Protection Of Riverine Ecosystems Research Articles

Ecological flow research in response to hydrological variation: A case study of the Jinsha River Basin, China

Climate change and human activities have altered the natural state of rivers to a certain extent, leading to runoff variation and impacting the stability of riverine ecosystems. The ecological flow has emerged to balance the water relationship between humanity and riverine ecosystems and to safeguard the health and biodiversity of rivers. Presently, the scientific quantification of riverine ecological flow has become a focal point in water resource research. Addressing the quantification of ecological flow under hydrological variation conditions, the cumulative deviation method (CDM) and Pettitt methods were firstly employed to detect breakpoints in the runoff sequences. Then, the natural monthly runoff post-variation was restored using the Soil and Water Assessment Tool (SWAT) model, i.e., natural runoff restoration, and three testing methods were employed to determine the optimal hydrological distribution functions for natural monthly runoff. Subsequently, an improved frequency calculation method was used to calculate the ecological flow. The Jinsha River Basin was selected as the study area, and four crucial sections in the mainstream of the Jinsha River were studied, including Zhimenda (ZMD), Shigu (SG), Xiaodeshi (XDS), and Pingshan (PS). The results indicated: (1) the runoff sequences (1960–2017) at the four crucial sections exhibit different breakpoint times, with breakpoint years being 2004, 1986, 2005, and 1996, respectively; (2) the SWAT model, in simulating runoff at the four crucial sections, exhibited NSE values all exceeding 0.85, and r values all surpassing 0.9, demonstrating its effective ability to restore natural runoff in the Jinsha River basin; (3) the optimal hydrological distribution functions for natural monthly runoff at the four sections varied, and most natural monthly runoff conforms to the Generalized Extreme Value (GEV) distribution; (4) the average annual ecological flows for the ZMD, SG, XDS, and PS sections were 296 m3/s, 992 m3/s, 1238 m3/s, and 2755 m3/s, and the ecological flows derived using the improved frequency calculation method under the optimal hydrological distribution functions were more rational. This study can provide a scientific basis for the optimal allocation of water resources and the protection of riverine ecosystems in the Jinsha River basin.

An integrated approach to support a river ecological network: A case study from the Mediterranean

Riverine ecosystems are among the most impacted ecosystems worldwide since they are exposed to multiple stressors. Land Use/Land Cover (LULC) changes is the main human imprint on those ecosystems whose spatiotemporal habitat destructions pose a threat to biodiversity, ecosystem integrity and ecological processes. The most important statutory instruments for riverine ecosystem protection, conservation and restoration in the European Union are the Water Framework Directive (WFD) and the Habitats and Birds Directive (HBDs). In this study, we develop a methodological framework to spatially link the ecological integrity of river sub-basins with the protected areas therein, taking into account the influence of land use as expressed in the WFD. We combined a multi-criteria evaluation approach using six of the most frequently applied criteria for conservation evaluation to assess river basin integrity (RBI) index at the sub-basin level, and used as a proxy for functional connectivity categories. In addition, we used the distance of every sub-basin from the surrounding Natura 2000 sites as a measure of structural connectivity. Using ecological network design principles (i.e. Core areas; Corridors; Stepping Stones; Buffer areas; and Restoration areas), we incorporated the two aspects of connectivity into a framework, which links river management at the basin level with the site level assessment as dictated by the HBDs. We implemented this framework in a Mediterranean river basin located in Southern Tuscany, which is part of the Natura 2000 network. Six of the sub-basins (20%) have high functional connectivity, 14 sub-basins (47%) medium and 10 sub-basins (33%) low functional connectivity. Structural connectivity of the study area followed the same tendency as that of functional connectivity, with the majority of the sub-basins having medium connectivity (57%; 17 sub-basins), and 23% (7 sub-basins) and 20% (6 sub-basins) high and low structural connectivity respectively. As a result, six of the sub-basins were characterised as corridor areas while the majority of the sub-basins were identified as buffer areas (57%). Two sub-basins were characterised restoration areas and one as stepping stone (SS). Our approach is one of many plausible ecological networks, which although analytically simple, can be enriched with data on species and stakeholders’ involvement.

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.

