Environmental Flows In Rivers Research Articles

Working (around/within/against) prior appropriation: Diverse hydrosocial practices to secure water for rivers

Water scarcity in the Western US, through the lens of political ecology, can be understood as inextricably shaped by power dynamics, governance structures, and legal practices of resource allocation. Water allocation in the region is determined largely by the legal doctrine of Prior Appropriation, the 'first in time, first in right' principle. However, prior appropriation is fundamentally based in anthropocentric and settler colonial assumptions, and in light of drought, climate change, and shifting social and environmental values, the system has been critiqued as inadequate to meet contemporary water challenges. Despite challenging historical legacies, water managers in the Western US are developing a range of strategies to work around or within prior appropriation to secure environmental flows for rivers and aquatic species. In this article we use political ecology and diverse economies approaches to consider the challenges of, and challenges to, prior appropriation. We examine a diverse set of practices, work-arounds, and creative strategies being used to secure instream flows, and discuss how these strategies affirm or challenge prior appropriation, how they reinforce or challenge inequities, and how they reform or re-envision water allocation in ways that may open up potential for social and environmental justice.

Effect of dam construction on changes in river's environmental flow (case study: Gorganrood river in the south of the Caspian Sea)

Human activities such as dam construction can lead to significant river flow regime changes and, consequently, river environments and habitats. Different approaches for estimating the environmental flow have developed to improve the river ecosystem's environmental and habitat conditions. The hydrological approach is considered in many studies to estimate environmental flows considering its advantages. Vimba vimba persa is an economically and ecologically valuable species in the Caspian Sea that spawns and reproduces naturally in the Gorganrood River downstream in April–May. After the construction of the Voshmgir dam on the Gorganrood River, the fish population has drastically reduced in recent decades. In this study, to investigate the effect of constructing the Voshmgir dam on the environmental flow of Gorganrood River, a wide range of hydrological methods, including Tennant, Tessman, Arkansas, Aquatic Base Flow, Flow Duration Curve, High Flow-Low Flow, and FDC Shifting have been used. Comparing the correlation between the mean monthly flow time series before and after the Voshmgir dam demonstrates remarkable changes, including Pearson (0.95 to 0.86), Spearman's rho (0.93 to 0.78), and Kendall's τ (0.78 to 0.61) as a consequence of dam construction. The results indicate that estimated environmental flow from Tennant (1.1, 3.4 to 1.3, 3.8 cms) and Aquatic Base Flow (0.5 to 1.8 cms) methods have led to inadequate estimation due to significant changes in flow in different months. The amount of environmental flow during April–May estimated from investigated methods indicates the dam negatively affected water allocation to meet the river downstream's ecological and environmental needs. The flow duration curve analysis confirms that the dam construction has caused the river flow to fluctuate significantly within the year. The dam construction has dramatically reduced the flow in April–May, a critical environmental and ecological season. The April–May period coincides with the river's flood season. The construction of the Voshmgir dam has caused the components of high flow in the environmental flow to face severe shortages.

Quantifying Environmental Flow in the Form of Pulse Flow for Fish Protection

Pulse flow, which includes base flow, peak flow, flow duration, occurrence time, and frequency, is a manifestation of environmental flow in rivers. This paper describes a methodological framework for determining pulse flow based on an analysis of fish spawning behavior and presents its application to the second Songhua River in northeastern China. Peak flow was determined based on the hydrographic-habitat relationship for fish spawning in conjunction with physical habitat simulation. The flow duration was determined based on the incubation period of fish eggs. The occurrence time and frequency were determined based on the suitable temperature for fish spawning. This application differs from conventional methods for dividing fish spawning periods and selecting target species in the corresponding period. Fish were divided into cold-water fish, hypothermal-water fish, and warm-water fish according to spawning temperature, and the target species in each month of the spawning period (April to July) were identified. For the same spawning period, the hydrographic-habitat relationships of target species with adhesive and drifting eggs were weighted to determine the peak flow. The most suitable peak flow for fish spawning from April to May in the research region is 900 m3/s and 1200 m3/s for June to July. Using the proposed framework, an ecological hydrograph from April to July was obtained by combining the method of pulse flow with habitat simulation. Fifteen days, eight days, and five days were chosen as the flow durations for April, May, and June to July, respectively. We recommend scheduling two high pulse flows each month from May to July while limiting the occurrence to only one in April. The results show that this framework offers a promising approach for developing environmental flows in rivers with a variety of fish species.

