Environmental flows for natural, hybrid, and novel riverine ecosystems in a changing world (original) (raw)
Ecohydrology, 2015
Water resource development and drought have altered river flow regimes, increasing average flood return intervals across floodplains in the Murray-Darling Basin, Australia, causing health declines in riparian river red gum (Eucalyptus camaldulensis) forests and woodlands. Environmental flow allocations helped to alleviate water stress during the recent Millennium Drought (1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010); however, quantification of the flood frequency required to support healthy E. camaldulensis communities is still needed. We quantified water requirements of E. camaldulensis for 2 years across a flood gradient (trees inundated at frequencies of 1:2, 1:5 and 1:10 years) at Yanga National Park, New South Wales, to help inform management decision-making and design of environmental flows. Sap flow, evaporative losses and soil moisture measurements were used to determine transpiration, evapotranspiration and plant-available soil water before and after flooding. A formula was developed using plant-available soil water post-flooding and average annual rainfall, to estimate maintenance time of soil water reserves in each flood frequency zone. Results indicated that soil water reserves could sustain 1:2 and 1:5 trees for 15 months and 6 years, respectively. Trees regulated their transpiration rates, allowing them to persist within their flood frequency zone, and showed reduction in active sapwood area and transpiration rates when flood frequencies exceeded 1:2 years. A leaf area index of 0·5 was identified as a potential threshold indicator of severe drought stress. Our results suggest that environmental water managers may have greater flexibility to adaptively manage floodplains in order to sustain E. camaldulensis forests and woodlands than has been appreciated hitherto.
The changing hydrology of a dammed Amazon
Science advances, 2017
Developing countries around the world are expanding hydropower to meet growing energy demand. In the Brazilian Amazon, >200 dams are planned over the next 30 years, and questions about the impacts of current and future hydropower in this globally important watershed remain unanswered. In this context, we applied a hydrologic indicator method to quantify how existing Amazon dams have altered the natural flow regime and to identify predictors of alteration. The type and magnitude of hydrologic alteration varied widely by dam, but the largest changes were to critical characteristics of the flood pulse. Impacts were largest for low-elevation, large-reservoir dams; however, small dams had enormous impacts relative to electricity production. Finally, the "cumulative" effect of multiple dams was significant but only for some aspects of the flow regime. This analysis is a first step toward the development of environmental flows plans and policies relevant to the Amazon and othe...
Flow intermittence and ecosystem services in rivers of the Anthropocene
Journal of Applied Ecology
1. Intermittent rivers and ephemeral streams (IRES) are watercourses that cease flow at some point in time and space. Arguably Earth's most widespread type of flowing water, IRES are expanding where Anthropocenic climates grow drier and human demands for water escalate. 2. However, IRES have attracted far less research than perennial rivers and are undervalued by society, jeopardizing their restoration or protection. Provision of ecosystem services by IRES is especially poorly understood, hindering their integration into management plans in most countries. 3. We conceptualize how flow intermittence governs ecosystem service provision and transfers at local and river-basin scales during flowing, non-flowing and dry phases. Even when dry or not flowing, IRES perform multiple ecosystem services that complement those of nearby perennial rivers. 4. Synthesis and applications. Conceptualizing how flow intermittence in rivers and streams governs ecosystem services has applied a socio-ecological perspective for validating the ecosystem services of intermittent rivers and ephemeral streams. This can be applied at all flow phases and in assessing impacts of altered flow intermittence on rivers and their ecosystem services in the Anthropocene.
Effects of human-driven water stress on river ecosystems: a meta-analysis
Scientific reports, 2018
Human appropriation of water resources may induce water stress in freshwater ecosystems when ecosystem needs are not met. Intensive abstraction and regulation cause river ecosystems to shift towards non-natural flow regimes, which might have implications for their water quality, biological structure and functioning. We performed a meta-analysis of published studies to assess the potential effects of water stress on nutrients, microcontaminants, biological communities (bacteria, algae, invertebrates and fish), and ecosystem functions (organic matter breakdown, gross primary production and respiration). Despite the different nature of the flow regime changes, our meta-analysis showed significant effects of human-driven water stress, such as significant increases in algal biomass and metabolism and reduced invertebrate richness, abundance and density and organic matter decomposition. Water stress also significantly decreased phosphate concentration and increased the concentration of ph...
The impact of flooding on aquatic ecosystem services
Biogeochemistry
Flooding is a major disturbance that impacts aquatic ecosystems and the ecosystem services that they provide. Predicted increases in global flood risk due to land use change and water cycle intensification will likely only increase the frequency and severity of these impacts. Extreme flooding events can cause loss of life and significant destruction to property and infrastructure, effects that are easily recognized and frequently reported in the media. However, flooding also has many other effects on people through freshwater aquatic ecosystem services, which often go unrecognized because they are less evident and can be difficult to evaluate. Here, we identify the effects that small magnitude frequently occurring floods (\ 10-year recurrence interval) and extreme floods ([ 100-year recurrence interval) have on ten aquatic ecosystem services through a systematic literature review. We focused on ecosystem services considered by the Millennium Ecosystem Assessment including: (1) supporting services (primary production, soil formation), (2) regulating services (water regulation, water quality, disease regulation, climate regulation), (3) provisioning services (drinking water, food supply), and (4) cultural services (aesthetic value, recreation and tourism). The literature search resulted in 117 studies and each of the Responsible Editor: Sujay Kaushal.