Reduction in the phytoplankton index of biotic integrity in riverine ecosystems driven by industrial activities, dam construction and mining: A case study in the Ganjiang River, China

Industrial activities, dam construction, and mining are three human activities important for societal and economic development. However, the effects of these activities on phytoplankton communities have been less quantitatively assessed than those on other groups, such as macroinvertebrates, fish, and periphytic algae. In the present study, we selected the Ganjiang River basin, a tributary of the Yangtze River as the representative area to develop a feasible phytoplankton index of biotic integrity (Phyto-IBI) to evaluate the effects of industrial activities, dam construction, and mining on the biotic integrity of riverine ecosystems. The results showed that the three activities greatly altered the abundance and composition of phytoplankton, with a reduction in phytoplankton species quantity and diversity and an increase in abundance. The health status of the Ganjiang River was fair, and the health statuses of industrial areas, dam areas, mining areas, and reference points were poor, poor, fair, and good, respectively. The three activities damaged the biotic integrity of the aquatic system. Moreover, compared to industrial activities and mining, dam construction is more harmful to aquatic systems in the Ganjiang River. The locally weighted regression scatter plot smoother (LOWESS) method showed that an ammonium nitrogen (NH3-N) concentration of 0.65 mg L−1 is the environmental protection threshold for planktonic biotic integrity in the Ganjiang River. This study not only quantitatively assesses phytoplankton responses to industrial activities, dam construction, and mining but also provides guidance regarding the ecological monitoring, assessment and protection of riverine ecosystems.

A nature-based reservoir optimization model for resolving the conflict in human water demand and riverine ecosystem protection

Although construction of reservoirs and dams is one of the most common approaches to satisfy water demand and alleviate water scarcity, this approach severely affects river ecosystems. The most direct impact of human activities on rivers, for instance, regulating river can lead to degraded riverine ecosystems as part of the hydrological alteration. This paper determines the available ratio of water resource of natural or semi-natural rivers for ecological feasible regions using a method that transcends the traditional perspective of designed environmental flow. Our framework involves a modified percent of flow approach to identify the ecological feasible region of water resources utilization, which sequentially acts as a constraint for a reservoir optimization model based on the Cuckoo Search algorithm to obtain an optimal diversion process. Indicators of the hydrological alteration statistical method and the histogram matching approach are used to examine the framework's performance. The Han to Wei inter-basin water transfer project of China is selected as a case study. Results indicate that: (1) the allowable diversion rate with this modified percent of flow approach is more effective for reducing interference of diversion on the ecosystems than the conventional planned diversion rule; water demand, however, cannot be satisfied by the allowable diversion rate; (2) ecological feasible region is an accessible constraint for reservoir operation model, and the optimal diversion rate of such model is a trade-off output between the human water demand and the riverine ecosystems protection; and (3) increased allowable diversion rates alter flow indicators including the February flow, 30-day minimum flow, and low pulse count more appreciably than does the optimal diversion rate. This study provides key insights on how to achieve a trade-off between human water demand and riverine ecosystems protection, therefore contributing to the local sustainable development of social economy and ecological environment.

Characteristics and Practices of Ecological Flow in Rivers with Flow Reductions Due to Water Storage and Hydropower Projects in China

Water and flow reductions in the channels downstream of water storage and hydropower projects have significant impacts on aquatic ecosystems. Understanding and analyzing the ecosystem status is of great significance to facilitate the protection of riverine ecosystems. A database was established based on the 2000–2017 environmental impact assessment (EIA) reports on water storage and hydropower projects in China, and corresponding analysis software was built based on an ArcGIS spatial analysis platform. The projects in China are mainly found in the Yangtze and Pearl River basins and in south-western China. The hydropower projects have a larger influence than the water storage projects on the flow of downstream rivers sections, and most of the hydropower projects, especially the water diversion projects, cause flow reductions in the downstream rivers. An ecological flow management mechanism in China implemented in 2006 provided a promising method to alleviate river flow reductions. However, there is still only one kind of ecological flow calculation method and few ecological flow regulation measures in use. Based on the advantages and problems of the existing ecological flow management system, this paper proposes a management scheme based on a regional-engineering calculation method. The results can facilitate decision making in ecological flow management.

