Instream Ecological Flow Research Articles

A copula-based approach to instream ecological flow determination considering inter- and intra-annual runoff variability

ABSTRACT Instream ecological flow (IEF) provides a flow reference value for maintaining the stability of river ecosystems and enriching biodiversity. Existing methods for determining the IEF often consider only one of the intra-annual runoff distribution characteristics or the inter-annual runoff distribution characteristics. In this study, a copula-based ecological runoff determination method is proposed to consider both annual and monthly runoff magnitudes. The marginal distribution functions of annual and monthly runoff are first determined using the maximum likelihood method. Then the copula function is used to construct the joint distribution function of annual and monthly runoff series. Using the flow duration curve method, the IEF under different annual and monthly runoff exceedance probabilities is calculated. The probability values are combined with the initial IEF values to determine the final IEF process. A case study is conducted using real-world data from the Tongtian River in China. The results show that the total annual basic ecological water demands of the Tongtian River in abundant, flat, and dry water years are 138, 102 and 72.2 billion m3. The proposed method effectively avoids the disturbance of extreme runoff.

Evaluation of instream ecological flows based on hydrological alteration in the Upper Huai River, China

Abstract Natural flow regime (instream ecological flow) is a vital element of ecological hydrology, serving a crucial role in the fundamental functions of river ecosystems. Intense human activities, especially reservoir operation, have unavoidably altered the flow regime of the Upper Huai River, leading to further impacts on river ecosystems. It is essential to quantify hydrological alterations in flow regimes and their associated impacts on river ecosystems for effective river water management. Ecological flow indicators, namely ecological deficit and surplus, were analyzed to assess instream ecological flow. The overall degree of alteration (Do) and the Dundee Hydrological Regime Alteration Method (DHRAM) were utilized to evaluate the degree of hydrological alteration. Additionally, the Shannon Index (SI) was employed to estimate the impact of hydrological alterations on ecological diversity in this study. The results reveal that the streamflow series underwent mutation in 1987, leading to a decrease in ecological surplus and an increase in ecological deficit. The overall alteration degree is 32%, with a DHRAM level of 3, signifying low hydrological alteration and moderate ecological risk in the region. Furthermore, the biodiversity of the river has markedly declined due to human activities following the alteration.

Detection and Analysis of the Variation in the Minimum Ecological Instream Flow Requirement in the Chinese Northwestern Inland Arid Region by Using a New Remote Sensing Method

With the development of human society, the balance between the minimum ecological instream flow requirement (MEIFR), which is an essential part of the ecological water demand in arid areas, and anthropogenic water depletion has received increasing attention. However, due to the lack of hydrological station data and river information on arid basins, previous researchers usually considered only the individual ecological water demand of rivers, lakes, or oases. To address this issue, a new method that combines river hydraulic parameters and the wet circumference obtained by an unmanned aerial vehicle (UAV) and remote sensing hydrological station (RSHS) technologies was applied to obtain the MEIFR and, then, systematically and quantitatively explore the balance from the perspective of the entire basin of Aiding Lake from 1990 to 2022, which is the lowest point of Chinese terrestrial territory. The results showed the following: (1) since 1990, the discharge of the seven rivers in the study area increased by 1–6%, and the MEIFR of these rivers increased by 15–100%; both quantities decreased by 3–5% from the upper to the lower reaches of the basin; (2) the surface area and water level of Aiding Lake decreased by 5% and 14%, respectively, but the MEIFR first decreased by 25% from 1990 to 2013 and, then, increased by 66.7% from 2013 to 2022; and (3) from 2011 to 2022, the MEIFR and anthropogenic water depletion exhibited a balance. Against the background of climate change, this research revealed that the MEIFR of the rivers in the Aiding Lake Basin have shown an upward trend over the past 30 years and quantitatively determined the above balance relationship and the period of its occurrence. This study supplied a method that could provide guidance for water resource management by decision-makers at a global level, thus helping achieve the sustainable development goals (SDGs).

