Calculation and Evaluation of Ecological Flow of Hydropower Station Based on Fuzzy Evaluation Model

The reasonable determination of ecological flow is of 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 m 3/s,and the suitable ecological flow rate was at 0.56-4.94 m 3/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.

A general multi-objective programming model for minimum ecological flow or water level of inland water bodies

Assessment of ecological flow or water level for water bodies is important for the protection of de- graded or degrading ecosystems caused by water shortage in arid regions, and it has become a key issue in water resources planning. In the past several decades, many methods have been proposed to assess ecological flow for rivers and ecological water level for lakes or wetlands. To balance water uses by human and ecosystems, we proposed a general multi-objective programming model to determine minimum ecological flow or water level for inland water bodies, where two objectives are water index for human and habitat index for ecosystems, respectively Using the weighted sum method for multi-objective optimization, minimum ecological flow or water level can be determined from the breakpoint in the water index-habitat index curve, which is similar to the slope method to de- termine minimum ecological flow from wetted perimeter-discharge curve. However, the general multi-objective programming model is superior to the slope method in its physical meaning and calculation method. This model provides a general analysis method for ecological water uses of different inland water bodies, and can be used to define minimum ecological flow or water level by choosing appropriate water and habitat indices. Several com- monly used flow or water level assessment methods were found to be special cases of the general model, including the wetted perimeter method and the multi-objective physical habitat simulation method for ecological river flow, the inundated forest width method for regeneration flow of floodplain forest and the lake surface area method for eco- logical lake level. These methods were applied to determine minimum ecological flow or water level for two repre- sentative rivers and a lake in northern Xinjiang of China, including minimum ecological flow for the Ertix River, minimum regeneration flow for floodplain forest along the midstream of Kaxgar River, and minimum ecological lake level for the Ebinur Lake. The results illustrated the versatility of the general model, and can provide references for water resources planning and ecosystem protection for these rivers and lake.

Inducing Flow Velocities to Manage Fish Reproduction in Regulated Rivers

Conservation of endangered or economic fish and control of invasive fish is a great challenge of hydraulic engineering worldwide.Flow velocity has been recognized to affect the spawning of fishes delivering drifting eggs in rivers.However,solid scientific supports and associated mechanisms to establish quantitative relations between flow velocity and fish reproduction,taking into account spawning,fertilizing,hatching,as well as surviving,are lacking.In this paper,we quantified the relationship between flow velocity and reproduction of Chinese carps through both lab and field experiments.The results showed that a minimum velocity was required to trigger Hypophthalmichthys molitrix(H.molitrix)releasing eggs,and a velocity range was preferred to sustain spawning activity.However,the embryo incubation and larvae development of H.molitrix were found to be inhibited with the increase in flow velocity.Considering the requirements of spawning and hatching,as well as larvae surviving,an optimized flow velocity processes was identified for the reproduction of H.molitrix in rivers.These findings were of great significance to the adaptive operation of reservoirs to create reasonable and precise ecological flows for managing fish reproduction,as shown by the promising results in the engineering application to the Three Gorges Reservoir.

Bridging gaps between environmental flows theory and practices in China

In recent decades,a series of policies and practices for environmental flows(e-flows)have been implemented in China,with the sustainable development goal of balancing the utilization and protection of water resources among social,economic,and ecological needs.The aims of this study were to determine the main challenges and issues in e-flows implementation at different scales by analyzing policies and practices for eflows in China,and to propose some recommendations for bridging the gaps between the science and implementation of e-flows.The gaps between the science and implementation of e-flows were found after review of literature,policies,and practices,and it was found that ecological flow was a more widely used term by the government,rather than e-flows,in implementation.The plans and effects of e-flows implementation are discussed in this paper and challenges of e-flows implementation are recognized:(1)limited water resources and uneven spatial and temporal distribution,(2)a weak scientific basis for e-flows implementation,(3)poor operability of e-flows science,and(4)ineffective supervision and guarantee measures.The recommendations are(1)to strengthen the scientific foundation of e-flows,(2)to improve effectiveness in application of e-flows science,and(3)to propose operable and effective supervision and guarantee measures.This paper elaborates the current understanding of e-flows science and provides practical recommendations for implementing e-flows and for improving the effectiveness in e-flows implementation.To bridge the gaps between science and implementation of e-flows and improve the operability of policies in future practices,more scientific research on practices is recommended through adaptive management.