Quantifying parameter uncertainty in reservoir operation associated with environmental flow management

Parameter uncertainty inherent in reservoir operation affects operation model robustness and has been considered in conventional operation focusing on improving hydropower generation. With more attention paid to ecological environment protection recently, riverine ecosystem protection requires environmental flow (e-flow) management to sustain a near-natural flow regime. Whether there is e-flow management in reservoir operation has an impact on the uncertainty of reservoir operation, but parameter uncertainty was rarely considered in reservoir operation with e-flow management. In this study, a framework is proposed for performing parameter uncertainty analysis in reservoir operation associated with e-flow management. Both e-flow requirements and hydropower generation are considered in reservoir operation to sustain the harmonious development between ecological environment and human society. To compare the effect of different e-flow managements on the uncertainty of reservoir operation, three e-flow management scenarios are set. The Metropolis-Hastings algorithm of Markov Chain Monte Carlo (MCMC) sampling approach was applied for parameter estimation and uncertainty quantification. We used this framework in a case study of Nuozhadu hydropower station on the Lancang River in southern China to test its effectiveness. The results demonstrated that parameter uncertainty greatly affects the robustness of reservoir operation model. The comparison of reservoir operation under different e-flow management scenarios shows that more detailed e-flow management can effectively reduce uncertainty in reservoir operation and sustain the near-natural flow regime in a river.

Using radon to understand parafluvial flows and the changing locations of groundwater inflows in the Avon River, southeast Australia

Abstract. Understanding the location and magnitude of groundwater inflows to rivers is important for the protection of riverine ecosystems and the management of connected groundwater and surface water systems. This study utilizes 222Rn activities and Cl concentrations in the Avon River, southeast Australia, to determine the distribution of groundwater inflows and to understand the importance of parafluvial flow on the 222Rn budget. The distribution of 222Rn activities and Cl concentrations implies that the Avon River contains alternating gaining and losing reaches. The location of groundwater inflows changed as a result of major floods in 2011–2013 that caused significant movement of the floodplain sediments. The floodplain of the Avon River comprises unconsolidated coarse-grained sediments with numerous point bars and sediment banks through which significant parafluvial flow is likely. The 222Rn activities in the Avon River, which are locally up to 3690 Bq m−3, result from a combination of groundwater inflows and the input of water from the parafluvial zone that has high 222Rn activities due to 222Rn emanation from the alluvial sediments. If the high 222Rn activities were ascribed solely to groundwater inflows, the calculated net groundwater inflows would exceed the measured increase in streamflow along the river by up to 490 % at low streamflows. Uncertainties in the 222Rn activities of groundwater, the gas transfer coefficient, and the degree of hyporheic exchange cannot explain a discrepancy of this magnitude. The proposed model of parafluvial flow envisages that water enters the alluvial sediments in reaches where the river is losing and subsequently re-enters the river in the gaining reaches with flow paths of tens to hundreds of metres. Parafluvial flow is likely to be important in rivers with coarse-grained alluvial sediments on their floodplains and failure to quantify the input of 222Rn from parafluvial flow will result in overestimating groundwater inflows to rivers.

An optimal hydropower contract load determination method considering both human and riverine ecosystem needs

In this research, a new method is developed to determine the optimal contract load for a hydropower reservoir, which is achieved by incorporating environmental flows into the determination process to increase hydropower revenues, while mitigating the negative impacts of hydropower generation on riverine ecosystems. In this method, the degree of natural flow regime alteration is adopted as a constraint of hydropower generation to protect riverine ecosystems, and the maximization of mean annual revenue is set as the optimization objective. The contract load in each month and the associated reservoir operating parameters were simultaneously optimized by a genetic algorithm. The proposed method was applied to China’s Wangkuai Reservoir to test its effectiveness. The new method offers two advantages over traditional studies. First, it takes into account both the economic benefits and the ecological needs of riverine systems, rather than only the economic benefits, as in previous methods. Second, although many measures have been established to mitigate the negative ecological impacts of hydropower generation, few have been applied to the hydropower planning stage. Thus, since the contract load is an important planning parameter for hydropower generation, influencing both economic benefits and riverine ecosystem protection, this new method could provide guidelines for the establishment of river protection measures at the hydropower planning stage.