The Brisbane Declaration and Global Action Agenda on Environmental Flows (2018)
Frontiers in Environmental Science
respect for their rights, responsibilities and systems of governance in environmental water decisions. These social and cultural dimensions of e-flow management warrant far more attention. Actionable recommendations present a pathway forward for a new era of scientific research and innovation, shared visions, collaborative implementation programs, and adaptive governance of environmental flows, suited to new social, and environmental contexts driven by planetary pressures, such as human population growth and climate change.
Wiley Interdisciplinary Reviews: Water
Environmental water management is a relatively new discipline, with concepts, management practice and institutional mechanisms that are still emerging. The efficient and effective use of environmental water to maximize environmental benefits, or environmental water use efficiency, is one such emerging concept. Currently, much of the focus is on allocative efficiency, where the objective is to achieve a better balance between consumptive and environmental water uses in a cost-effective way. However, this may not provide the most efficient and effective way to manage environmental water in the long term, where managers are seeking productive (or operational) efficiency. Here, the objective is to maximize environmental outcomes relative to the cost of managing the available resource. This paper explores the concept of water use efficiency in the context of environmental water.
Research Priorities to Improve Future Environmental Water Outcomes
Frontiers in Environmental Science
Significant progress in environmental flow management has occurred in recent years due to several factors. These include governments committing to environmental flow programs, significant progress in scientific understanding, and environmental flow assessment methods that are cognizant of stakeholder participation and co-design. However, there remain key challenges facing environmental water management. In this paper, we report on a horizon scanning exercise that identified the questions, which, if answered, would deliver much needed progress in the field of environmental water management. We distributed an online survey to ask researchers and practitioners in the field of environmental water management to identify the key questions. The authors then consolidated 268 submitted questions and organized them into key themes. The consolidated list was presented to a workshop of environmental water researchers and practitioners, where attendees were asked to review the questions, vote on the most important, and provide feedback on gaps, issues, or overlaps. The breadth of issues facing environmental water management is captured by the six key themes into which questions were classified: (1) Ecological knowledge and environmental flow assessment methods, (2) Adaptive management, (3) Integrated management and river objectives, (4) Knowledge transfer: applying best practice in a global context, (5) Community knowledge and engagement, and (6) Active management. These questions provide a roadmap for research and management innovations that will improve the effectiveness of environmental flows programs.
Transforming Environmental Water Management to Adapt to a Changing Climate
Frontiers in Environmental Science
Environmental water management has become a global imperative in response to environmental degradation and the growing recognition that human well-being and livelihoods are critically dependent on freshwater ecosystems and the ecological functions and services they provide. Although a wide range of techniques and strategies for planning and implementing environmental flows has developed, many remain based on assumptions of hydrologic stationarity, typically focusing on restoring freshwater ecosystems to pre-development or "natural" conditions. Climate change raises major challenges to this conventional approach, in part because of increasing uncertainties in patterns of water supply and demand. In such a rapidly changing world, the implementation of, and capacity of water managers to deliver flow regimes resembling historical hydrological patterns may be both unfeasible and undesirable. Additionally, as emphasis shifts from species-focused water allocation plans toward a greater appreciation of freshwater ecological functions and services, many of which will be influenced by climate change, a thorough re-evaluation of the conventional objectives, planning, delivery and monitoring of environmental water, including its role in the broader context of water and environmental management, is essential. Here, we identify the major challenges posed by climate change to environmental water management and discuss key adaptations and research needed to meet these challenges to achieve environmental and societal benefits and avoid maladaptation.
Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan
BioScience
Despite their limited spatial extent, freshwater ecosystems host remarkable biodiversity, including one-third of all vertebrate species. This biodiversity is declining dramatically: Globally, wetlands are vanishing three times faster than forests, and freshwater vertebrate populations have fallen more than twice as steeply as terrestrial or marine populations. Threats to freshwater biodiversity are well documented but coordinated action to reverse the decline is lacking. We present an Emergency Recovery Plan to bend the curve of freshwater biodiversity loss. Priority actions include accelerating implementation of environmental flows; improving water quality; protecting and restoring critical habitats; managing the exploitation of freshwater ecosystem resources, especially species and riverine aggregates; preventing and controlling nonnative species invasions; and safeguarding and restoring river connectivity. We recommend adjustments to targets and indicators for the Convention on B...
Ecological responses to flow variation inform river dolphin conservation
Scientific Reports, 2020
Many environmental flow (e-flow) studies and applications have predominantly used state—(i.e., at a single time point) and rate—(i.e., temporal change) based demographic characteristics of species representing lower trophic levels (e.g., fish communities) to build flow-ecology relationships, rather than using a process that incorporates population dynamics. Recent studies have revealed the importance of incorporating data on species traits when building flow-ecology relationships. The effects of flow on keystone megafauna species (i.e., body mass ≥ 30 kg) reverberate through entire food webs; however, the relationships between flow and these species are not well understood, limiting the scope of the relationships used in flow management. Here, we fill this gap by incorporating the habitat selection traits at different flows of a freshwater apex predator, Ganges River dolphin (GRD, Platanista gangetica gangetica), which plays a significant role in maintaining the structure, functions...
