River Cascade Research Articles

New challenges regarding the environmental and sanitary condition of Ukrainian water bodies

Today Ukraine is faced with new challenges that have a significant impact on natural water bodies and aquaculture. As a result of hostilities, there is an additional pressure on aquatic ecosystems. Unfortunately, large territories with important fishery complexes of Ukraine are either occupied, located in the war zone, or mined. Currently it is impossible to carry out comprehensive monitoring investigations into the actual environmental condition of inland water bodies of Ukraine. Therefore, in order to establish a true picture of the state of the water fund of Ukraine, an analytical review of publications was performed. Unfortunately, after the large-scale hostilities on the territory of Ukraine, a significant number of water bodies changed their status according to saprobic indicators. The situation is difficult with the reservoirs of the Dnipro River Cascade, which accumulate all pollutants released into the water from the catchment area. The destruction of the Kakhovka Hydroelectric Power Station led to a massive killing of all biota, including fish. The reservoirs are mostly polluted by biogenic, organic and surface-active substances, oil products, phenols, pesticides, and heavy metals. Even in the pre-war period, the problem of water pollution required immediate decisions, and with the beginning of the full-scale war, it became one of the most urgent tasks for Ukraine. Today, Ukraine’s water bodies suffer from pollution by pyrogens, fuel, and lubricants after rocket attacks and even from the total destruction of fish farms, water reservoirs, i.e., the Kakhovka Reservoir. Therefore, monitoring of the environmental condition of inland water bodies of Ukraine will provide an opportunity to assess their real condition and, in the future, to select the complex of methods aimed for their restoration.

Short-Term Hydro-Wind-PV peak shaving scheduling using approximate hydropower output characters

With the massive construction of wind and photovoltaic (PV) power plants, the uncertainty of their output poses challenges for grid peak regulation. Hydropower, characterized by convenient regulation, fast response speed, and low cost, is an ideal choice for compensating for wind and PV energy generation. Mixed-Integer Linear Programming (MILP) is employed to work out short-term scheduling of hydro-wind-PV power. However, considering hydropower scheduling alone is already highly complex, and incorporating the deviations in wind and PV energy further reduces the solution efficiency. In practical scheduling, operators often rely on empirical scheduling methods that can yield satisfactory results. To enhance solution quality and improve the scalability and efficiency of the MILP method, a short-term optimization scheduling model for hydropower plants has been proposed and applied to the Hongshui River cascade system. The case study shows that the model can perform calculations in just 2 s, demonstrating extremely high computational efficiency. This can significantly enhance decision-making in cascaded hydropower scheduling. At the same time, the model leaves sufficient reserve capacity to address the uncertainty of wind and solar power output while reducing the residual load by 0.8 %, which is beneficial for the stable operation of the grid.

Spatiotemporal patterns and co-occurrence patterns of dissimilatory nitrate reduction to ammonium community in sediments of the Lancang River cascade reservoirs.

Dissimilatory nitrate reduction to ammonium (DNRA) is an important nitrate reduction pathway in freshwater sediments. Many studies have focused on the DNRA process in various natural habitats. However, the joint operation of cascade reservoirs will affect the physical and chemical properties of sediments, which may change the DNRA process and bacterial community pattern in the surface sediments of cascade reservoirs. Our study was the first to investigate the spatiotemporal distribution patterns of potential DNRA rate, nrfA gene abundances, and DNRA bacterial community diversity in surface sediments of the Lancang River cascade reservoirs. The results of slurry incubation experiments combined with the 15N isotope tracer experiment ascertained that the potential rates of DNRA were 0.01-0.15 nmol-N cm-3 h-1, and qPCR results indicated that the abundance range of nrfA was 1.08 × 105-2.51 × 106 copies g-1 dry weight. High throughput sequencing of the nrfA gene revealed that the relative abundance of Anaeromyxobacter (4.52% on average), Polyangium (4.09%), Archangium (1.86%), Geobacter (1.34%), and Lacunisphaera (1.32%) were high. Pearson and RDA correlation analysis exhibited that nrfA gene abundance was positively correlated with altitude, pH, OC, and sand concentration. Anaeromyxobacter was positively correlated with reservoir age and DNRA potential rate. The deterministic environmental selection process plays a crucial role in the formation of the DNRA bacterial community. Network analysis displayed that the dominant DNRA genus was the key population of the DNRA microbial community in the sediments of Lancang River cascade reservoirs. This study reveals that the variation of DNRA bacterial activity and community structure is largely driven by the construction of cascade reservoirs, and provides a new idea for further understanding the characteristics of the DNRA community in the cascade reservoir ecosystem.