Research on the improvement of wetted perimeter method and application in seasonal rivers-a case study of Fenhe River, China.

Environmental flow is vital for maintaining river ecosystem health and ensuring the normal growth of aquatic organisms. The wetted perimeter method is indeed very useful in the assessment of environmental flow due to consideration of stream forms and minimum flow for aquatic life habitat. In this study, a river with obvious seasonality and external water diversion was selected as the typical research object; taking Jingle, Lancun, Fenhe Reservoir, and Yitang hydrological sections as control sections, we improved the existing wetted perimeter method in three aspects: (1) We improved the selection of hydrological data series. The selected hydrological data series should be of a certain length and can well reflect the hydrological changes of wet, normal, and dry years. (2) Different from the traditional wetted perimeter method, which only gives one environmental flow value, the improved method calculates the environmental flow month by month. (3) The improved wetted perimeter method establishes the relationship between native fish survival and environmental flow. Results indicated that the improved wetted perimeter took the survival of the main fishes into consideration, the ratio of the calculated results by the slope method to the multi year average flow was greater than 10%, which can ensure the fishes' habitat is not being destroyed, and the results are more reasonable. Furthermore, the monthly environmental flow processes obtained were better than the annual unified environmental flow value determined by the existing method and are consistent with the natural hydrological situation and water diversion situation of the river. This study shows that the improved wetted perimeter method is feasible for research of river environmental flow with strong seasonal and large variation of annual flow.

An integrated simulation–optimization framework for assessing environmental flows in rivers

The present study proposes an integrated simulation–optimization framework to assess environmental flow by mitigating environmental impacts on the surface and ground water resources. The model satisfies water demand using surface water resources (rivers) and ground water resources (wells). The outputs of the ecological simulation blocks of river ecosystem and the ground water level simulation were utilized in a multiobjective optimization model in which six objectives were considered in the optimization model including (1) minimizing losses of water supply (2) minimizing physical fish habitat losses simulated by fuzzy approach (3) minimizing spawning habitat losses (4) minimizing ground water level deterioration simulated by adaptive neuro fuzzy inference system(ANFIS) (5) maximizing macroinvertebrates population simulated by ANFIS (6) minimizing physical macrophytes habitat losses. Based on the results in the case study, ANFIS-based model is robust for simulating key factors such as water quality and macroinvertebrate’s population. The results demonstrate the reliability and robustness of the proposed method to balance environmental requirements and water supply. The optimization model increased the percentage of environmental flow in the drought years considerably. It supplies 69% of water demand in normal years, while the environmental impacts on the river ecosystem are minimized. The proposed model balances the portion of using surface water and ground water in water supply considering environmental impacts on both sources. Using the proposed method is recommendable for optimal environmental management of surface water and ground water in river basin scale.

Automated environmental compliance monitoring of rivers with IoT and open government data

Environmental monitoring of rivers is a cornerstone of the European Union's Water Framework Directive. It requires the estimation and reporting of environmental flows in rivers whose characteristics vary widely across the EU member states. This variability has resulted in a fragmentation of estimation and reporting methods for environmental flows and is exhibited by the myriad of regulatory guidelines and estimation procedures. To standardise and systematically evaluate environmental flows at the pan-European scale, we propose to formalise the estimation procedures through automation by reusing existing river monitoring resources. In this work, we explore how sensor-generated hydrological open government data can be repurposed to automate the estimation and monitoring of river environmental flows. In contrast to existing environmental flows estimation methods, we propose a scalable IoT-based architecture and implement its cloud-layer web service. The major contribution of this work is the demonstration of an automated environmental flows system based on open river monitoring data routinely collected by national authorities. Moreover, the proposed system adds value to existing environmental monitoring data, reduces development and operational costs, facilitates streamlining of environmental compliance and allows for any authority with similar data to reuse or scale it with new data and methods. We critically discuss the opportunities and challenges associated with open government data, including its quality. Finally, we demonstrate the proposed system using the Estonian national river monitoring network and define further research directions.