Establishment of watershed ecological water requirements framework: A case study of the Lower Yellow River, China

It is of great practical significance to ensure ecological water requirements (EWRs) for the maintenance of river health and the sustainable development of human socioeconomics. How to scientifically determine the comprehensive EWRs and estimate the uncertainty of hydro-ecological tools performed in the process of conducting remains one of the most important yet most complicated issues. In this study, the ecological water requirements framework (EWRsF) of the Lower Yellow River (LYR), which considers instream ecological base flow, survival and reproduction of indicator fish species, equilibrium of erosion and siltation and ecological function of the estuary, was constructed by integrating hydrological, hydraulic and ecological habitat methods. The framework contains three crucial components - determination of instream EWRs and estuarine EWRs, uncertainty analysis of hydro-ecological tools. For instream ecological base flow, we proposed an improved Tennant method, which took into account both seasonality and sediment transport characteristics of the LYR, and could better reflect the actual hydrological regime. For the hydrological ecological response relationship of indicator fish species, we estimated the uncertainty of the model output of River2D to improve its credibility of the simulation results. The results demonstrated that: 1) Two-grade intra-annual monthly EWRs process of suitable and minimum for four instream sections and estuary area were obtained. The flood season (June–October) is the period with the largest proportion of intra-annual instream EWRs, whereas in estuary area, is the spawning period (April–July) of dominant species. 2) The uncertainty of HSI curves directly leads to the uncertainty of model output. Although the shape and position of the WUA curve can be uncertain, it does not affect the judgment of EWRs threshold. 3) The research results can provide scientific basis for water resource management decision-making in the LYR. Additionally, the ideas also have reference significance for similar basins.

Evaluation of instream ecological flow with consideration of ecological responses to hydrological variations in the downstream Hongshui River Basin, China

Due to increasing anthropogenic activities, especially with cascade reservoirs having been constructed, the hydrological regimes of the Hongshui River (HSR) Basin which were mainly shaped by precipitation in the undisturbed period, have inevitably changed, making further impacts on riverine ecological environment. Although previous researches to analyze hydrological alterations of flow regimes are numerous, insightful investigation into ecological impacts behind them is needed for watershed management and riverine ecosystem protection. Employing two generalized eco-flow indicators (ecodeficit, ecosurplus), fluvial biodiversity Shannon Index (SI), and multiple hydrological indicators: Indicators of Hydrologic Alteration (IHA), integrated degree of hydrological variation (D0) and Dundee Hydrological Regime Alteration Method (DHRAM), this study focuses on the evaluation of temporal variations of ecological flow in multiple time scales while considering ecological responses to evolutionary characteristics of flow regimes which were chronologically subject to rainfall and reservoirs-disturbances; in addition, an effective method that combines eco-flow indicators and ecologically-relevant hydrological indicators (ERHIs) to evaluate eco-hydrological regime was proposed. The results indicate that: (1) dam-disturbance has broken the close relationships between ecological flow and precipitation in the near-natural period, causing high level of ecodeficit (0.53 the largest) in flood season and astonishing ecosurplus (1.99 the maximum) in dry season; (2) flow regimes have greatly altered and the degree of integrated hydrological variations reaches 60.22%, with an ecological hazard class at level 3, indicating the riverine ecological environment is at risk of facing moderate damage; (3) contributions of seasonal deficit or surplus of ecological flow have been greatly influenced by reservoirs operations, although with astonishing increment of total seasonal ecosurplus, SI has been abnormally decreasing after 1992 when major reservoir came to operate, indicating the degradation of fluvial biodiversity in the HSR Basin due to dam regulation; (4) the combination of eco-flow indicators and ERHIs, which is capable of mirroring the key hydrological information and related ecological connotation, is prove to be an effective method to evaluate the eco-hydrological regimes. The findings of the study could be instructive to relative researches in other cases and provide scientific guidance for local watershed management.