Portfolio optimisation for hydropower producers that balances riverine ecosystem protection and producer needs

Abstract. In deregulated electricity markets, hydropower portfolio design has become an essential task for producers. The previous research on hydropower portfolio optimisation focused mainly on the maximisation of profits but did not take into account riverine ecosystem protection. Although profit maximisation is the major objective for producers in deregulated markets, protection of riverine ecosystems must be incorporated into the process of hydropower portfolio optimisation, especially against a background of increasing attention to environmental protection and stronger opposition to hydropower generation. This research seeks mainly to remind hydropower producers of the requirement of river protection when they design portfolios and help shift portfolio optimisation from economically oriented to ecologically friendly. We establish a framework to determine the optimal portfolio for a hydropower reservoir, accounting for both economic benefits and ecological needs. In this framework, the degree of natural flow regime alteration is adopted as a constraint on hydropower generation to protect riverine ecosystems, and the maximisation of mean annual revenue is set as the optimisation objective. The electricity volumes assigned in different electricity submarkets are optimised by the noisy genetic algorithm. The proposed framework is applied to China's Wangkuai Reservoir to test its effectiveness. The results show that the new framework could help to design eco-friendly portfolios that can ensure a planned profit and reduce alteration of the natural flow regime.

A reservoir operating method for riverine ecosystem protection, reservoir sedimentation control and water supply

• Water level and sediment volume are triggers of sediment flushing. • Reservoir operating rule curves are changed from “static” to “dynamic” ones. • Both the flow and sediment regimes are considered for river protection. Riverine ecosystem protection requires the maintenance of natural flow and sediment regimes downstream from dams. In reservoir management schedules this requirement should be integrated with sedimentation control and human water supply. However, traditional eco-friendly reservoir operating methods have usually only considered the natural flow regime. This paper seeks to develop a reservoir operating method that accounts for both the natural flow and sediment regimes as well as optimizing the water supply allocations. Herein, reservoir water level (RWL), sediment-occupied ratio of reservoir volume (SOR) and rate of change of SOR (RCSOR) are adopted as three triggers of a drawdown-flushing-based sediment management policy. Two different groups of reservoir operating rule curves (RORCs) are designed for sediment-flushing and non-sediment-flushing years, and the three triggers, RWL, SOR and RCSOR, are used to change the “static” RORCs to “dynamic” ones. The approach is applied to the Wangkuai Reservoir, China to test its effectiveness. This shows that the approach can improve the flexibility of reservoir operators to balance the reservoir management, water supply management and the flow and sediment needs of the downstream riverine ecosystem.

Riverine ecosystem services and the thermoelectric sector: strategic issues facing the Northeastern United States

Major strategic issues facing the global thermoelectric sector include environmental regulation, climate change and increasing electricity demand. We have addressed such issues by modeling thermoelectric generation in the Northeastern United States that is reliant on cooling under five sensitivity tests to evaluate losses/gains in power production, thermal pollution and suitable aquatic habitat, comparing the contemporary baseline (2000–2010) with potential future states. Integral to the analysis, we developed a methodology to quantify river water availability for cooling, which we define as an ecosystem service. Projected climate conditions reduce river water available for efficient power plant operations and the river’s capacity to absorb waste heat, causing a loss of regional thermoelectric generation (RTG) (2.5%) in some summers that, compared to the contemporary baseline, is equal to the summertime electricity consumption of 1.3 million Northeastern US homes. Vulnerabilities to warm temperatures and thermal pollution can be alleviated through the use of more efficient natural gas (NG) power plants that have a reduced reliance on cooling water. Conversion of once-through (OT) to cooling tower (CT) systems and the Clean Water Act (CWA) temperature limit regulation, both of which reduce efficiencies at the single plant level, show potential to yield beneficial increases in RTG. This is achieved by obviating the need for large volumes of river water, thereby reducing plant-to-plant interferences through lowering the impact of upstream thermal pollution and preserving a minimum standard of cooling water. The results and methodology framework presented here, which can be extrapolated to other regional assessments with contrasting climates and thermoelectric profiles, can identify opportunities and support decision-making to achieve more efficient energy systems and riverine ecosystem protection.

A dynamic model to assess tradeoffs in power production and riverine ecosystem protection