Water
Determination of environmental flows at the regional scale has been complicated by the fine-scale variability of the needs of aquatic organisms. Therefore, most regional methods are based on observation of hydrological patterns and lack evidence of connection to biological responses. In contrast, biologically sound methods are too detailed and resource-consuming for applications on larger scales. The purpose of this pilot project was to develop an approach that would breach this gap and provide biologically sound rules for environmental flow (eflow) estimation for the region of Poland. The concept was developed using seven river sites, which represent the four of six fish-ecological freshwater body types common in Poland. Each of these types was distinguished based on a specific fish community structure, composed of habitat-use guilds. The environmental significance of the flows for these communities was established with help of the habitat simulation model MesoHABSIM computed for e...
Scaling biodiversity responses to hydrological regimes
Biological reviews of the Cambridge Philosophical Society, 2017
Of all ecosystems, freshwaters support the most dynamic and highly concentrated biodiversity on Earth. These attributes of freshwater biodiversity along with increasing demand for water mean that these systems serve as significant models to understand drivers of global biodiversity change. Freshwater biodiversity changes are often attributed to hydrological alteration by water-resource development and climate change owing to the role of the hydrological regime of rivers, wetlands and floodplains affecting patterns of biodiversity. However, a major gap remains in conceptualising how the hydrological regime determines patterns in biodiversity's multiple spatial components and facets (taxonomic, functional and phylogenetic). We synthesised primary evidence of freshwater biodiversity responses to natural hydrological regimes to determine how distinct ecohydrological mechanisms affect freshwater biodiversity at local, landscape and regional spatial scales. Hydrological connectivity i...
Legacies, lags and long-term trends: Effective flow restoration in a changed and changing world
Freshwater Biology
1. Human impacts on natural ecosystems are pervasive and will play out more severely as human populations and per capita resource use increase. Freshwater ecosystems are critical for human well-being and experience a diverse range of human-induced pressures. Most river systems throughout the world have muchaltered flow regimes. 2. The Murray-Darling Basin in southeastern Australian has been the focus of an extensive water reform process to address the over-allocation of water for human uses. This has included many scientific investigations, hydrological modelling and the development of institutional and market structures to reallocate water. Substantial recovery of water has been achieved, which has been used to restore aspects of the natural flow regime. 3. We reviewed recent papers on responses to flow restoration in the Murray-Darling Basin and complemented this with inferences from the global literature. Ecological responses to flow restoration are often inconsistent, site and taxon specific and difficult to detect. 4. By combining ideas from mainstream thinking in restoration ecology with the insights from our review, we propose a conceptual model for understanding responses to flow restoration. This model incorporates key factors that influence the size of ecological responses to restoration, including existing ecological condition, legacy impacts of past change, interactions with other variables, life-history traits of taxa and broad-scale and long-term trends due to climate or landuse change. K E Y W O R D S antecedent conditions, environmental flows, Murray-Darling Basin, river management 1 | INTRODUCTION The ecological impacts of human actions are pervasive at a global scale, profoundly affecting freshwater ecosystems, which have lost and continue to lose, disproportionately more species than other ecosystems (Ormerod, Dobson, Hildrew, & Townsend, 2010; Strayer & Dudgeon, 2010). Increasing global demands for fresh water for human consumption, agriculture and energy production means that most of the world's large river basins are now substantially degraded ecologically (Nilsson, Reidy, Dynesius, & Revenga, 2005; V€ or€ osmarty et al., 2010). Given the predominance of degraded ecosystems, there is an increasing emphasis on environmental
Freshwater Biology
1. A major outstanding challenge for environmental flow management is to move from a single site, reach or river focus to planning and delivering environmental flows across entire river basins. There is a need for case studies of basin-scale environmental water delivery as a first step in understanding and eventually generalising basin-scale responses. 2. The Commonwealth Environmental Water Holder manages a portfolio of water entitlements for protecting and restoring aquatic ecosystems of the Murray-Darling Basin (MDB). This article describes the strategies used by the water holder and the hydrological outcomes of their basin-scale environmental water delivery program. 3. There are five delivery strategies used to enhance benefits achieved with available environmental water. Although the volume of commonwealth environmental water is small relative to mean catchment inflows, improvements in baseflows and freshes are seen across the MDB. Water was also successfully delivered into floodplain wetlands. 4. The case study provides a successful example of implementing a basin-scale program for environmental water delivery. However, there remains a great need to improve the knowledge, governance and planning tools for managing environmental water for a broad range of ecological demands that operate at the basinscale. K E Y W O R D S environmental flow, flow regime, river basin, river restoration, wetland inundation This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Stakeholder-enhanced environmental flow assessment: The Rufiji Basin case study in Tanzania
River Research and Applications
Environmental flows (E flows) are now a standard part of sustainable water management globally but are only rarely implemented. One reason may be insufficient engagement of stakeholders and their priority outcomes in the E flow-setting process. A recent environmental flow assessment (EFA) in the Kilombero basin of the Rufiji River in Tanzania concentrated on a broad-based investigation of stakeholders' use and perceptions of the ecosystem services provided by the river. The EFA process generally followed the Building Block Methodology but with an enhanced engagement of stakeholders. Engagement began with the involvement of institutional stakeholders to explain the purpose of the EFA and to elicit their priority outcomes. Extensive interactions with direct-use stakeholders followed to investigate their uses of and priorities for the rivers. Results were used by the EFA specialist team in choosing flow indicators and defining measurable environmental objectives. The specialists then met to reach a consensus of the flow requirements. The EFA results were lastly reported back to stakeholders. During the Kilombero EFA we learned that stakeholders at all levels have a good awareness of the natural services provided by a healthy river and can contribute to the setting of environmental objectives for the rivers and floodplain. These can be factored into the biophysical assessments of river flows required to maintain habitats, processes, water quality and biodiversity. It is therefore important to allocate significant resources to stakeholder engagement. It now remains to be seen if enhanced stakeholder engagement, including the increased understanding and capacity built among all stakeholders, will increase support for the implementation of the recommended flows.
