect of greenhouse gas (GHG) dynamics in the LCR. The findings were essential for comprehending the influences of cascade reservoirs on carbon cycle, and informed policy development for the sustainable management of transboundary water resources like the LCR.

Quantifying flood control storage substitution in cascade reservoirs

Quantifying flood control storage substitution in cascade reservoirs

Impact of cascade reservoir on the sources of organic matter in sediments of Lancang river.

The construction of dams to intercept natural rivers constitutes the most severe human activity influencing the underlying surface. This study focuses on four cascade reservoirs of the Lancang River and explores their impact on the migration of organic matter in sediments. The research reveals significant spatial variations in total organic carbon (TOC) and total nitrogen concentrations in the sediments of the four reservoirs. The carbon and nitrogen isotopes indicate that terrigenous organic matter is the main source of TOC in the sediments, contributing an average of 66.80%. Endogenous algal-derived organic matter is the second significant source, contributing between 14.30% and 32.91%. The sources contributed from upstream organic matter are the lowest, ranging from 6.36% to 15.33%. Our study demonstrates that the construction of cascade reservoirs may significantly alter the processes of material sources in the river basin ecosystem, particularly in the large reservoir which increased more endogenous algal-derived organic matter.

A deep reinforcement learning approach for joint scheduling of cascade reservoir system

A deep reinforcement learning approach for joint scheduling of cascade reservoir system

Seasonal variations and hydrological management regulate nutrient transport in cascade damming: Insights from carbon and nitrogen isotopes

Reservoirs around the world have significantly altered the natural transport of nutrients in rivers. However, the specific effects of the cascade damming on the migration, transformation, and environmental consequences of these nutrients remain unclear. To address this knowledge gap, we analyzed spatiotemporal variations in water chemistry, nutrient concentrations, stable isotope of dissolved inorganic carbon (δ13CDIC) and nitrate isotope (δ15N-NO3-) in seven cascade reservoirs along the Wujiang River, each characterized by different regulatory regimes. Our findings reveal that the average absolute changes in concentrations of total nitrogen (TN), total phosphorus (TP), and silicon dioxide (SiO2) during the wet season (WS, spring and summer) were 2.4, 1.4, and 1.1 times higher than those observed in the dry season (DS, autumn and winter). During the WS, the average apparent retention efficiency (*RETf) values in the Hongjiadu reservoir were 97 % for TN, 98 % for TP, and 95 % for SiO2, indicating substantial nutrient consumption in the cascading reservoirs. Conversely, during the DS, the *RETf values for TN, TP, and SiO2 were negative, suggesting notable nutrient accumulation within the reservoirs. The nutrient fluxes released downstream from the cascade reservoirs in the Wujiang River were significantly greater than the upstream inflow fluxes. These findings help demonstrate how downstream discharge across cascade reservoirs amplifies nutrient flux disparities due to dam construction. Our study enhances the understanding of how cascade dam construction impacts nutrient dynamics, supporting the optimization of reservoir operation models and advancing scientific water resource management and conservation efforts.

Research and Application of Characteristic Curve Correction Method for Cascade Hydropower Stations Considering Runoff Inconsistency

The situation wherein a hydrological series does satisfy the assumption of “independent and identically distributed” is called runoff inconsistency. “Flow Inversion Phenomenon” is also a kind of runoff inconsistency in space that reflects errors in the hydrological modeling process and can provide a basis for curve correction. In this paper, the causes of the flow inversion phenomenon are analyzed, and a characteristic curve correction method for hydropower stations based on runoff inconsistency is proposed. “Interval Fallacy Rate” is proposed to quantify the flow inversion phenomenon, and with the goal of minimizing the interval fallacy rate, several characteristic curve correction methods, such as single-point discrete optimization, multi-point discrete optimization, overall translation optimization and partial translation optimization, are constructed to correct the turbine characteristic curve, discharge curve, and capacity curve of a hydropower station. In the case study, we take a six-reservoir cascade reservoir system in China as an example. After curve correction, the interval fallacy rate of each interval is reduced to varying degrees. This study provides a new idea for the correction of hydropower stations’ characteristic curves in basins lacking measured flow data.