Nonstationary Ecological Instream Flow and Relevant Causes in the Huai River Basin, China

Based on the daily precipitation data during 1960–2016 at 72 stations and the daily streamflow data during 1956–2016 at 7 hydrological stations in the Huai River Basin (HRB), China, eco-surplus and eco-deficit under influences of abrupt streamflow behaviors were analyzed using Flow Duration Curve (FDC). The relations between indicators of hydrological alteration (IHA) and ecological indicators (Shannon Index, SI) were quantified, investigating impacts of altered hydrological processes on the evaluations of the ecological instream flow. Besides, we also quantified fractional contributions of climatic indices to nonstationary ecological instream flow using the Generalized Additive Models for Location Scale and Shape (GAMLSS) framework. While the possible impact of human activities on ecological instream flow will be revealed based on land use changes data. The results indicated that: (1) FDC is subject to general decrease due to hydrological alterations, and most streamflow components are lower than 25% FDC. We found increased eco-deficit and decreased eco-surplus due to altered hydrological processes. The FDC of the streamflow in the main stream of the HRB is lower than that along the tributaries of the HRB. Eco-surplus (eco-deficit) changes are in good line with precipitation anomaly changes during the Spring, Autumn and Winter periods. However, the hydrological alterations due to hydrological regulations by the reservoirs are the primary cause behind the mismatch between ecological instream flow and precipitation anomalies during summer; (2) Annual and seasonal eco-surplus (eco-deficit) is decreasing (increasing) and that during winter season is an exception. Although higher eco-surplus in winter than in other seasons, the eco-surplus is decreasing persistently and the 21st century witnessed the lowest eco-surplus along the main stream of the HRB. Meanwhile, the Shannon index indicated decreased ecological diversity across the HRB; (3) The ecological instream flow is highly sensitive to The Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO) and Niño 3.4 Sea Surface Temperature Index (Nino3.4). Meanwhile, the ecological instream flow along the mainstream of the HRB is highly sensitive to climate indices. While the ecological instream flow by GAMLSS model has better fitting performance in describing the extreme values and local trends.

Calculation of the instream ecological flow of Shifengxi River in Zhejiang Province, China using hydrology and section morphology analysis method

The instream ecological flow is one of the most important obligatory targets of water resources development and utilization, as it is the premise and basis for sustainable water resources development and water ecological environment protection. This paper proposed an instream ecological flow calculation method based on hydrology and section morphology analysis. The method had a certain concept of guarantee rate, and also considered the hydrological habitat requirements of the river section. The application of the method in Shifengxi river basin located in Taizhou city shows that the instream ecological flow of the Shaduan section is 14.0 m3/s during the spawning period and 3.1 m3/s during the normal period.

Calculation of Comprehensive Ecological Flow with Weighted Multiple Methods Considering Hydrological Alteration

Instream ecological flow is an essential determinant of river health. Intra- and interannual distribution characteristics of runoff have been altered to different degrees by dam construction. Historical runoff series with alterations, as basic data for ecological flow calculation, provide minimal instream hydrological process information, which affects the credibility of calculation results. Considering the influence of the alterations in runoff series on ecological flow calculation, the Gini coefficient (GI) is introduced to study the evenness degrees of the intra-annual runoff distribution of four hydrological stations located in the Naolihe basin of the Sanjiang Plain. The hydrological alteration diagnosis system is used to examine the alteration points in the GI series of each hydrological station for selecting reasonable subsequences. Based on the selected subsequences, the ecological flow of each station is calculated using three hydrological methods, and the comprehensive ecological flow is calculated using weighted calculation results from the three hydrological methods. The study results show that ecological flow and natural flow have similar processes with two peaks occurring in the process in May and August, respectively. Also, dams decrease the ecological water requirement damage frequency in dry seasons, but overuse of water resources increases the ecological water requirement damage frequency in flood seasons.

Ecohydrological effects of water reservoirs with consideration of asynchronous and synchronous concurrences of high- and low-flow regimes

ABSTRACTInflow of nine reservoirs in the Liao River basin, China, is used to analyse the concurrence of high/low flows, and also the ecological instream flow. The results indicate that the general extreme value distribution model performs well in describing the probabilistic behaviour of high/low flows in the basin. Specifically, the Gumbel and Frank copula functions perform better than other functions. Reservoir inflow encounter series are subject to high synchronous concurrence, at greater than 27% for low flow vs low flow. Thus, the water supply system of the basin is not steady. The ecological instream flow can be analysed by a monthly frequency computation method, with 90% guarantee rate. The low-flow periods are January, February and May, and water transfers are not feasible in these periods. Thus, external sources of water are urgently needed to guarantee sufficient water supply to provide critical water resources and to protect important aquatic environments.