Water for the Environment, 2017
Like most environmentally centered disciplines, the field of environmental water management is relatively young. The origins of modern environmental water praxis stem from efforts in the 1970s, mostly to mitigate the impacts of onstream dams by releasing minimum flows to maintain habitat for individual species (Acreman and Dunbar, 2004; Tennant, 1976; Tharme, 2003). Much of the early work was led by water engineers who recognized that hydraulic properties of the river, particularly depth and velocity, were important in defining physical habitat availability for sport fish such as salmon and trout (Bovee and Milhous, 1978; Milhous et al., 1989). This work evolved into the fields of ecohydraulics and ecohydrology. Ecohydraulics extended into microscale processes such as flow turbulence (Wilkes et al., 2013). In a somewhat parallel research stream, ecohydrology saw the growing collaboration between hydrologists and ecologists focused on broader relationships between river flow and ecosystem condition, moving beyond the hydraulic habitat requirements of individual organisms (Dunbar and Creman, 2001; Nestler et al., in review; Chapter 11). The importance of the environmental water regime in sustaining overall ecosystem structure and process became widely accepted in the 1990s (Richter et al., 1997), underscored by the seminal paper of Poff et al. (1997) on the natural flow paradigm, and followed by publication of flowÀecology principles (Bunn and Arthington, 2002; Nilsson and Svedmark, 2002).
Applying Optimization to Support Adaptive Water Management of Rivers
Water, 2021
Adaptive water management is a promising management paradigm for rivers that addresses the uncertainty of decision consequences. However, its implementation into current practice is still a challenge. An optimization assessment can be framed within the adaptive management cycle allowing the definition of environmental flows (e-flows) in a suitable format for decision making. In this study, we demonstrate its suitability to mediate the incorporation of e-flows into diversion management planning, fostering the realization of an adaptive management approach. We used the case study of the Pas River, Northern Spain, as the setting for the optimization of surface water diversion. We considered e-flow requirements for three key river biological groups to reflect conditions that promote ecological conservation. By drawing from hydrological scenarios (i.e., dry, normal, and wet), our assessment showed that the overall target water demand can be met, whereas the daily volume of water availabl...
Ecosystem Services, 2021
Medicine is characterized by its inherent ambiguity, i.e., the difficulty to identify and obtain exact outcomes from available data. Regarding this problem, electronic Health Records (EHRs) aim to avoid imprecisions in the data recording, for instance by its recording in an automatic way or by the integration of data that is both readable by humans and machines. However, the inherent biology and physiological processes introduce a constant epistemic uncertainty, which has a deep implication in the way the condition of the patients is estimated. For instance, for some patients, it is not possible to speak about an exact diagnosis, but about the "suspicion" of a disease, which reveals that the medical practice is often ambiguous. In this work, we report a novel modeling methodology combining explainable models, defined on Logic Neural Networks (LONNs), and Bayesian Networks (BN) that deliver ambiguous outcomes, for instance, medical procedures (Therapy Keys (TK)), depending on the uncertainty of observed data. If epistemic uncertainty is generated from the underlying physiology, the model delivers exact or ambiguous results depending on the individual parameters of each patient. Thus, our model does not aim to assist the customer by providing exact results but is a user-centered solution that informs the customer when a given recommendation, in this case, a therapy, is uncertain and must be carefully evaluated by the customer, implying that the final customer must be a professional who will not fully rely on automatic recommendations. This novel methodology has been tested on a database for patients with heart insufficiency.
Water, 2022
Anthropogenic activities such as damming have caused an alteration in the natural flow regime in many rivers around the world. In this study, the role of constructing a hydroelectric dam on the natural flow regime of the Kor River, Iran, is investigated. Nine different methods, which fall into the category of hydrological methods, were used to determine the environmental water requirement (EWR) of the Kor River. In addition, two indices are introduced to evaluate the environmental flow allocation in anthropogenic rivers. The results show that although the supply of environmental flow in some months is in relatively acceptable conditions on average, there is a deficiency in the allocation of EWR in the range of 1.92–30.2% in the spawning period of the dominant fish species. The proposed indicators can provide a comprehensive picture of the status of environmental flow allocation in rivers where little ecological data is available and the hydrological regime has changed due to human a...
Water, 2020
The threats to small urban streams lead to a decrease in their water quality and dysregulate their ecological balance, thereby affecting the biodiversity and causing degradation of indicators that determine the ecological potential. The aim of our study was to determine the impact of abiotic conditions induced by intensive human activity on the community structures of invertebrates (zooplankton and macroinvertebrates) in the small urban stream Bukówka in the Szczecin agglomeration (NW Poland). This stream exhibits the same characteristics as a large river, in which the mass of live organic matter increases with their length. The composition of invertebrates (zooplankton and macroinvertebrates) was strongly influenced by the changes caused by humans in the stream bed. The construction of small reservoirs and bed regulation in this small urban streams had a similar effect on the quality of the water and ecological potential as in large rivers, but at a lower scale.