A hydrological knowledge-informed LSTM model for monthly streamflow reconstruction using distributed data: Application to typical rivers across the Tibetan plateau

Long-term streamflow data are essential for water resources planning and management, cascade reservoir scheduling, and understanding the response of water resources to climate change and human activities. Streamflow reconstructions can effectively “fill-in” missing runoff data gaps. However, considering the scarcity of observational monitoring stations and the limitations of distributed hydrological models, the reconstruction of long-term time series of runoff under varying surface and climatic conditions remains a challenge. Here, we propose a hydrological knowledge-informed Long Short-Term Memory (LSTM) model (Hydro-LSTM) for monthly streamflow reconstruction using open-access distributed data. Hydrological knowledge was derived from hydrological governing equations and parameters for each independent water cycle component. The Hydro-LSTM addresses the lack of physical consistency inherent in data-driven models, along with missing observations. The approach was applied to simulate monthly runoff of representative rivers in the Tibetan Plateau (TP) from 1980 to 2018. The results show that streamflow reconstructions for these eight stations yielded favorable levels of performance; trends in dynamic change and the range of runoff in the model training period and test period are consistent with the measured values. Values of NSE, CC, and KGE range between 0.715–0.968, 0.847–0.985, and 0.786–0.969, respectively. The influence of hydrological expertise and distributed data on the model is discussed. The introduction of hydrological knowledge makes the driving elements have hydrological significance, which improves the physical consistency and interpretability of the Hydro-LSTM model. The proposed Hydro-LSTM is expected to (1) achieve accurate and efficient reconstructions of long-term runoff time series using open-access distributed data and limited observations and (2) provide a new perspective for runoff reconstruction and prediction, with promising application prospects.

Design flood estimation of cascade reservoirs based on vine-copula flood regional composition

Study regionThe study region is the Yalong River basin, the largest tributary of the Jinsha River in China. Study focusThe most likely flood regional composition (MLFRC) method has been widely used to estimate the design flood of cascade reservoirs in the operation period, in which the Gumbel copula or t-copula is often selected to fit the theoretical joint distribution. However, the Gumbel copula is only suitable for 2 or 3 cascade reservoirs, while the t-copula has great uncertainty in parameter estimation. In this study, we introduce vine-copula into MLFRC framework to estimate design flood of cascade reservoirs, and comprehensively compare the universality of different copulas through statistical experiments and a case study on the cascade reservoirs in Yalong River basin. New hydrological insights for the regionThe results indicated that: (1) Vine-copula significantly outperforms Gumbel copula and t-copula in terms of fitting the theoretical joint distribution. (2) The vine-copula based MLFRC method can successfully solve the different flood regional composition schemes most accurately in the simulated scenarios. (3) Compared with the design floods in construction period, the design floods in operation period in the Yalong River basin decrease significantly due to the regulation of upstream reservoirs. The 1000-year design flood at basin outlet section decrease by about 40 %.

Construction of pumped storage power stations among cascade reservoirs to support the high-quality power supply of the hydro-wind-photovoltaic power generation system

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.

Distribution and sources of polycyclic aromatic hydrocarbons in cascade reservoir sediments: influence of anthropogenic activities and reservoir hydrology.

The construction of dams has caused disruptions to river connectivity, leading to alterations in the deposition of hydrophobic organic contaminants in reservoir sediments. Further investigation is warranted to explore the impact of cascade reservoirs with differing hydrological characteristics on polycyclic aromatic hydrocarbons (PAHs) distribution in sediment. This study examines the presence of 30PAHs in the sediments collected from six cascade reservoirs situated in the Wujiang River basin during January and July 2017. The results showed that Σ30PAHs ranged from 455-3000ng/g dw (mean 1030ng/g dw). Anthropogenic activities and reservoir hydrology determined the distribution trend of PAHs in sediments, with an overall increase from upstream to midstream and then a decrease downstream. The PAH levels were highly linked to the secondary industry (P < 0.05). This was further supported by the relationship between the PAH emissions from coal combustion and traffic sources analyzed by the positive matrix factorization model and economic parameters in the wet season (P < 0.01). At the same time, reservoir age (RA) showed a positive correlation with PAH concentrations (P < 0.05), while hydraulic retention time (HRT) exhibited a negative correlation with PAH levels (P = 0.03). The relationship between total organic carbon (TOC) and PAHs in stream sediments worldwide was nonlinear (P < 0.01), with PAH concentrations initially rising and then falling as TOC levels increased. Concerns regarding carcinogenic risk were raised due to contributions from coal and vehicular sources, with the risk increasing with RA.