Instream ecological flow and reservoir ecological operation in the upper reaches of Irtysh River

Instream ecological flow (IEF) and flow-related variations were important for healthy river systems. However, water conservancy projects such as reservoirs altered the processes of IEF and thereby posed considerable threat to the health of river systems and aquatic lives. To that end, in this study the effects of reservoir construction on IEF in the upper reaches of the Irtysh River were analyzed using an improved hydrological method. The computed results were in turn used to determine the maximum (MaxIEF), minimum (MinIEF) and optimal (OptIEF) instream ecological flows of the river. Based on the study, reservoir impoundments limited IEF in wet seasons but enhanced it in dry seasons. It also narrowed suitable flow range for reproduction and growth of aquatic life. Reservoirs could be used to regulate Irtysh River discharge. For healthy instream processes in wet years, OptIEF could be set as the lower limit and MaxIEF as the upper limit. For much the same reasons, MinIEF could be set as the lower limit in dry years and OptIEF as a suitable target in normal years.

Evaluation of ecological instream flow considering hydrological alterations in the Yellow River basin, China

Abstract The Yellow River is the second largest river in China and is the important source for water supply in the northwestern and northern China. It is often regarded as the mother river of China. Owing to climatic change and intensifying human activities, such as increasing withdrawal of water for meeting growing agricultural irrigation needs since 1986, the flow of Yellow River has decreased, with serious impacts on the ecological environment. Using multiple hydrological indicators and Flow Duration Curve (DFC)-based ecodeficit and ecosurplus, this study investigates the impact of hydrological alterations, such as the impact of water reservoirs or dams, on downstream ecological instream flow. Results indicate that: (1) due to the impoundment and hydrological regulations of water reservoirs, occurrence rates and magnitudes of high flow regimes have decreased and the decrease is also found in the magnitudes of low flow events. These changes tend to be more evident from the upper to the lower Yellow River basin; (2) human activities tend to enhance the instream flow variability, particularly after the 1980s;(3) the ecological environment in different parts of the Yellow River basin is under different degrees of ecological risk. In general, lower to higher ecological risk can be detected due to hydrological alterations from the upper to the lower Yellow River basin. This shows that conservation of ecological environment and river health is facing a serious challenge in the lower Yellow River basin; (4) ecological instream flow indices, such as ecodeficit and ecosurplus, and IHA32 hydrological indicators are in strong relationships, suggesting that ecodeficit and ecosurplus can be regarded as appropriate ecological indicators for developing measures for mitigating the adverse impact of human activities on the conservation of ecological environment in the Yellow River basin.

Assessment of ecological instream flow requirements under climate change Pseudorasbora parva

Climate change alters ecohydrological processes on different temporal and spatial scales. The aim of this study was to estimate ecological instream flow requirements (EIFR) under climate change impacts and to ascertain optimum flow magnitude to maintain the health of river ecosystems. We used the Mann–Kendall test, the River2D Hydrodynamic model, and the frequency-weighted usable area (FWUA) model on an annual scale in the Juma River to investigate changes in EIFRs caused by climate change. Findings indicated that: (1) between 1956 and 2005, annual instream flow in the Juma River exhibited an abrupt downward trend (in 1981); (2) variation in instream flow governed the area of available fish habitat, and degrees of change for low flow threshold values and low and high FWUA threshold almost exclusively occurred in descending sequential order from winter, spring, autumn, and summer; (3) changes in hydrological regimes influenced both the quantity and quality of physical habitat area, contributing greater to quality than to the distribution of area of physical habitat for Pseudorasbora parva. Climate change, reflected in the changes in EIFR and the area of optimum physical habitat, has dramatically influenced ecological structure and function, even in the small river system investigated for this study. Findings indicated that more rational measures should be put into practice to help address climate change.