Science to support the management of riverine flows
Freshwater Biology, 2018
This is the author manuscript accepted for publication and has undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as
WIREs Water, 2021
Environmental flows (e-flows) are powerful tools for sustaining freshwater biodiversity and ecosystem services, but their widespread implementation faces numerous social, political, and economic barriers. These barriers are amplified in water-limited systems where strong trade-offs exist between human water needs and freshwater ecosystem protection. We synthesize the complex, multidisciplinary challenges that exist in these systems to help identify targeted solutions to accelerate the adoption and implementation of environmental flows initiatives. We present case studies from three water-limited systems in North America and synthesize the major barriers to implementing environmental
Robust Climate Change Adaptation for Environmental Flows in the Goulburn River, Australia
Frontiers in Environmental Science
Climate change presents severe risks for the implementation and success of environmental flows worldwide. Current environmental flow assessments tend to assume climate stationarity, so there is an urgent need for robust environmental flow programs that allow adaptation to changing flow regimes due to climate change. Designing and implementing robust environmental flow programs means ensuring environmental objectives are achieved under a range of uncertain, but plausible climate futures. We apply stress testing concepts previously adopted in water supply management to environmental flows at a catchment scale. We do this by exploring vulnerabilities in different river management metrics for current environmental flow arrangements in the Goulburn River, Australia, under non-stationary climatic conditions. Given the limitations of current environmental flows in supporting ecological outcomes under climate change, we tested three different adaptation options individually and in combinati...
River Research and Applications, 2016
The preservation of instream flows entails multiple benefits not only for river ecosystems but also for human well-being. Benefits of marketed goods and services provided by water withdrawals such as irrigation, water supply and hydropower production are well-known. Others, such as recreational, aesthetic, cultural and existence values of a well-preserved river flows are less studied. There is an increasing interest of policy makers to understand the benefits of costly river ecosystem restoration measures. Moreover, disregarding such benefits may turn into inter-stakeholder conflicts. This paper reviews empirically-based literature assessing environmental flows restoration/conservation. Thus, it offers the state-of-the-art on three aspects: 1) what motivations drive the socioeconomic evaluation of instream flows (policies and alternative instream flow regimes); 2) what values and benefits are associated with instream flows (e.g. the sheer existence of a well-preserved river, productive assets and cultural attributes); and 3) what methods are employed to undertake such assessments (e.g. scenario development, monetary and non-monetary valuations, and stakeholders engagement). Building on this, we propose a methodological framework for case-specific assessments of the restoration of environmental flows. This proposal combines increased stakeholder participation, better understanding of ecosystem functioning, awareness of the plurality of values and an accurate choice of valuation methods.
Sustainability, 2021
Almost a decade ago, the Mexican government targeted to establish environmental water reserves (EWR)—a volume of water allocated for ecological protection based on the Environmental Flow Mexican Norm (eflows, NMX-AA-159-SCFI-2012, ratified in 2017)—in strategic low-pressured for water use and high conservation importance river basins throughout the country. To date, 12 EWRs have been declared for up to 50 years, which encompass 295 river basins and ~55% of the national mean annual runoff (MAR). In this article, we conducted a quality evaluation of the EWRs established. First, the EWR level was analyzed against the MAR and according to wider hydrological conditions. The EWR fulfillment was evaluated by comparing the volumes enacted against the theoretical (Norm implementation). Our findings revealed that independently of individual and regional water use and conservation merits context, ~75% of the EWRs met theoretical volumes at least at an acceptable level, of which medians ranged ...
Designing river flows to improve food security futures in the Lower Mekong Basin
Science (New York, N.Y.), 2017
Rivers provide unrivaled opportunity for clean energy via hydropower, but little is known about the potential impact of dam-building on the food security these rivers provide. In tropical rivers, rainfall drives a periodic flood pulse fueling fish production and delivering nutrition to more than 150 million people worldwide. Hydropower will modulate this flood pulse, thereby threatening food security. We identified variance components of the Mekong River flood pulse that predict yield in one of the largest freshwater fisheries in the world. We used these variance components to design an algorithm for a managed hydrograph to explore future yields. This algorithm mimics attributes of discharge variance that drive fishery yield: prolonged low flows followed by a short flood pulse. Designed flows increased yield by a factor of 3.7 relative to historical hydrology. Managing desired components of discharge variance will lead to greater efficiency in the Lower Mekong Basin food system.
Global change biology, 2018
Novel flow regimes resulting from dam operations and overallocation of freshwater resources are an emerging consequence of global change. Yet, anticipating how freshwater biodiversity will respond to surging flow regime alteration requires overcoming two challenges in environmental flow science: shifting from local to riverscape-level understanding of biodiversity dynamics, and from static to time-varying characterizations of the flow regime. Here, we used time-series methods (wavelets and multivariate autoregressive models) to quantify flow-regime alteration and to link time-varying flow regimes to the dynamics of multiple local communities potentially connected by dispersal (i.e., a metacommunity). We studied the Chattahoochee River below Buford dam (Georgia, U.S.A.), and asked how flow regime alteration by a large hydropower dam may control the long-term functional trajectory of the downstream invertebrate metacommunity. We found that seasonal variation in hydropeaking synchroniz...