Ecological status estimation for the Kalaus river in the Stavropolskii region

The Kalausis the river in the Stavropolskii region of Russia being an important source of water. Water use has caused water decrease, water depletion and water deterioration. Therefore water shortages exceed natural river flow by 100%. The water quality category is estimated as “very dirty”. The main source of river water pollution is diffuse runoff from agricultural lands. Estimationson both the environmental river flow and the efficiency of water protection measures are given in this paper. It considers the impact of the lands on the flow volume and quality of the river water, and also estimates the impact of global climate change on water scarcity. To improve the ecological status of the river up to “satisfactory” it is necessary to save the volume of environmentally friendly flow without its with drawing. To improve the water quality up to “moderately polluted” it is necessary integrated water protection measures.

Assessment and Implementation of Environmental Flows to Restore River Gomti- a Tributary of Ganga, India

Environmental flows in rivers are essential to maintain their natural regime, purify themselves, sustain aquatic life and vegetation, recharge groundwater and support livelihoods. Rivers play their role in people’s cultural and spiritual lives. These functions are possible with a suitable e-flow regime. This paper aims to quantify E-Flows for alluvial river Gomti- a tributary of river Ganga, at upstream and downstream of Lucknow City, at Sultanpur and at Jaunpur. These E-flow sites were chosen on the basis of homozonation study of Gomti Basin. Two methodsHydrological consideration and holistic approach: Building Block Methodology has been employed for assessing the Eflows at four sites falling in middle and lower zone of the Gomti Basin. The two set of E-Flows obtained have been compared with observed flows and virgin flows limits to visualize the implications of implementation plan for normal maintenance year and drought year. Considering Gomti basin water plan for 2045 while trying to meet future sectoral water demand and managing e-flows minimum allocation, the paper argues for e-flows implementation by participatory wetland conservation and improvise agricultural water use efficiency. Summary of investment plan in Gomti Basin to manage demand and supply of water optimally including minimum e-flows in Gomti river. Freed water from agriculture may be diverted into river Gomti from irrigation canal systems, offtaking from Sharda and Ghaghara rivers passing through the Gomti basin. It is found that recommended monthly E-flows for Mehndighat is higher than the observed flows and even more than virgin flow volume except in the month of July. At Fuslauna site E-flows are higher than estimated virgin and observed flow for the months of January to June and for rest of the months July to December, E-flows values are within virgin/observed flow volume limits. Hence to implement Eflows in Gomti river at Fusluana site, additional water from Sharda Sahayak Feeder, through Gomti escape has to be released for lean flow months January to June. Augmentation of flows in Gomti river is recommended by increasing base flows contribution particularly during lean flow months. For Sultanpur and Jaunpur sites required e-flows are almost twice higher than the present day flows in Gomti river. E-flows for Gomti river at Jaunpur is higher than the virgin flow for the month of January to June, estimated at Maighat - a d/s CWC site below Jaunpur. Alternatively, based on MOWR guidelines (as issued in case of Ganga river) considering only hydraulic perspective, minimum E-Flows for Gomti river at Lucknow, Sultanpur, Jaunpur and Maighat has been calculated. E-Flow estimates for Lucknow comes to 15.02 m3 /s, 7.70 m3 /s and 3.41m3 /s during monsoon (June to Sep.), non lean flow month (Oct & Nov.) and lean flow months Dec to May respectively. For Sultanpur site 42.70 m3 /s, 23.73 m3 /s and 10.26m3 /s and for Jaunpur site 44.94 m3 /s, 29.22 m3 /s and 11.28m3 /s has been obtained for the same period. E-flows assessed applying BBM, monthly discharge ranges are for Mehndighat 40-415 m3 /s, Aqueduct site 40-58 m3 /s, Sultanpur 92-950 m3 /s and for Jaunpur site 100-795 m3 /s. During wet months flushing requirement for two weeks period is 310 m3 /s at Lucknow, 1370 m3 /s at Sultanpur and 2450 m3 /s for Jaunpur. This peak flow appears possible at Lucknow due to barrage but difficult to implement at Sultanpur and Jaunpur . Although ever maximum discharge observed had been at Lucknow 916.97m3 /s, at Sultanpur 1373.68 m3 /s at Jaunpur 2991.82 m3 /s and at Maighat 3521.53 m 3 /s but on average and 75% dependability level these flow becomes very low. It is suggested that E-Flows assessed for Gomti river using BBM may be refined on the basis of more research carried out with informed hydrology, biodiversity habitat conditions and parameters of geomorphology.