Estimating shallow groundwater availability in small catchments using streamflow recession and instream flow requirements of rivers in South Africa

Groundwater is an important resource for multiple uses in South Africa. Hence, setting limits to its sustainable abstraction while assuring basic human needs is required. Due to prevalent data scarcity related to groundwater replenishment, which is the traditional basis for estimating groundwater availability, the present article presents a novel method for determining allocatable groundwater in quaternary (fourth-order) catchments through information on streamflow. Using established methodologies for assessing baseflow, recession flow, and instream ecological flow requirement, the methodology develops a combined stepwise methodology to determine annual available groundwater storage volume using linear reservoir theory, essentially linking low flows proportionally to upstream groundwater storages. The approach was trialled for twenty-one perennial and relatively undisturbed catchments with long-term and reliable streamflow records. Using the Desktop Reserve Model, instream flow requirements necessary to meet the present ecological state of the streams were determined, and baseflows in excess of these flows were converted into a conservative estimates of allocatable groundwater storages on an annual basis. Results show that groundwater development potential exists in fourteen of the catchments, with upper limits to allocatable groundwater volumes (including present uses) ranging from 0.02 to 3.54×106m3a−1 (0.10–11.83mma−1) per catchment. With a secured availability of these volume 75% of the years, variability between years is assumed to be manageable. A significant (R2=0.88) correlation between baseflow index and the drainage time scale for the catchments underscores the physical basis of the methodology and also enables the reduction of the procedure by one step, omitting recession flow analysis. The method serves as an important complementary tool for the assessment of the groundwater part of the Reserve and the Groundwater Resource Directed Measures in South Africa and could be adapted and applied elsewhere.

Evaluation of ecological instream flow using multiple ecological indicators with consideration of hydrological alterations

Dam-induced hydrological alterations and related ecological problems have been arousing considerable concern from hydrologists, ecologists, and policy-makers. The East River basin in China is the major provider of water resources for mega-cities within the Pearl River Delta and meets 80% of annual water demand of Hong Kong. In this study, ecodeficit and ecosurplus were analyzed to determine the ecological impact of water impoundments. Also, Do and DHRAM were employed to evaluate the degree of alteration of hydrological regimes, and ERHIs were analyzed to evaluate the influence of hydrological alterations on ecological diversity. Results indicate that: (1) the magnitude and frequency of high flows decrease and those of low flows increase due to the regulation of reservoirs; (2) variations of annual ecosurplus are mainly the result of precipitation changes and the annual ecodeficit is significantly influenced by reservoirs. However, ecodeficit and ecosurplus in other seasons, particularly autumn and winter, are more influenced by reservoir regulation; (3) impacts of reservoirs on hydrological regimes and eco-flow regimes are different from one station to another due to different degrees of influence of reservoirs on hydrological processes at different stations. The longer the distance between a reservoir and a hydrological station is, the weaker the influence the water reservoir has on the hydrological processes; (4) ecodeficit and ecosurplus can be accepted in the evaluation of alterations of hydrological processes at annual and seasonal time scales. Results of Shannon Index indicate decreasing biological diversity after the construction of water reservoirs, implying negative impacts of water reservoirs on biological diversity of a river basin and this should arouse considerable human concerns. This study provides a theoretical background for water resources management with consideration of eco-flow variations due to reservoir regulation in other highly-regulated river basins of the globe.