Human interventions alter meandering channels evolution: Insights from the inner bank scouring and outer bank deposition in the Jingjiang Reach after the operation of the Three Gorges Dam

Geomorphic abnormal responses of consecutive river bends to human activities, such as reservoir constructions and bank protection projects, have not been understood sufficiently. Based on the measured hydrological and topographic data, and remote sensing data, we investigated the morphological adjustments of 17 typical consecutive bends with different curvatures (the ratio of bend width B and bend radius R at the bend apex ranging from 0.22 to 1.96) in the Jingjiang Reach after the Three Gorges Dam (TGD) (2004–2021). The results show that these bends generally experienced inner bank scouring (IBS) and outer bank deposition (OBD). The distance to the dam affects the mechanism of IBS, from being primarily controlled by the water scouring intensity near the dam to the bend curvature and the regime adjustment of the upstream bend. Our results also show that the locations of IBS and OBD in the bends are related to the bend curvature. In sharp bends (B/R > 0.5), IBS occurs in the upper half of the bend, accompanied by OBD near the bend apex. In moderate bends (B/R ≤ 0.5), IBS occurs throughout the whole bend, with OBD near the bend entrance. A higher curvature bend tends to experience greater scouring of the inner bank near the bend apex. Moreover, the effect of upstream bends on downstream bends is revealed. In response to IBS and OBD in the upstream bend, the thalweg at the entrance shifts towards the inner bank, further promoting IBS in the downstream bend. OBD in the downstream bend is intensified by the residual reverse circulation of upstream bend. The results of this study can enhance the understanding of the evolution of meandering rivers in response to human activities, and may serve as a rational reference for managing the meandering rivers downstream of cascade reservoirs.

Spatiotemporal Distribution of nirS-Type Denitrifiers in Cascade Reservoir Sediments of the Qinghai Plateau

Compared to single damming, the impact of cascade damming on nitrogen-related microorganisms in river ecosystems exhibits greater complexity. However, there is still a lack of research on the response of denitrifiers to the construction of cascade reservoirs. A study was conducted on 10 cascade reservoirs in the upper reaches of the Yellow River to investigate the impact of cascade reservoir construction on nirS-type denitrifying bacteria in sediments. Sediment samples were collected in May (dry season) and August (wet season) of 2023. The spatiotemporal characteristics of the nirS-type denitrifying bacterial community and gene abundance were analyzed using Illumina high-throughput sequencing and real-time fluorescence quantification PCR (qPCR). Redundancy analysis (RDA) and variation partitioning (VP) were utilized to assess the impact of environmental factors on these communities. The results showed the following: (1) Proteobacteria was the predominant phylum of nirS-type denitrifying bacteria in cascade reservoir sediments. At the genus level, unclassified Proteobacteria (69.51–95.64%) showed the highest relative abundance, followed by Paracoccus, Rhodanobacter, and Pseudomonas, indicating that unclassified Proteobacteria may dominate denitrification in these reservoir sediments. (2) The α and β diversity indices of nirS-type denitrifying bacteria were higher in the dry season than in the wet season, and also higher in young reservoirs compared to old reservoirs (p &lt; 0.05). (3) Temporally, the abundance of the nirS gene was significantly higher in the wet season (12.71 × 107 copies/g dry sediment) compared to the dry season (66.35 × 105 copies/g dry sediment). Spatially, the abundance of the nirS gene was higher in the central region, while relatively lower at both ends. (4) RDA and VP analysis indicated that the community structure and abundance of nirS-type denitrifying bacteria were significantly influenced by the total nitrogen in sediments (19.31%) and water temperature (14.13%). Spearman correlation analysis showed that organic carbon significantly affected the diversity of nirS-type denitrifying bacteria (p &lt; 0.05). The results contribute to a better understanding of the nitrogen-related microbial community in cascade reservoir sediments of the Yellow River, providing a scientific basis for reservoir management.