Water Supply Strategy of Cascade Reservoirs for Irrigation and Industrial Uses Based on Marginal Benefit

The operation of reservoir is to optimize the utilization of water resources and bring its maximum benefit. Most studies of reservoir scheduling generally pursue the maximization of revenue, and rarely consider the demand of water supply from reservoirs to agriculture or factories in the scheduling process. The few studies that have taken this into account have included this demand in the objective function or constraint, rather than in terms of marginal benefits. This work presents a method to determine water supply decision of reservoir based on marginal benefit. By iteratively linearizing the cascaded reservoir scheduling model and calculating the optimal solution to the dual problem of the model, this method provides a reference for the water supply plan of reservoir to agricultural departments and factories. The proposed method has been applied to 8 reservoirs on the Jinsha River cascade. Convergence in water head is achieved after 15 iterations, and numerical comparisons of the marginal value of water resources at different locations and periods across various reservoirs are obtained.

Chlorophyll Content and Photosynthetic Activity of Phytoplankton in Reservoirs of the Volga River (Russia)

Using the fluorescent method in the modification of Krasnoyarsk State University, we studied the development (as chlorophyll content, ∑CHL) and photosynthetic activity of phytoplankton in seven large flat reservoirs of the Volga River cascade (Russia) in August 2015–2017. In the period of the maximal warming of water, average ∑CHL varied in limits of 19.4–33.7 μg L−1 in the Upper Volga, 8.5–27.8 μg L−1 in the Middle Volga, and 5.2–11.3 μg L−1 in the Lower Volga. The photosynthetic activity coefficient (PhAC) varied mostly in limits of 0.12–0.59, with an average of 0.22–0.38 and only in 2017 decreased to minimal < 0.10 and average < 0.20. The average PhAC values show the normal physiological state of the phytoplankton of the Upper Volga during all periods of observation, with an occasional decrease in PhAC in the Middle Volga and low photosynthetic activity in the Lower Volga. A decrease in the average ∑Chl and PhAC in 2017 was under cyclonic windy weather with a large amount of precipitation, low solar radiation, and large volume of flow. A trend towards a decrease in ∑CHL, like a decrease in PhAC from the Upper Volga to the Lower Volga, is explained by an increase in the flow rate and volume of runoff downstream of the Volga River.

Study on the migration law of biogenic substances under different scheduling schemes of reservoirs

In order to study the migration process of biogenic substances in river basins under reservoir regulation and quantify the migration characteristics of nitrogen and phosphorus pollution in the middle and lower reaches of the Lancang River cascade reservoir basin. This article constructs a simulation model for the migration of biogenic substances in the Lancang River Basin based on the SWAT model, and preliminarily simulates the migration process of nitrogen and phosphorus in the basin. The results indicate that the model has good applicability in the Lancang River basin, with the NSE coefficient of 0.76 and the R2 coefficient of 0.78. Moreover, there is a roughly positive correlation between nitrogen and phosphorus production and rainfall distribution in the basin, but rainfall is not the only factor determining the distribution of nitrogen and phosphorus pollution load. By inputting different reservoir regulation schemes into the reservoir regulation module, the migration processes of nitrogen and phosphorus in various sections of the watershed under natural conditions, conventional regulation, power generation regulation, and ecological regulation schemes are calculated. The results indicate that the conventional and power generation scheduling schemes have a significant impact on the migration of total nitrogen and phosphorus in the watershed, leading to a certain retention and accumulation effect of nitrogen and phosphorus in the reservoir. However, the ecological scheduling scheme to some extent reduces the impact of reservoir scheduling on the migration of biogenic substances.