水文变异条件下鄱阳湖流域生态流量研究

PDF HTML阅读 XML下载 导出引用 引用提醒 水文变异条件下鄱阳湖流域的生态流量 DOI: 10.5846/stxb201404080664 作者: 作者单位: 中山大学 水资源与环境系,江西师范大学 鄱阳湖湿地与流域研究教育部重点实验室,中山大学 水资源与环境系,中山大学 水资源与环境系,中山大学 水资源与环境系 作者简介: 通讯作者: 中图分类号: 基金项目: 鄱阳湖湿地与流域研究教育部重点实验室(江西师范大学)主任开放基金资助项目(ZK2013006); 安徽省高校引进"领军人才"专项项目 Evaluation of ecological flow with considerations of hydrological alterations in the Poyang Lake basin Author: Affiliation: Department of Water Resources and Environment,Sun Yat-sen University,Department of Water Resources and Environment,Sun Yat-sen University,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:受气候变化和人类活动综合影响,鄱阳湖流域水文状况发生变异。河流生态系统适应了变异前的水文状况,变异后势必会影响当地生态系统。基于此,采用8种变异检测方法对水文变异进行综合诊断,阐明水文变异原因。在此基础上,采用15种概率分布函数分别拟合5站各月变异前日流量序列,最终确定5站点各月最优分布函数及所对应的概率密度最大处的流量,即得河道内生态流量。研究表明:(1)抚河于1962年发生弱变异,赣江、修河于1968年发生中变异,信江、饶河于1991年发生弱变异;(2)变异后,赣江、信江、饶河、修河生态需水满足率平均上升11%,抚河生态需水满足率下降32%;(3)水文变异增加提高生态需水满足率,水利工程建设降低年均生态需水满足率、提高干季生态需水满足率。高森林覆盖率提高干季生态需水满足率,对年均生态需水满足率影响不明显。研究结果为鄱阳湖流域水资源管理及区域水资源规划与配置提供重要科学依据。 Abstract:Fluvial hydrological processes within the Poyang Lake basin are significantly altered under the influence of human activities and climate changes. Poyang Lake is the largest freshwater lake and plays an important role in conservation of biological diversity and also in flood mitigation in the Yangtze River basin. In this case, ecological instream streamflow is also altered and the ecological environment is potentially affected under the influences of altered hydrological processes. With consideration of hydrological alterations, re-evaluation of ecological instream streamflow will be of great scientific and practical merit in terms of water resource management and conservation of ecological environment. We use the Hurst coefficient method to preliminary analyze the degree of alterations in five major tributaries of the Poyang lake basin. Then we use eight mutation testing methods to comprehensively investigate change points. We use 15 kinds of probability distribution functions to fit respectively daily flow for each month before occurrence of the hydrological alterations. Finally, the monthly optimal distribution functions and corresponding streamflow with the largest probability are determined and computed, and accepted as the ecological instream streamflow. Results indicate that: (1) main causes behind the hydrological alterations of the Gan, Xin, Rao and Xiu Rivers are the climate changes such as the precipitation changes observed in this study. However, the Hu River is mainly affected by human activities; (2) due to large amounts of water diversion irrigation system, hydrological processes in the Hu River were significantly altered after 1962. The hydrological alterations of the Gan and Xiu Rivers occurred in 1968. The East Asian Summer Monsoon led to anincrease of precipitation during the mid-1960s; The Xin, Rao Rivers were dominated by significant hydrological alterations in 1991. Increase of precipitation in the early 1990s is the main cause behind this hydrological alterations that occurred in the 1960s;(3) The increase of forest coverage and the construction of water conservancy are expected to improve the satisfaction rate of the ecological water requirement in the dry season. The satisfactory rate of ecological water requirement in the dry season is higher than that in the wet season in the Rao, Gan, and Xiu Rivers. However, the Fu and Xin Rivers do not follow this trend. The forestation and increased vegetation coverage can greatly alter the spatiotemporal distribution of water or runoff and can significantly increase the runoff during the dry seasons. Woodland has an important influence on the changes of runoff. Due to the large forest coverage, the ecological instream flow is greatly satisfied during dry seasons in the Rao River when compared to the other four rivers. A difference is found in the Gan River in terms of water requirements of ecological instream flow between wet and dry seasons. The number of reservoirs in the Gan River basin is high when compared to the other four tributaries of the Poyang Lake basin that were considered in this study. Forest coverage in the Xiu River basin accounts for 64.4% of the total area, which is ranked the second largest in the Poyang Lake. However, the difference between wet and dry seasons is small. The quantity and scale of the reservoir in the Xiu River basin falls far behind others. Therefore, the regulation activities of the reservoirs in Xiu River basin is not evident than other river basins. On the contrary, the satisfactory rate of ecological water requirements for the dry season is below that for the wet season in the Fu and Gan River. The rate of forest coverage in those two basins is far less than in other basins. The ability to regulate the forest is limited. These results will provide an important scientific basis for the planning and management of water resources within the Poyang Lake basin under a changing environment. 参考文献 相似文献 引证文献

Calculation of the Instream Ecological Flow of the Wei River Based on Hydrological Variation

It is of great significance for the watershed management department to reasonably allocate water resources and ensure the sustainable development of river ecosystems. The greatly important issue is to accurately calculate instream ecological flow. In order to precisely compute instream ecological flow, flow variation is taken into account in this study. Moreover, the heuristic segmentation algorithm that is suitable to detect the mutation points of flow series is employed to identify the change points. Besides, based on the law of tolerance and ecological adaptation theory, the maximum instream ecological flow is calculated, which is the highest frequency of the monthly flow based on the GEV distribution and very suitable for healthy development of the river ecosystems. Furthermore, in order to guarantee the sustainable development of river ecosystems under some bad circumstances, minimum instream ecological flow is calculated by a modified Tennant method which is improved by replacing the average flow with the highest frequency of flow. Since the modified Tennant method is more suitable to reflect the law of flow, it has physical significance, and the calculation results are more reasonable.