Fulfillment of river environmental flow: applying Nash theory for quantitative‐qualitative conflict resolution in reservoir operation

AbstractThe construction of reservoirs for water supply alters the riverine ecology and changes water quality. It is, therefore, imperative to estimate and provide the riverine environmental flow requirement to prevent irreversible environmental damage and to maintain suitable water quality. Water releases from reservoirs constitute the means for meeting environmental flow and water quality requirements downstream from reservoirs. These requirements can be realized through the modification of the reservoir operation programmes by reallocating a percentage of the reservoir releases otherwise dedicated to quantitative objectives. This is performed in this study by considering the qualitative (i.e. pertaining to water quality) objectives alongside quantitative objectives of reservoir releases in order to achieve a general coverage for an operating programme that balances in the most rational manner the interests of riverine environmental protection and quantitative functions. The case study area is located in the river reach between the Gotvand reservoir and Shooshtar city in the Gotvand‐Karoon reservoir‐river system in Iran. The range of riverine environmental flow is calculated in the study river reach with hydrologic methods. Water quality is simulated and included reservoir operation with the QUAL‐2K simulation model. The existing quantitative and qualitative objectives for reservoir operation are determined and classified. The best reservoir releases corresponding to three scenarios are determined by the Nash theory considering all possible objectives in the reservoir‐river system. These scenarios allocate relative weights to defined objectives and releases were determined to be equal to 183.8, 141.8 and 206.8 m3/s for three scenarios.

Assessment of dam appurtenant structures under multiple flow discharge scenarios

This study investigates the capacities of chute spillway and stilling basin under multiple flow discharge scenarios. Thirteen cases, categorised as low, medium, and high flow discharges were experimentally conducted, with a 100% increase of Probable Maximum Flood (PMF) as the modified maximum flow. An analysis is extended to flood and scour potential at the Type II and III stilling basin. Low and medium discharge scenarios have no significant impact on the spillway but posed insufficient capacity to confine efficiently the hydraulic jump within the stilling basin. Types II and III basins reduced the length of hydraulic jump up to 50% and 73%, respectively at PMF. Similarly, potential of severe scour particularly at the spillway exit increases to 5 times more than the cases for low discharge. Similarly, potential of severe scour at PMF, particularly at the spillway exit increases to 5 times more than the cases for low discharge. High discharge not only compromises the spillway integrity due to overflow but also increases flood and scour potential at the stilling basin. An up-to-date evaluation of the existing dam appurtenances capacities to withstand the future flow pattern is crucial to ensure smooth dam operations and avoiding catastrophic events such as dam breach, jeopardising the river environmental flow and water resources.

Determination of Environmental Flows for the Barbuda Stream in the Municipality of Olaya, Antioquia, Colombia

Environmental flow determination is important for the management of rivers and reservoirs. This parameter allows us to calculate the water supply of basins and minimize environmental impacts associated with water harvesting. In the past, research has been performed to determine environmental flows in rivers of Antioquia. However, the results did not include annual weather variation. Mean environmental flows, evapotranspiration and infiltration in the area have been calculated with the rainfall data registered in the Olaya station during 20 years and the basin morphometric parameters. The collected data were used to build a mathematical model in MATLAB and determine the environmental flows with the Range of Variability Approach (RVA) method for each month of the year and ENSO periods. The model can be used to determine environmental flows in similar basins using new rainfall data and morphometric parameters.