Major strategic planning decisions loom as society aims to balance energy security, economic development and environmental protection. To achieve such balance, decisions involving the so-called water-energy nexus must necessarily embrace a regional multi-power plant perspective. We present here the Thermoelectric Power & Thermal Pollution Model (TP2M), a simulation model that simultaneously quantifies thermal pollution of rivers and estimates efficiency losses in electricity generation as a result of fluctuating intake temperatures and river flows typically encountered across the temperate zone. We demonstrate the model's theoretical framework by carrying out sensitivity tests based on energy, physical and environmental settings. We simulate a series of five thermoelectric plants aligned along a hypothetical river, where we find that warm ambient temperatures, acting both as a physical constraint and as a trigger for regulatory limits on plant operations directly reduce electricity generation. As expected, environmental regulation aimed at reducing thermal loads at a single plant reduces power production at that plant, but ironically can improve the net electricity output from multiple plants when they are optimally co-managed. On the technology management side, high efficiency can be achieved through the use of natural gas combined cycle plants, which can raise the overall efficiency of the aging population of plants, including that of coal. Tradeoff analysis clearly shows the benefit of attaining such high efficiencies, in terms of both limiting thermal loads that preserve ecosystem services and increasing electricity production that benefits economic development.

Suitable Environmental Flow Release Criteria for Both Human and Riverine Ecosystems: Accounting for the Uncertainty of Flows

Environmental flow (e‐flow) release criteria are key parameters in water resources management and riverine ecosystem protection. The previous methods for e‐flow criterion determination are based on the historical flow time series without the consideration of flow uncertainty. Due to low possibility of reoccurrence of the historical flows and the uncertainty of future flows, the flow uncertainty needs to be integrated in the process of determining e‐flow release criteria. In this research, a new method is proposed to determine the optimal e‐flow release criteria under flow uncertainty accounting for both the human and riverine ecosystem needs. In the new method, the scenario tree method is applied to generate the scenarios of flows, which can cover most of possible flow conditions and can effectively reflect the uncertainty of flows; the Range of Variability Approach (RVA), a most commonly used method to assess the flow regime alteration, is refined by incorporating the uncertainty of flows. The Tang River in Northern China is taken as a case study to test the effectiveness of the new method. The results show that the previous method obviously overestimates the optimal e‐flow release criteria and the new method can get more suitable criteria that are suitable for both human and riverine ecosystems.

OPTIMIZING ENVIRONMENTAL FLOWS BELOW DAMS

ABSTRACTThe protection of riverine ecosystems downstream from dams requires reservoir operations to satisfy environmental flow (e‐flow) requirements. In practice, this often involves re‐regulation of downstream river flows within the constraints of water resource demands for human supplies and irrigation. In this paper, we develop a method to assess how reservoir storage may be used more effectively to meet both water supply and downstream ecosystem needs. The latter are met by providing seasonally variable baseflows, including dry season flow recession at natural rates, and high‐flow pulses and bankfull flows synchronized with natural events. A series of reservoir operating rules are derived based on both reservoir storage and reservoir inflows to trigger reservoir releases. For a given water supply reliability, the method seeks to minimize the degree of hydrological alteration below a dam. We present a case study of the Tanghe Reservoir in China's Tang river basin to show that the proposed method could help reservoir managers and planners evaluate e‐flow scenarios to reduce the negative impacts of dams and reservoirs on riverine ecosystems. Copyright © 2010 John Wiley & Sons, Ltd.

Floristic composition and diversity of three swamp forests in northwest Guyana

This paper reviews the floristic composition, vegetation structure, and diversity of three types of swamp forest that cover a considerable part of Guyana's North-West District. Trees, shrubs, lianas, herbs, and hemi-epiphytes were inventoried in three hectare plots: one in Mora forest, one in quackal swamp, and one in manicole swamp. The Mora forest, flooded annually by white water, was dominated by relatively few, large individuals of Mora excelsa. The very dense, thin-stemmed quackal forest, almost permanently flooded by black water, was characterized by Tabebuia insignis and Symphonia globulifera and contained few palms. The somewhat less dense manicole swamp, flooded regularly by brackish water, was distinguished by large numbers of Euterpe oleracea. Although the three swamps showed little overlap in floristic composition and densities of dominant species, they represent some of the lowest diversity forest in the Neotropics, with an α-diversity of 7.4 for the Mora forest, 8.2 for the quackal forest and 5.7 for the manicole swamp. When compared with similar vegetation types in the Guiana Shield, the swamp forests in this study show some interesting differences in species composition and density. The wetlands of the North-West District form the last stretch of natural coastline in Guyana and play an important role in the protection of riverine ecosystems. Furthermore, there is commercial potential for the extraction of non-timber forest products from these low-diversity forests. Nevertheless, in prolonged dry periods, large tracts of quackal forest are being burnt to give way to almost treeless, flooded savannas. For these reasons, adequate management and conservation strategies must be developed for the area.