A time‐series model for assessing instantaneous physical conditions in carp habitats

ABSTRACTThe four main Chinese carps, collectively abbreviated as MCHA, include the black carp (Mylopharyngodon piceus), grass carp (Ctenop haryngodon idellus), silver carp (Hypoph thal michthys molitrix), and the big‐head carp (Aristichyths nobilis). MCHA constitutes a significant catch of China's fresh water fishery. The construction of the Gezhouba and Three Gorges Dams greatly affects the physical habitat conditions of these four main carp species. This paper presents a time‐series model for the assessment of instantaneous physical conditions in MCHA habitats. The model incorporates the effects of various hydrological variables (e.g. water level fluctuation, water temperature and sediment concentration) on MCHA habitat quality. The model is tested for the Yichang‐Zhijiang reaches of the Yangtze River – a suitable region for analysing the effects of dam construction on the physical conditions of MCHA habitat. The model analyses instream ecological flow (IEF) characteristics of the study area in the spawning season of MCHA. On the basis of the analysis, the min, max and optimal IEFs are 6200, 51000 and 14 500 m3/s, respectively. The model introduces an efficient method for calculating the instantaneous habitat area on the basis of IEF and other physical conditions. If properly applied, the model is an efficient tool for assessing the effects of variations in flow conditions on MCHA habitat quality. The model could also be used in real time to analyse the combined effect of ecological regulations (e.g. as induced by the Three Gorges and Gezhouba Dams) on MCHA spawning conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Eco-Hydrological Requirements in Arid and Semiarid Regions: Case Study of the Yellow River in China

AbstractThe eco-hydrological requirements of a river are related to the health of the river. In recent years, changing climate and intensifying human activities have further aggravated water problems in the Yellow River. Considering hydrological changes, this study addressed the ecological water requirements of the Yellow River basin, wherein the threshold ecological water requirement corresponded to the streamflow with the largest occurrence probability determined by the Pearson Type III distribution. Instream flow ± one standard deviation was adopted as the water resource management target and abrupt changes in streamflow were detected by using the Mann-Whitney U test. The results of the analysis indicated that: (1) the annual flow of the Yellow River substantially decreased after abrupt changes and the probability significantly dropped that the amount of annual streamflow satisfied the ecological instream flow requirement; and (2) the water resource management target was satisfied well after th echange...

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

Abstract: Yongding River, as the mother river of Beijing city, has been dried up from Sanjia Dian since 1980s. The naked riverbed and the desertification of its both sides play a main role of sandy weather in spring of Beijing. The Quaternary period underground water of the west Beijing has been drained off, because of the overload of the underground water plus with no supply pouring into. The ecological system of Yongding River has severely been devastated. If we want Yongding River to be recovered, we should clarify the quantity of the most active and the most important water. This paper calculated the instream ecological flow in three monitored sections of Yongding River Guanting Reservoir with wetted perimeter method. The three sections are Guanting Reservoir (under dam), Yanchi and Lugou Bridge. Respectively, the flows in the instream of each section are 3.7 m3 s-1 (the normal flow year, P=50%, 1978) accounting for 20.7% of the average annual flow, 4.1 m3 s-1(the normal flow year, P=50%, 1981) accoun...

Calculation and Analysis of the Instream Ecological Flow for the Irtysh River

Instream ecological flow is essential determinant of river health. In this paper, the monthly minimum flow calculation method, the (new) monthly frequency calculation method were applied to calculate and evaluate the minimum instream ecological flow and the optimal instream ecological flow for the Irtysh River, and the different criteria of instream ecological flow was calculated by the improved Tennant method. It is expected to provide a scientific basis for the reasonable allocation of water resource in Irtysh River basin by calculating the instream ecological flow.