A Perspective on Training Methods Aimed at Building Local Capacity for the Assessment and Implementation of Environmental Flows in Rivers

This paper describes the development and delivery of a global training programme for environmental flows in rivers. The programme was developed in South Africa, and formalised with WWF. It has been delivered at various levels of detail, to specialist teams of scientists and managers (as learning-by-doing), and to large numbers of post-graduate students, in more than 20 countries worldwide. The intention has been to build local capacity and initiate E flows implementation. The general format of the training is described, and a number of examples and case studies are used to demonstrate the successes and pitfalls of the process. The examples concentrate on the need for long-term commitment and persistence in the face of multiple impediments, chief among them the need to change mind-sets of water policy makers, managers, scientists, and all levels of stakeholders, who traditionally view rivers as resources to be used to the maximum extent, rather than as valuable assets to be protected. They also illustrate examples of misunderstanding and resistance to implementing E flows. Lessons from training and implementation over 25 years include: • The need for local champions, with a long-term commitment • The need for understanding and support from all levels of stakeholders • The need (at least initially) to simplify the process as much as possible, so as to foster understanding and support, and to demonstrate successes within a time frame that maintains that support.

Determination of environmental flows in rivers using an integrated hydrological-hydrodynamic-habitat modelling approach

We propose the novel integrated modelling procedure 3H-EMC for the determination of the environmental flow in rivers and streams; 3H-EMC combines Hydrological, Hydrodynamic and Habitat modelling with the use of the Environmental Management Classes (EMCs) that are defined by the Global Environmental Flow Calculator. We apply 3H-EMC in the Sperchios River in Central Greece, in which water abstractions for irrigation cause significant environmental impacts. Calculations of the hydrodynamic-habitat model, in which the large and the small chub are the main fish species, suggest discharge values that range from 1.0 m3/s to 4.0 m3/s. However, hydrological modelling indicates that it is practically difficult to achieve discharges that are higher than approximately 1.0–1.5 m3/s. Furthermore, legislation suggests significantly lower values (0.4–0.5 m3/s) that are unacceptable from the ecological point of view. This behaviour shows that a non-integrated approach, which is based only on hydrodynamic-habitat modelling does not necessarily result in realistic environmental flows, and thus an integrated approach is required. We propose the value of 1.0 m3/s as the “optimum” environmental flow for Sperchios River, because (a) it satisfies the habitat requirements, as expressed by the values of weighted useable area that are equal to 2180 and 1964 m2 for the large and small chub, respectively, and correspond to 82 and 95% of their respective maximum values, (b) it is consistent with the requirements of Environmental Classes A and B, whose percentiles are higher than 75% for discharge (77.2%) and for habitat availability (>83.5% for the large chub and >85.0% for the small chub), (c) it is practically achievable from the hydrological point of view, and (d) it is higher than the value proposed by the Greek legislation. The proposed modelling approach can be applied to any river or stream using the same or similar modelling tools, which should be linked via suitable coupling algorithms.

How much groundwater can we pump and protect environmental flows through time? Presumptive standards for conjunctive management of aquifers and rivers

AbstractGroundwater is a critically important source of water for river, wetland, lake, and terrestrial ecosystems, yet most frameworks for assessing environmental flows have ignored or not explicitly included the potential impacts of groundwater pumping on environmental flows. After assessing the processes and existing policies for protecting streamflow depletion from groundwater pumping, we argue that a new groundwater presumptive standard is critical as a placeholder to protect environmental flows in rivers lacking detailed assessments. We thus extend the previous presumptive standard to groundwater pumping, a different and important driver of changes to streamflow. We suggest that “high levels of ecological protection will be provided if groundwater pumping decreases monthly natural baseflow by less than 10% through time.” The presumptive standard is intended to be a critical placeholder only where detailed scientific assessments of environmental flow needs cannot be undertaken in the near term. We also suggest a new metric, the environmental flow response time, that allows water managers to quantify the timescales of the impacts of groundwater pumping on the loss or gain of environmental flows.