Effects of water temperature on swimming performance of Siniperca knerii Garman under the Yuanshui River cascade development

We examined the swimming parameters and oxygen consumption rate at four temperature levels (15，20，25 and 30°C) of Siniperca knerii Garman (11.81 ±2.21 cm, 26.4 ± 6.28g) from Yuanshui River for 30 days to analyze the ecological adaptability of the typical fish and the conservation of fishery resources from the Dongting Lake water system. Their relationship was also analyzed, and the results showed an approximately linear increasing trend of the fish’s critical swimming speed and preferred swimming speed with the change of temperature (P<0.05). In contrast, the induction velocity of fish decreased with the increase in water temperature. The relative induction velocities of the fish at four temperatures were (1.16±0.07), (0.94±0.06), (0.86±0.07), and (0.70±0.09) BL/s (Body Length/s). The preferred swimming speed was (1.86±0.04), (2.23±0.35), (2.65±0.28), and (2.74±0.33) BL/s. The relative critical speed was (2.58 ±0.32), (3.31±0.41), (4.31±0.52), and (5.22±0.48) BL/s. According to oxygen consumption rate at different temperatures, four nonlinear function models of the relationship between oxygen consumption rate of water temperature and swimming speed behavior parameters were obtained by nonlinear fitting. The model proved that the oxygen consumption rate, tail beating frequency, and respiratory rate increased with the increase in swimming speed. The higher the temperature, the more significant the changes were. The results showed that water temperature significantly affected the swimming characteristics of juvenile Siniperca knerii Garman. The changes were due to physiological and biochemical regulation with temperature and environmental changes. This experiment provided essential data support for the adaptive mechanism of sports physiology and ecology of typical fishes in the Yuanshui River.

Community composition and abundance of complete ammonia oxidation (comammox) bacteria in the Lancang River cascade reservoir

The construction of the reservoir has changed the nitrogen migration and transformation processes in the river, and a large amount of sediment deposition in the reservoir may also lead to the spatial differentiation of complete ammonia oxidation (comammox) bacteria. The study investigated the abundance and diversity of comammox bacteria in the sediments of three cascade reservoirs, namely, Xiaowan, Manwan, and Nuozhadu on the Lancang River in China. In these reservoirs, the average amoA gene abundance of clade A and clade B of comammox bacteria, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB) was 4.16 ± 0.85 × 105, 1.15 ± 0.33 × 105, 7.39 ± 2.31 × 104, and 3.28 ± 0.99 × 105 copies g−1, respectively. The abundance of clade A was higher than that of other ammonia oxidizing microorganisms. The spatial variation of comammox bacteria abundance differed among different reservoirs, but the spatial variation trends of the two clades of comammox bacteria in the same reservoir were similar. At each sampling point, clade A1, clade A2, and clade B coexisted, and clade A2 was usually the dominant species. The connection between comammox bacteria in the pre-dam sediments was looser than that in non-pre-dam sediments, and comammox bacteria in pre-dam sediments exhibited a simpler network structure. The main factor affecting comammox bacteria abundance was NH4+-N, while altitude, temperature, and conductivity of overlying water were the main factors affecting comammox bacteria diversity. Environmental changes caused by differences in the spatial distribution of these cascade reservoirs may be the main driver of the changes of community composition and abundance of comammox bacteria. This study confirms that the construction of cascade reservoirs results in niche spatial differentiation of comammox bacteria.

Calculation and evaluation of suitable ecological flows for eco-environmental recovery of cascade-developed rivers