The Instream Ecological Water Flow Research at the Lower Reach of Guanting Reservoir on Yongdinghe River,Beijing

作为北京市母亲河的永定河自上个世纪80年代以来三家店以下一直处于断流,河床裸露、河道两岸土地沙化严重,是北京春季沙尘天气的主要沙源之一,由于地下水超采严重,加之无水补给地下水,使得北京西部地区第四纪地下水已经基本枯竭,永定河的生态系统已经受到严重破坏。要想恢复或治理受损的河道生态环境,作为生态系统中最活跃最重要的水分多少要先算清楚。本文采用湿周法计算了永定河官厅水库下游三个控制断面（官厅水库（坝下）、雁翅、卢沟桥）的河道内生态需水流量,计算结果为:官厅水库（坝下）站的河道内流量为3.7m3 s-1。（平水年P=50%,1978年）,占年平均流量的20.7%,雁翅站的河道内流量为4.1m3 s-1（平水年P=50%,1981年）,占年平均流量的20.1%,卢沟桥站的河道内流量为1.3m3 s-1（平水年P=50%,1978年）,占年平均流量的22.1%。若能按照计算的流量来补充河道水量,即可使永定河恢复其基本的生态功能,按照Tennant法的标准,基本能使当地的河道生态系统处于较为良好的状态。

An environmental flow assessment method based on the relationships between flow and ecological response: A case study of the Three Gorges Reservoir and its downstream reach

The current environmental flow assessment of Chinese rivers is thought to have three shortcomings: The first is that environmental flow requirements of reservoirs in dammed rivers are usually not explicitly considered; the second is that enough attentions have not been paid to the inherent links between flow regime and ecological processes; the third is that most studies focus on the variable range of merely one hydrological element such as discharge needed by riverine ecosystems. Here, first proposed is a holistic method for environmental flow assessment, the flow-ecological response relationship method that is suitable for large rivers with relatively abundant ecological data. Based on the conceptual models and quantitative relationships between flow and ecological response, this method comprehensively considers the ecological conservation requirements of both reservoir and its downstream reach. Then, it is applied to assessing the environmental flows of the Three Gorges Reservoir and its downstream reach by the following steps: 1) Construction of conceptual models of flow-ecological response; 2) identification of ecological targets of environmental flows and their key periods; 3) development of the quantitative relationships between hydrological indicators and ecological indictors; 4) preliminary assessment of environmental flow according to the tradeoff between ecological targets and water demands of human. The environmental flow hydrographs obtained have explicit ecological conservation targets, time schedule of achieving each target, and characteristics of multiple hydrological elements such as flow, water level, frequency, timing, duration and rate of change. The case study has tested the reasonability and feasibility of this method, and the results of this study are expected to provide technical support and decision reference for improving the operation of the Three Gorges-Gezhouba cascade reservoirs.

Core concepts of landscape ecology

People from different backgrounds may have various opinions and methods dealing with landscape ecology. As a basic ecology theory for decision making in land use planning and resource management, it should provide sound scientific principles, which means some core concepts for landscape ecology need to be established. This paper attempts to introduce some core concepts for landscape ecology, with brief analysis, including: the integrity of landscape system and the heterogeneity of landscape elements; scale in landscape ecology; mosaics of landscape structure; spatial aggregation and spread of ecological flow; physical cultural nature of landscape; the irreversible and human dominated landscape evolution; the multi value of landscape.

Effects of Mountain Rivers Cascade Hydropower Stations on Water Ecosystems

China is rich in hydropower resources,and mountain rivers have abundant water resources and huge development potential,which have a profound impact on the pattern of water resources allocation in China.As the main way of water resources and hydropower development,the construction of cascade hydropower stations,while meeting the requirements of water resources utilization for social development,has also brought adverse effects on river ecosystems.Therefore,the impact of the construction of cascade hydropower stations on mountainous river ecosystems,where the minimum ecological flow of rivers must be ensured and reviewed.In addition,this paper proposed the deficiencies and outlooks for cascade hydropower stations based on previous research results.