Patterns and drivers of fish extirpations in rivers of the American Southwest and Southeast
Global change biology, 2017
Effective conservation of freshwater biodiversity requires spatially explicit investigations of how dams and hydroclimatic alterations among climate regions may interact to drive species to extinction. We investigated how dams and hydroclimatic alterations interact with species ecological and life history traits to influence past extirpation probabilities of native freshwater fishes in the Upper and Lower Colorado River (CR), Alabama-Coosa-Tallapoosa (ACT), and Apalachicola-Chattahoochee-Flint (ACF) basins. Using long-term discharge data for continuously gaged streams and rivers, we quantified streamflow anomalies (i.e., departure "expected" streamflow) at the sub-basin scale over the past half-century. Next, we related extirpation probabilities of native fishes in both regions to streamflow anomalies, river basin characteristics, species traits, and non-native species richness using binomial logistic regression. Sub-basin extirpations in the Southwest (n = 95 Upper CR, n ...
Impacts of small-scale irrigation water use on environmental flow of ungauged rivers in Africa
Environmental Systems Research
Failure in Environmental flow in quantity, timing, and quality leads to failure to support ecosystems, human livelihoods, and well-being. Irrigation water use is one of the main actors in impacting the water flow of rivers in quantity and time but was not well investigated in many ungauged catchments under smallholder irrigation systems. This study examined the impact of irrigation water use on environmental flow in Arata's small ungauged catchment. The study estimated the flow in sub-catchment using the area ratio method, the crop irrigation water requirement using F.A.O. cropwat 8.0, and the water balance in the Water Evaluation and Planning System tool and the environmental flow in Tennants, Q95, asnd local area thumb rule. The result showed that the minimum environmental flow of the Arata catchment is 290, 310, and 60 li/sec in the Tennant, Q95, and the local thumb rule. Irrigation consumes only 9% of the water resources of the catchment while 91% is contributed to downstrea...
Water Availability for the Environmental Flow in Two Rivers of Mexico under Climate Change
IntechOpen eBooks, 2022
Adaptation to climate change requires, among others, the modification of river flow regimes to account for the change in household, agricultural, industry, and energy water consumption as well as their short/medium/long-term socioeconomic impact. In this study, the comparative analysis of the variation of the precipitation in relation to the availability of water in the Yautepec and Cuautla rivers in Morelos, Mexico, for the previous period and subsequent period is carried out, to determine the change in the availability of water in the ecosystem. In winter (February), an increase in rainfall on the Yautepec and Cuautla River was observed, where annual seasonal agriculture and Pine and Oyamel forest are the characteristic vegetation. In autumn (October), a decrease in precipitation takes place. The flows in some regions do not coincide with the increase in the percentage of precipitation (Oaxtepec and Las Estacas Stations) and point out the synergistic effect of the human use of the water resource and the effects of climate change. On Ticumán Station, the depletion of the flow only can be associated with the use of the resource by human influence. The modifications caused by alteration of a river's flow regime and climatic change must be studied through comparative multidisciplinary studies that give to decision-makers the design of environmental flows.
Replenishing the Indus Delta through multi-sector transformation
Frontiers in Environmental Science
The Indus River Basin (IRB) is a severely water-stressed and rapidly developing home to an estimated 250 million people in South Asia. An acute deficit of environmental flows (EFs) in the basin’s delta negatively impacts geomorphology and surrounding ecosystems. Here, a sub-national model of the IRB’s integrated water–energy–land systems is applied to quantify multi-sector transformations and system costs for enhancing EFs to the Indus Delta. The results show that increasing the average outflows from the basin relative to historical policy levels by 2.5 and 5 times would increase sectoral costs for upstream water users between 17–32 and 68–72% for low and high ecological potential targets. The enhanced EFs result in more energy for pumping and treating water upstream from the delta and a net increase in irrigation and energy investments. The EF policy costs are minimized by 7–14% through cooperation across countries and 6–9% through the coordinated implementation of water efficiency...
We Have Eaten the Rivers: The Past, Present, and Unsustainable Future of Hydroelectricity in Vietnam
Sustainability
Vietnam has one of the most intensively energy-exploited riverscapes in Asia with at least 720 hydropower facilities of various capacities currently in operation or in some stage of construction. These facilities represent about 26 GW of installed capacity. This degree of domestic exploitation is often overshadowed by the geopolitically contested manipulation of the waters of the international Mekong River. In contrast, the utilization of Vietnam’s hydropower resources has unfolded gradually and largely unremarked for more than half a century. This perspective argues that the harnessing of rivers and streams for electricity generation is the result of not only the country’s abundant hydrologic resources, but also its history, culture, and (geo)politics. The paper traces the processes that have produced this high level of river exploitation, its ambiguous history, and the uncertain future of hydropower in Vietnam in the context of sustainability. Further, the renewed interest in dam-...