River cascade development affects the hydrological and habitat characteristics of the region and disrupts the dynamic balance of stable river ecosystems. The most profound impact of river cascade development is on the resident fish species. River ecosystem restoration for maximum river habitat improvement is generally based on water security and environment improvement and effectively embodies the nature-based solutions (NbS) concept of naturalized restoration. Yuanjiang (Y.J.) River is an international river in southwest China seriously affected by cascade development. By determining the response of the river ecosystem and using the key performance indicator method, Yuanjiang carp (Cyprinus carpio rubrofuscus) and red giant catfish (Bagarius rutilus) were identified as the key species in the main stream of the Y.J. River., and the ecological effects of river cascade development on them were studied by applying two-dimensional hydrodynamic physical habitat simulation and multi-objective ecological scheduling models. Based on the calculation results for ecological operation optimization of cascade reservoirs, an improved progressive optimality algorithm was used to calculate the ecological flows required to maintain the stability of the river ecosystem. With the increasing extent of cascade development in the river, important indicators, such as the intra-annual, extreme, high, and low flows have changed significantly, and the hydrological characteristics of the main stream have changed rapidly and comprehensively. Habitat suitability curves were used to determine the appropriate water depth and delineate the weighted usable area required for the spawning, nursing, and growing periods of the key fish species. The suitable ecological flows required for the three life-cycle stages of the C. carpio rubrofuscus accounted for 34, 45, and 62 %, respectively, of the multi-year mean natural water inflow at the Qiaotou (Q.T.) cascade, whereas those required for the three respective periods of B. rutilus accounted for 47, 98, and 27 %, respectively, of the multi-year mean natural water inflow at the Madushan (M.D·S.) cascade. Considering the physiological lifecycle demands of the indicator/key fish species and the upper limit of water resources development and utilization in the key river section, the ecological flow precipitation frequency in the Q.T.-Luodie (Q.T.-L.D.) and M.D·S.-Xinjie (M.D·S.-X.J.) sections (currently at 25, 50, and 75 %, respectively) can be increased to 100 % under optimal operating conditions (cascade hydropower station optimal operation). After implementing the multi-objective ecological operation at the Y.J. River main-stream cascade reservoirs, the suitable habitat area for C. carpio rubrofuscus and B. rutilus increased significantly (>10 % and 15 %, respectively). In general, the NbS-based ecological flow calculation method for cascade-developed rivers has a wide range of applications, which can be useful for the eco-environment restoration of rivers and improving the living habitats of waterway organisms.

Comprehensive study on cascade hydropower stations in the lower reaches of Yalong river for power generation and ecology

According to the construction of the cascade hydropower stations in the lower reaches of the Yalong River and the ecological environment condition of the river, a medium and long-term optimal dispatching model with the goal of maximizing the power generation benefits of the cascade hydropower stations is established, and the dynamic programming method is used to optimize the solution, so as to obtain the ten-day average maximum power generation of cascade hydropower stations. According to the latest relevant research at home and abroad, it is found that during the power generation process of the hydropower station, the discharge will produce certain greenhouse gas (GHG) emissions during the delivery process. In this paper, the greenhouse gas emissions existing in the power generation process of cascade reservoirs are considered, and the typical values are selected to calculate the average greenhouse gas (mainly CO2) emissions from 2001 to 2018, twelve plants with strong carbon sequestration and oxygen release capacity and suitable for growing in the basin are selected, and the mitigation and improvement measures of greenhouse gas emissions around the reservoirs in the basin are given. A new research idea is provided for the Yalong River cascade reservoirs to focus on the power generation benefits while reducing the greenhouse gas emission situation to a certain extent.

Spatial Distribution and Risk Assessment of Heavy Metals in Surface Sediments from the Middle and Upper Reaches of the Yangtze River

The hydrological regime of rivers significantly changes after dam impoundment, which in turn affects the particle composition and heavy metal fractions of the river sediments. From June to July 2019, the sediments from 26 sampling sections were collected along the main stream of the Yangtze River from Panzhihua City in the upper reaches of the Yangtze River to Hukou City in the middle reaches of the Yangtze River. The concentrations and fractions of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn were measured using the BCR three-step extraction procedure. The pollution status and potential ecological risk of heavy metals in sediments were evaluated using the geo-accumulation index, the sediment quality guideline, and the risk assessment coding method (RAC). The results showed that the average particle size of sediments in the upper reaches of the Yangtze River (Jinsha River cascade reservoir section and the Three Gorges reservoir section) decreased from upstream to downstream, the total concentrations of As and Zn increased, and the variation trend in the middle reaches was not obvious. The content of clay particles was significantly positively correlated with the acid-soluble fraction concentrations of Cd and Ni. Cd was mainly in the residual fraction (59.26%) and acid-soluble fraction (24.67%). Large parts of Cr and Ni were residual fractions accounting for 92.41% and 83.41%, respectively. As, Co, Cu, Pb, and Zn were mainly in the residual fraction and the reducible fraction. The order of decrease for the pollution degree (Igeo) of As, Cd, Co, Cr, Ni, and Zn was the Jinsha River, the middle reaches of the Yangtze River, and the Three Gorges Reservoir. The decrease order of bioavailability (RAC) of Cd, Co, Cr, Cu, Ni, and Zn was the Three Gorges Reservoir, the Jinsha River, and the middle reaches of the Yangtze River. The bioavailability of As and Pb decreased in the order of the middle reaches of the Yangtze River, the Three Gorges, and the Jinsha River. According to the classification of the RAC, Cd in the Three Gorges Reservoir area exhibited a high risk with the RAC accounting for 48.44%. Cu, Ni, and Zn showed a low or medium risk.