Ecologically-friendly operation scheme for the Jinping cascaded reservoirs in the Yalongjiang River, China

Ecologically-friendly reservoir operation pro- cedures aim to conserve key ecosystem properties in the rivers, while minimizing the sacrifice of socioeconomic interests. This study focused on the Jinping cascaded reservoirs as a case study. An optimization model was developed to explore a balance between the ecological flow requirement （EFR） of a target fish species （Schizothorax chongi） in the dewatered natural channel section, and annual power production. The EFR for the channel was determined by the Tennant method and a fish habitat model, respectively. The optimization model was solved by using an adaptive real-coded genetic algorithm. Several operation scenarios corresponding to the ecological flow series were evaluated using the optimization model. Through comparisons, an optimal operational scheme, which combines relatively low power production loss with a preferred ecological flow regime in the dewatered channel, is proposed for the cascaded reservoirs. Under the recommended scheme, the discharge into the Dahewan river reach in the dry season ranges from 36 to 50 m3/s. This will enable at least 50% of the target fish habitats in the channel to be conserved, at a cost of only 2.5% annual power production loss. The study demonstrates that the use of EFRs is an efficient approach to the optimization of reservoir operation in an ecologically friendly way. Similar modeling, for other important fish species and ecosystem functions, supplemented by field validation of results, is needed in order to secure the long-term conservation of the affected river ecosystem.

A holistic approach for evaluating ecological water allocation in the Yellow River Basin of China

The characteristics and sustainable management of water resources on a basin scale require that they should be managed using a holistic approach.In this study,a holistic methodology called the holistic approach in a basin scale(HABS)is proposed to determine the ecological water requirements of a whole basin.There are three principles in HABS.First,ecological water requirements in a basin scale indicate not only the coupling of hydrological and ecological systems,but also the exchange of matter and energy between each ecological type through all kinds of physical geography processes.Second,ecological water requirements can be divided into different types according to their functions,and water requirements of different types are compatible.Third,ecological water requirements are related to a multiple system including water quality,water quantity,and time and space,which interact with each other.The holistic approach in a basin scale was then used in the Yellow River Basin and it suggested that 265.0x108 m3 of water,45%of the total surface water resources,should be allocated to ecological systems,such as rivers,lakes,wetlands and cities,to sustain its function and health.The ecological water requirements of inside river systems and outside river systems were respectively 261.0×10^(8) and 3.65×10^(8)m^(3).

Quantifying relations between altered hydrology and fish community responses for streams in Minnesota

Background:Altered hydrology is a stressor on aquatic life,but quantitative relations between specific aspects of streamflow alteration and biological responses have not been developed on a statewide scale in Minnesota.Best sub-sets regression analysis was used to develop linear regression models that quantify relations among five categories of hydrologic metrics(i.e.,duration,frequency,magnitude,rate-of-change,and timing)computed from streamgage records and six categories of biological metrics(i.e.,composition,habitat,life history,reproductive,tolerance,trophic)computed from fish-community samples,as well as fish-based indices of biotic integrity(FIBI)scores and FIBI scores normalized to an impairment threshold of the corresponding stream class(FIBI_BCG4).Relations between hydrology and fish community responses were examined using three hydrologic datasets that represented periods of record,long-term changes,and short-term changes to flow regimes in streams of Minnesota.Results:Regression models demonstrated significant relations between hydrologic explanatory metrics and fish-based biological response metrics,and the five regression models with the strongest linear relations explained over 70%of the variability in the biological metric using three hydrologic metrics as explanatory variables.Tolerance-based biological metrics demonstrated the strongest linear relations to hydrologic metrics.The most commonly used hydrologic metrics were related to bankfull flows and aspects of flow variability.Conclusions:Final regression models represent paired streamgage records and biological samples throughout the State of Minnesota and encompass differences in stream orders,hydrologic landscape units,and watershed sizes.Presented methods can support evaluations of stream fish communities and facilitate targeted efforts to improve the health of fish communities.Methods also can be applied to locations outside of Minnesota with continuous streamgage data and fish-community samples.