Journal of Geophysical Research: Earth Surface, 2018
Field observations, experiments, and numerical simulations suggest that pool-riffles along gravel bed mountain streams develop due to downstream variations of channel width. Where channels narrow, pools are observed, and at locations of widening, riffles occur. Based on previous work, we hypothesize that the bed profile is coupled to downstream width variations through momentum fluxes imparted to the channel surface, which scale with downstream changes of flow velocity. We address this hypothesis with flume experiments understood through scaling theory. Our experiments produce pool-riffle like structures across average Shields stresses * that are a factor 1.5-2 above the threshold mobility condition of the experimental grain size distribution. Local topographic responses are coupled to channel width changes, which drive flows to accelerate or decelerate on average, for narrowing and widening, respectively. We develop theory which explains the topography-width-velocity coupling as a ratio of two reinforcing timescales. The first timescale captures the time necessary to do work to the channel bed. The second timescale characterizes the relative time magnitude of momentum transfer from the flowing fluid to the channel bed surface. Riffle-like structures develop where the work and momentum timescales are relatively large, and pools form where the two timescales are relatively small. We show that this result helps to explain local channel bed slopes along pool-riffles for five data sets representing experimental, numerical, and natural cases, which span 2 orders of magnitude of reach-averaged slope. Additional model testing is warranted. Plain Language Summary Mountain streams commonly display a riverbed shape that has a repetitive pattern of topographic lows and highs known respectively as pools and riffles. Visually, pools appear as relatively deep portions of a river, with slow water velocities, and riffles appear as comparatively shallow portions, with more rapid water velocities. Pool-riffles are ecologically important because salmon rely on them for birth, growth, and regeneration, and they are physically important because pool-riffles are observed across diverse landscape settings. Despite their importance, the scientific community lacks a clear explanation for pool-riffle formation. This research shows that pool-riffles develop in response to how channel width and water velocity change moving in the downstream direction. When channels narrow, pools form due to higher water velocities. When channels widen, riffles form due to lower water velocities. We demonstrate our finding with a mathematical model motivated by experimental observations and built using a combination of theory and physical scaling. The model reasonably describes pool-riffle bed topography for five different studies, representing a wide range of experimental, numerical, and natural conditions. The model can be used to test pool-riffle formation under differing conditions, and practitioners will find it useful for river restoration design purposes.
Débits écologiques : la place des modèles d’habitat hydraulique dans une démarche intégrée
Hydroécologie Appliquée, 2016
Deux types d’approches techniques complémentaires sont utilisées pour guider l’établissement des débits écologiques, à l’échelle des tronçons de cours d’eau (ex. : débits réservés) comme à l’échelle de bassins versants (ex. : débits objectifs d’étiage). Les approches « hydrologiques » visent à quantifier les altérations de multiples caractéristiques du régime hydrologique et reposent sur l’identification (délicate) de relations empiriques entre altérations hydrologiques et biologiques. Les approches « habitat hydraulique », ciblées sur les débits bas à moyens, couplent des modèles hydrauliques et des modèles biologiques pour traduire certaines modifications hydrologiques en modification de qualité de l’habitat hydraulique pour les organismes. Elles ont parfois apporté des prédictions convaincantes des effets biologiques des modifications de débits d’étiage. Ces deux approches techniques ne fournissent pas directement de valeurs de débits écologiques. Nous formalisons ici une démarch...
Consistent but secondary influence of hydropeaking on stream fish assemblages in space and time
Journal of ecohydraulics, 2020
Hydropeaking corresponds to rapid artificial discharge variations, designed to address subdaily peaks in electricity demand. It generates rapid changes in physical habitat (e.g., flow velocity and water depth) with potential impacts on stream assemblages. For assessing the generality of hydropeaking effects on fish assemblages, we present an original combination of spatial (among 45 reaches, including six groups of nearby reaches) and temporal (over 3-17 years) analyses of these effects. Our analyses involved descriptions of natural and artificial hydraulic variations in reaches, obtained after translating hourly discharge data into hydraulics. We found that the influence of hydropeaking was secondary compared to well-known spatial variations in fish assemblage structure along longitudinal gradients, and negative influences of floods on annual densities. However, the spatial and temporal analyses consistently suggested that hydropeaking may disfavour fish species typical of medium-sized streams relative to species of headwater streams (Salmo trutta, Phoxinus phoxinus, Cottus gobio). The magnitude of hydropeaking effects observed here, as well as an apparent weaker effect of ramping rates than the frequency of hydropeaks, may be due to lower ramping rates in our data set than in other studies.
Geochemical signatures of acidic drainage recorded in estuarine sediments after an extreme drought
Science of The Total Environment, 2020
• Extreme drought triggered extensive acid sulfate soil oxidation and acidification. • Acidic drainage mobilised major, trace and rare earth metals into the estuary. • This caused localised and lake-wide enrichment of metals in recent sediments. • Sediment transport processes shaped metal transport and deposition. • Estuary geomorphology contributed to the intensity of metal release.
Fishes in a changing world: learning from the past to promote sustainability of fish populations
Journal of Fish Biology, 2018
Populations of fishes provide valuable services for billions of people, but face diverse and interacting threats that jeopardize their sustainability. Human population growth and intensifying resource use for food, water, energy and goods are compromising fish populations through a variety of mechanisms, including overfishing, habitat degradation and declines in water quality. The important challenges raised by these issues have been recognized and have led to considerable advances over past decades in managing and mitigating threats to fishes worldwide. In this review, we identify the major threats faced by fish populations alongside recent advances that are helping to address these issues. There are very significant efforts worldwide directed towards ensuring a sustainable future for the world's fishes and fisheries and those who rely on them. Although considerable challenges remain, by drawing attention to successful mitigation of threats to fish and fisheries we hope to prov...