Spatial patterns in water quality and source apportionment in a typical cascade development river southwestern China using PMF modeling and multivariate statistical techniques

River cascade development is one of the human activities that have the most significant impact on the water environment. However, the mechanism of cascade development affecting river hydrochemical components still needs to be further studied. In this study, water quality index(WQI), positive matrix factorization(PMF) model and multivariate statistical techniques were used to identify the mechanism of cascade development affecting river hydrochemical components in an typical cascade development Rivers, Lancang River, China. The results showed that the water quality of Lancang River is relatively good due to less affected by human activity. The spatial variation of river hydrochemistry is affected by the development of cascade reservoirs, and shows three patterns: irregular variation (pH and DO), fluctuating decreasing (Na+, Cl−, SO42− and HCO3−) and multi-peak variation (TN, TDN, NO3−-N and NH4+-N). It's worth noting that the concentration of the most hydrochemical parameters is higher in the upper reaches (less human activities) than that in the middle and lower reaches of river due to the retention effect of the reservoir on the chemical composition. The PMF model outputs revealed that the rock weathering and internal source, sewage and soil nitrogen, and chemical fertilizer were primary material sources of Lancang River. Compared with the natural channel zone (41.0%), the interaction of water-rock has more influence on chemical component in the reservoir area (56.3%), while the contribution of fertilizer (11.2%) to the river hydrochemistry is less. The sites of downstream of the reservoir dam were affected by the retention of the reservoir and the disturbance of the bottom drainage, which leads to the weakening of the influence of the sewage (44.7%) on the river material and the increase of the contribution of fertilizer (25.0%). These results could provide valuable information in controlling the eutrophication of cascade reservoirs and the scientific construction of river cascade reservoirs.

Research on Operation Mode of the Yalong River Cascade Reservoirs Based on Improved Stochastic Fractal Search Algorithm

With the completion of the Lianghekou Reservoir, with a multiyear regulation capacity, the operation relationship of the cascade reservoirs in the Yalong River is becoming increasingly complex. In order to study an optimal operation mode of the cascade reservoirs in the Yalong River under different inflow frequencies, based on the shortcomings of the existing single reservoir operation mode and the local joint operation mode of the cascade reservoirs, this paper first proposed a global joint operation mode for the cascade reservoirs to develop the power generation potential of daily regulating reservoirs and then gave a solution method for the cascade reservoirs’ operational model based on an improved stochastic fractal search (ISFS) algorithm. Finally, taking the maximum power generation as the goal and the inflow data of five typical years as the model inputs, this paper analyzed the differences in the power generation and water abandonment results of the cascade reservoirs in the middle and lower reaches of the Yalong River under the above three operation modes. The results show that (1) compared with the stochastic fractal search (SFS) algorithm and the particle swarm optimization (PSO) algorithm, the ISFS algorithm had faster convergence speed and higher precision; (2) the global joint operation mode had a more significant optimization effect in the year with more inflow, followed by the local joint operation mode, and the single reservoir operation mode had the worst; however, the difference in the results of the three operation modes gradually decreased as the inflows gradually decreased.

Generation expansion planning for Guizhou province based on the complementary characteristics of wind and solar

With the growth of wind power and solar power, power source clean transformation has become a feasible way for achieving the carbon peak target. As a hydropower resource-abundant province, Guizhou has already built Wujiang river cascade hydropower plants. This paper introduces the basic information of the Guizhou provincial power system and geometrical renewable resource distribution characteristics, especially the power source structure. Then, the wind and solar power complementary characteristics are analyzed by different copula conjunction functions. Then, the power structure transformation and generation expansion plan are provided with both carbon peak restriction and curtailment restrictions. At last, the future Guizhou provincial power system in 2029 operation simulation cases are provided, which can reduce the thermal power generation ratio to 42% and increase wind and solar power generation ratio to 8.5% and 13% approximately. The conclusion indicates that coal-fired power plant flexible reform and larger capacity energy storage installation effectively solve the larger power fluctuation and peak regulation demand with more renewable energy integration target.