Proposing environmental flows based on physical habitat simulation for five fish species in the Lower Duero River Basin, Mexico

Background. The concept of “environmental flow” is defined as hydrologic regimes that are required to sustain ecosystem health and functions in rivers. In Mexico, it has become an important topic, not least because a 2012 legal standard (NMX-AA-159-SCFI-2012), establishes procedures for determining instream flow requirements. Goals. The aim of this paper is to propose an acceptable environmental flow requirement for a regulated river segment in the Duero River Basin in, Michoacan, Mexico. Methods. Of the many methods of establishing environmental flows in rivers, this article is concerned with the habitat simulation method. This is based on the IFIM theoretical framework and the PHABSIM mathematical model, by which the WUA-Q curves were obtained for five species of fish. Results . From these curves, we determined that the Goodea atripinnis species has the greater habitat area and reached a maximum of 4338 m2/km for a flow of 5 m3/s; Alloophorus robustus maintained a constant habitat of 2000 m2/km between flow rates of 5 to 15 m3/s. With smaller area, Menidia jordani had a maximum habitat of 1323 m2/km for 4.5 m3/s; and with WUA less than 500 m2/km the curves of the species Algansea tincella and Aztecula sallaei were obtained. Conclusions. The average regulation in March and April was 3.61 and 3.44 m3/s and with the EFR proposal it was 5.11 and 5.00 m3/s for March and April, respectively. In general, the monthly environmental regime is to maintain 80% of the natural flow regime, generating an increase in habitat during the dry season of 24% for A. robustus and 23% for A. sallaei.

Response of the fish assemblage to a saltwater barrier and paper mill effluent in the Lower Neches River (Texas) during drought

ABSTRACTIn 2011, Texas experienced record heat and drought that escalated concerns about environmental flows for rivers. In response to these worries, fishes and water quality were sampled in the Lower Neches River, Texas, from May-August 2012 during continued drought. Potential effects of hydrology on environmental parameters and assemblages of small (seine samples) and large (gillnet samples) fishes were evaluated at multiple locations. Approximately 1 km downstream from the saltwater barrier, paper mill effluent discharges into the river. Salinity was higher and dissolved oxygen lower below the saltwater barrier during low-flow intervals. Fish species richness in seine samples, was higher when the barrier was open, and species richness for both gear types was lowest at sites closest to the paper mill effluent discharge. Overall, species richness was higher at sites below the barrier, with more estuarine and marine species present. When the barrier was closed, richness and abundance of sensitive freshwater species were lower below the barrier. Closure of the barrier during drought results in accumulation of dissolved organic compounds from paper mill effluent and lower dissolved oxygen in the reach below the barrier. To sustain biodiversity in the system, subsistence flows must pass across the saltwater barrier during droughts.

A new habitat methodology for river environmental flow requirements

This paper introduces a new framework for habitat methodology to identify the environmental flow requirements for rivers using bioecological, hydrological and hydraulic criteria. Using the new method, the environmental flow of the Gorganrud River in Iran is calculated for all months of the year using the critical months' ratio as a guide. Although the critical environmental flow is calculated as twice that calculated by the Tennant method, the annual average outflow to the sea is only 1% more. Moreover, there are the same benefits for the two methods, including maintaining flows to the estuary throughout the year and flood risk management around 30% of the time. However, the probability of environmental flow demand in critical months is increased from 67% in the Tennant method to 100% using the new method. There are also positive significant effects on water basin management, such as an emphasis on the maintenance of environmental aspects, specifically in the spring and summer months, in comparison with the Tennant method. The Tennant method is therefore not recommended for use in defining environmental flow in the Gorganrud basin or in the north of Iran.

Evaluation of environmental flow requirements using eco-hydrologic-hydraulic methods in perennial rivers.