Common carp (Cyprinus carpio; hereafter carp) is a highly invasive freshwater fish that has colonised river basins across the world causing ecological degradation. In regulated rivers, restoration of natural flow regimes to rehabilitate aquatic ecosystems is a primary focus of environmental management, yet some actions (e.g., environmental water delivery or artificial floodplain inundations) may have unintended consequences including favouring carp. We developed a stochastic population model to represent carp population responses to hydrology and management actions. The model uses current understanding of carp life history, including different survival rates of early life-stages for a range of habitat types, to estimate population responses to various flow/inundation scenarios. Using case studies from two major regions of a large, regulated dryland river, we demonstrate that large natural floods and prolonged droughts accounted for the greatest amplitude of projected carp population...
Ecological Indicators
Holistic environmental flows frameworks are built on our understanding of key flow-ecology relationships that support sensitive taxa and critical ecosystem functions under different flow and water level scenarios. Most research on flow-ecology relationships has typically focused on small systems, with less known about flow associations, indicator taxa, and environmental thresholds of assemblage change along hydraulic gradients of large non-wadeable rivers. We assessed benthic macroinvertebrate assemblage structure and applied Taxa Indicator Threshold ANalysis (TITAN) on biomonitoring data collected during a six-year period in the Wolastoq | Saint John River in Atlantic Canada. Flow velocity was strongly associated with the distribution and relative abundance of benthic macroinvertebrates in the river, and taxon associations reflected functional adaptations to flow. We identified 33 genus-level indicator taxa that were either positively or negatively associated with flow velocity. Weaker taxa responses were shown for the gradient in median substrate particle size where 22 negatively and positively responding taxa were identified. We predicted changes in indicator taxon abundance under different flow scenarios using a hydrodynamic model, and characterised the distribution and availability of suitable hydraulic habitat patches within a 20 km reach downstream of a large hydropower generating station. These observations set the stage for the development of ecologically-based flow targets to support holistic environmental flow management in large rivers.
Time for decisive actions to protect freshwater ecosystems from global changes
Knowledge & Management of Aquatic Ecosystems
Freshwater ecosystems and their biodiversity provide fundamental services to humans such as nutritional resources production, water provisioning, water purification, recreation, and more globally climate regulation. Anthropogenic impacts on freshwater ecosystems and their biodiversity are already strong and will most probably increase in the near future. Anthropogenic drivers are widely known and include in particular, climate change, habitat shrinking and/or modification due to land-use (e.g. water abstraction for human and agricultural consumption, urbanization), habitat fragmentation and homogenization in stream flow dynamics due to the damming of rivers, introduction of non-native species, dumping of nutrient or organic loadings increasing eutrophication processes, and biodiversity over-exploitation. Here, I review the current and future effects of these anthropogenic drivers on freshwater ecosystems and their biodiversity and provide some few examples of existing solutions, eit...
Ecosphere, 2019
The long‐term management of aridland riparian ecosystems impacted by dams is crucial to reduce losses of biodiversity, reduce extinction risks for species, and restore ecosystem services. When dams preclude natural flow, safeguarding aridland riparian ecosystems adapted to infrequent, catastrophic floods poses additional challenges owing to the need to consider biological and pattern legacies. Seven Oaks Dam (California, USA) eliminated the occurrence of flooding, scouring, and deposition across the rare plant community downstream. This Riversidian alluvial fan sage scrub or alluvial scrub includes one of the most endangered plants in California, Eriastrum densifolium spp. sanctorum (Santa Ana River woolly star, hereafter called woolly star). In this study, we evaluated the impact of six soil geomorphic treatments on alluvial scrub and woolly star re‐establishment after 5, 7.5, and 13 yr. We implemented a complete randomized block design, with each block incorporating six treatments...
Ecohydrology, 2020
Rivers are among the most altered environments globally but identifying which threats are responsible for observed biotic and abiotic changes is complicated by natural drivers of variation. The Bow River, Canada provides an ideal model to resolve these influences and explore spatial relationships. It originates from pristine Rocky Mountain headwaters and is subsequently impacted by typical human alterations: damming, municipal channelization and effluent release, and agricultural impacts (nutrient enrichment, water withdrawal for irrigation). By coordinating studies of the Bow River's biota, we demonstrate how threat-driver interactions depend on season and the abiotic factor and biotic community or species of interest. We conclude that impact severity and riverine recovery depend on the threat magnitude, its longitudinal position and proximity to other threats and natural drivers. We found that river regulation, water extraction and bank armouring interact to limit geomorphic processes resulting in depleted riparian woodlands and numbers of fish species, though a large, undammed tributary nearby allows quick recovery downstream. We highlight the implications of the longitudinal position of the threats since cold-water fish species are disproportionately impacted through the area where the human impacts on the Bow River overlap. We illustrate how the interactions between flow, nutrients and temperature lead to macrophyte or algae dominated communities and associated shifts in fish composition and biomass. Finally, we applied our increased understanding of ecological riverine processes to conclude that management techniques such as flushing flows or functional environmental flows are likely to have only minimal or conditional success in the Bow River.