Energy Storage Benefits Assessment Using Multiple-Choice Criteria: The Case of Drini River Cascade, Albania

Albania’s electricity sector lacks energy storage systems (ESS); hence, large quantities of electricity generated during the off-peak time, and excess electricity cannot be stored. On the other hand, the transmission capacity upgrades do not keep pace with the growth in peak electric demand; thus, congestion-related issues occur. Congestion of transmission lines has led to considerable uncertainties. Drin River cascade is located north of Albania. It possesses enormous potential energy that is not used due to a lack of ESS. Security of supply, rational use of renewable energy sources (RES), diversification of the electricity sector, increased competitiveness, sheltering more future RES capacities that can benefit from deferring investment in the existing transmission system, and environmental protection are some of these the main benefits of integrating ESS. Regarding the energy transition, the Albanian government’s endeavor aims to maintain and further develop a flexible, sustainable, secure, efficiently supplied, and affordable energy supply system. The results of the simulation executed by using ES-select software to produce multiple benefits from a single device from the chosen application’s list (App1–App6) showed that the most adequate ESS for storing excess electricity in the Drin River cascade are: compressed air energy storage (CAES-c), pumped hydro energy storage (PHES), and sodium-sulfur batteries (NaS). Integrating such systems in the central or bulk generation makes the circumvented cost in 10 years profitable; therefore, moving towards 2030, it would be extremely difficult to tackle the energy sector’s challenges alone, without integrating the ESS.

Spatial and Seasonal Patterns of Sediment Bacterial Communities in Large River Cascade Reservoirs: Drivers, Assembly Processes, and Co-occurrence Relationship.

Sediment bacteria play an irreplaceable role in promoting the function and biogeochemical cycle of the freshwater ecosystem; however, little is known about their biogeographical patterns and community assembly mechanisms in large river suffering from cascade development. Here, we investigated the spatiotemporal distribution patterns of bacterial communities employing next-generation sequencing analysis and multivariate statistical analyses from the Lancang River cascade reservoirs during summer and winter. We found that sediment bacterial composition has a significant seasonal turnover due to the modification of cascade reservoirs operation mode, and the spatial consistency of biogeographical models (including distance-decay relationship and covariation of community composition with geographical distance) also has subtle changes. The linear regression between the dissimilarity of bacterial communities in sediments, geographical and environmental distance showed that the synergistic effects of geographical and environmental factors explained the influence on bacterial communities. Furthermore, the environmental difference explained little variations (19.40%) in community structure, implying the homogeneity of environmental conditions across the cascade reservoirs of Lancang River. From the quantification of the ecological process, the homogeneous selection was recognized as the dominating factor of bacterial community assembly. The co-occurrence topological network analyses showed that the key genera were more important than the most connected genera. In general, the assembly of bacterial communities in sediment of cascade reservoirs was mediated by both deterministic and stochastic processes and is always dominated by homogeneous selection with the seasonal switching, but the effects of dispersal limitation and ecological drift cannot be ignored.

Feasibility of pumped hydro energy storage in a river cascade - case study of the Meuse

The Meuse river in the Netherlands has been made navigable by the construction of a cascade of seven low head weirs. Because of environmental regulations, hydropower facilities exist at only two weirs. This implies the full hydropower potential of the Meuse cascade is not utilized. By using pump-turbines the river sections upstream of the weirs could be additionally usable as energy storage reservoirs and could improve and ensure river navigability under changed climate conditions. The main goal of this study is to assess the possible utilization of the full energy storage- and hydropower potential of the Meuse cascade within Dutch environmental regulations. The novelty of this study is the evaluation of the concept of using canalized river sections for pumped-storage purposes within conditions of fluctuating discharge and -water levels throughout the year. In order to meet the goal of the study the relatively fish-friendly Archimedean screw has been selected as pump-turbine. Next a conceptual design of a pumped-storage hydropower plant equipped with screws has been compiled. By using this design, the assessment of utilizing the hydropower- and energy storage potential of the cascade has been carried out by constructing and applying a numerical model. The study shows it is possible to utilize the full hydropower- and the majority of the energy storage potential of the Meuse cascade. The cumulative installed turbine capacity for the cascade turns out to be 81 MW. The Annual Energy Yield (AEY) from regular hydropower alone is 225 GWh. In addition, the yearly surplus power that can be processed for energy storage purposes is 137.2 GWh, of which 77.2 GWh is returned to the grid by a round-trip efficiency of 56.25 %. In total 302.2 GWh can be delivered to the grid which can power up to 75.000 households. The specific cost is relatively high: roughly 15,000 euro/kW. The method developed here can be applied to evaluate the storage- and hydropower potential of other canalized rivers as well, such as the upper Mississippi.