The assessment of environmental flows in rivers is of vital importance for preserving riverine ecosystem processes. This paper addresses the evaluation of environmental flow requirements in three reaches along a typical perennial river (the Zab transboundary river, in north-west Iran), using different hydraulic, hydrological and ecological methods. The main objective of this study came from the construction of three dams and inter-basin transfer of water from the Zab River to the Urmia Lake. Eight hydrological methods (i.e. Tennant, Tessman, flow duration curve analysis, range of variability approach, Smakhtin, flow duration curve shifting, desktop reserve and 7Q2&10 (7-day low flow with a 2- and 10-year return period)); two hydraulic methods (slope value and maximum curvature); and two habitat simulation methods (hydraulic-ecologic, and Q Equation based on water quality indices) were used. Ecological needs of the riverine key species (mainly Barbus capito fish), river geometries, natural flow regime and the environmental status of river management were the main indices for determining the minimum flow requirements. The results indicate that the order of 35%, 17% and 18% of the mean annual flow are to be maintained for the upper, middle and downstream river reaches, respectively. The allocated monthly flow rates in the three Dams steering program are not sufficient to preserve the Zab River life.

Ecological operation for Three Gorges Reservoir

The traditional operation of the Three Gorges Reservoir has mainly focused on water for flood control, power generation, navigation, water supply, and recreation, and given less attention to the negative impacts of reservoir operation on the river ecosystem. In order to reduce the negative influence of reservoir operation, ecological operation of the reservoir should be studied with a focus on maintaining a healthy river ecosystem. This study considered ecological operation targets, including maintaining the river environmental flow and protecting the spawning and reproduction of the Chinese sturgeon and four major Chinese carps. Using flow data from 1900 to 2006 at the Yichang gauging station as the control station data for the Yangtze River, the minimal and optimal river environmental flows were analyzed, and eco-hydrological targets for the Chinese sturgeon and four major Chinese carps in the Yangtze River were calculated. This paper proposes a reservoir ecological operation model, which comprehensively considers flood control, power generation, navigation, and the ecological environment. Three typical periods, wet, normal, and dry years, were selected, and the particle swarm optimization algorithm was used to analyze the model. The results show that ecological operation modes have different effects on the economic benefit of the hydropower station, and the reservoir ecological operation model can simulate the flood pulse for the requirements of spawning of the Chinese sturgeon and four major Chinese carps. According to the results, by adopting a suitable re-operation scheme, the hydropower benefit of the reservoir will not decrease dramatically while the ecological demand is met. The results provide a reference for designing reasonable operation schemes for the Three Gorges Reservoir.

Quantifying impacts of climate variability and human activities on the hydrological system of the Haihe River Basin, China

In the last 50 years, the hydrological system of the Haihe River Basin in northern China has undergone great changes, such as declines in runoff and discharge, rivers drying up, and groundwater depletion. Both climate variability and human activities have been regarded as causes for these changes, but which is the major reason was not clear in the past. This paper aims to quantify the impact of climate variability, particularly changes of precipitation, and human activities (water storage projects, agricultural development, soil and water conservation projects, and agricultural water saving) on the hydrological system of the basin. A basin-level water consumption balance model was used to simulate the changes of the hydrological system during the period of 1958–2008. The non-parametric Mann–Kendall test and Pettitt’s test methods were adopted to identify trends and change points of the hydrological factors. And the contribution of climatic variability and human activities was calculated based on the multi-year average of all the climatic and hydrological parameters of different river basin management stages and their relative changes between adjacent periods. The results show that from 1958 to 1965 the basin hydrological system was in the natural state of equilibrium. During 1966–1978 human activities were the main factors with the contribution of 96.1 and 76.6 % for the upstream and downstream area. During the period of 1979–1988, the change of precipitation was the main factor to cause the upstream and downstream hydrological system changes with contributions of 73.8 and 64.1 %. In the period of 1989–2000 and 2001–2008, the climate variability still dominated the impact of the hydrological system changes in the upstream and downstream areas. Based on these findings, some measures were recommended to improve the balance of the hydrological system in this basin including recharging the downstream area with water that is currently stored in the upstream, implementing agricultural water-saving practices in the basin, and using treated sewage from the cities for river environmental flow recovery and wetland restoration.