Stochastic generation of runoff series for multiple reservoirs based on generative adversarial networks

The implicit stochastic optimization (ISO) model is a methodology that has been extensively employed in the mid-long term optimal operation of a reservoir system. The generation of runoff series is the key technology to make up for the poor representativeness and reliability of historical runoff samples and is the premise to guarantee the accuracy of the ISO model. However, the traditional methods are not suitable for the stochastic generation of runoff series, among reservoirs with spatial–temporal correlation. In this work, the generative adversarial network called DC-WGAN is developed as a runoff generation model. DC-WGAN is based on a data-driven model and can capture the correlation of runoff series in time and space dimensions simultaneously. The proposed method is applied to the downstream Jinsha river cascade and Three Gorges cascade reservoirs in China to generate ten-day runoff series and is compared with the stochastic generation method based on Copula function. The focus of this paper is the model's performance in replicating the spatial–temporal correlation of ten-day runoff series. Results are as follows. (1) DC-WGAN has strong learning and generalization ability, which can learn the correct distribution of original runoff samples and generate runoff series similar to that from the validation set. (2) The runoff series among reservoirs with spatial–temporal correlation can be generated through DC-WGAN without assuming the probability distribution of samples in advance. (3) DC-WGAN is better than Copula function in capturing the spatial–temporal correlation, especially the moderate and weak correlation. The proposed methodology has a high practical value and application prospect for the stochastic generation of runoff series with spatial–temporal correlation.

DISTRIBUTION OF ALIEN SPECIES OF MACROZOOBENTHOS AND THE SPECIES COENOTIC COMPLEXES IN THE KAMA RESERVOIRS

The results of studies on the distribution of alien species in macrozoobenthic communities in the reservoirs of the Kama River cascade are provided. Twenty five alien species of the Ponto-Caspian and Ponto-Azov origins and 1 species - a representative of the Lake Baikal fauna - were registered. Differences in the species composition and structural characteristics of invaders of macrozoobenthos in the Kama and Volga reservoirs were shown. It was noted that mollusks of the genus Dreissena dominate in biomass in most of the studied biotopes. Three types of coenotic complexes of alien species have been identified: psammorelophilic profundal, characteristic for the Nizhnekamsk Reservoir and the Volgo-Kamsky and Kamsky reaches of the Kuibyshev Reservoir; the psammorelophilic coastal in Nizhnekamsk Reservoir; and the psammorelophilic coastal in Votkinsk and Kama reservoirs.

Cascade hydropower station risk operation under the condition of inflow uncertainty

Runoff is an important basis for the operation of hydropower. However, due to inflow uncertainty, the ideal practical operation process usually doesn't match with the plan, which exacerbates the power generation and ecological risks. Therefore, the purpose of this paper is to investigate the relationship between hydropower generation, ecology and their risks under the uncertainty of inflow. Gibbs sampling based on the copula function is presented to simulate the runoff. The scenario tree method is employed to describe the inflow uncertainty. The power generation risk operation model is developed based on the Mean-variance method. In addition, the expected minimum ecological risk model and its comparison model are proposed to analyze the relationship between power generation and ecological risk. The proposed methods are applied to a case study of the Lancang River cascade hydropower station. The results show that (1) The power generation risk of risk operation model decreased by 86.41% at the 90% scenario reduction level, compared with deterministic model. (2) There is an obvious competitive relationship between ecology and power generation, in the case of a 1% loss of expected power generation, the expected ecological risk can be reduced by 6.14%.