Papers by Michael Stewardson
Frontiers in Environmental Science, 2018
Environmental flows are a critical tool for addressing ecological degradation of river systems br... more Environmental flows are a critical tool for addressing ecological degradation of river systems brought about by increasing demand for limited water resources. The importance of basin scale management of environmental flows has long been recognized as necessary if managers are to achieve social, economic, and environmental objectives. The challenges in managing environmental flows are now emerging and include the time taken for changes to become manifest, uncertainty around large-scale responses to environmental flows and that most interventions take place at smaller scales. The purpose of this paper is to describe how conceptual models can be used to inform the development, and subsequent evaluation of ecological objectives for environmental flows at the basin scale. Objective setting is the key initial step in environmental flow planning and subsequently provides a foundation for effective adaptive management. We use the implementation of the Basin Plan in Australia's Murray-Darling Basin (MDB) as an example of the role of conceptual models in the development of environmental flow objectives and subsequent development of intervention monitoring and evaluation, key steps in the adaptive management of environmental flows. The implementation of the Basin Plan was based on the best science available at the time, however, this was focused on ecosystem responses to environmental flows. The monitoring has started to reveal that limitations in our conceptualization of the basin may reduce the likelihood of achieving of basin scale objectives. One of the strengths of the Basin Plan approach was that it included multiple conceptual models informing environmental flow management. The experience in the MDB suggests that the development of multiple conceptual models at the basin scale will help increase the likelihood that basin-scale objectives will be achieved.
Frontiers in Ecology and the Environment, 2014
W ater management has historically focused on direct resource benefits (eg for domestic use, grow... more W ater management has historically focused on direct resource benefits (eg for domestic use, growing food, generating power, supporting industry) to people through economic growth or poverty alleviation. Nevertheless, many global initiatives (eg MA 2005) have highlighted the link between biodiversity, ecosystems, and human well-being. Thus, providing water for the CONCEPTS AND QUESTIONS
The book first provides a summary of the Murray-Darling River system: its hydrology, water-relate... more The book first provides a summary of the Murray-Darling River system: its hydrology, water-related ecological assets, land uses (particularly irrigation), and its rural and regional communities; and management within the Basin, including catchments and natural resources, water resources, irrigation, environment, and monitoring and evaluation. Additionally, the recent major water reforms in the Basin are discussed, with a focus particularly on the development and implementation of the Basin Plan.Murray-Darling Basin, Australia: Its Future Management then provides an analysis of the next set of policy and institutional reforms (environmental, social, cultural and economic) needed to ensure the Basin is managed as an integrated system (including its water resources, catchment and estuary) capable of adapting to future changes. Six major challenges facing the Basin are identified and discussed, particularly within the context of predicted changes to the climate leading to an increased f...
Frontiers in Environmental Science
Climate change presents severe risks for the implementation and success of environmental flows wo... more 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, 2014
Around the world, governments are making huge investments in environmental flows. However, much o... more Around the world, governments are making huge investments in environmental flows. However, much of the rationale for these releases is based on expert opinion and is thus open to challenge. Empirical studies that relate ecological responses to flow restoration are mostly case studies of limited generality. Radically, different approaches are required to inform the development of general models that will allow us to predict the effects of environmental flows. Here, we describe the modelling framework being used in a major study of environmental flows in the Australian state of Victoria. The framework attempts to make best use of all the information available from the literature, experts, and monitoring data, to inform the development of general quantitative response models. It uses systematic review of the literature to develop evidence-based conceptual models, formal expert elicitation to provide an initial quantification of model links, and data derived from purpose-designed monitoring programs over large spatial scales. These elements come together in a Bayesian hierarchical model that quantifies the relationship between flow variation and ecological response and hence can be used to predict ecological responses to flow restoration. We illustrate the framework using the example of terrestrial vegetation encroachment into regulated river channels. Our modelling framework aims to develop general flowresponse models and can immediately be used to demonstrate the ecological return on investment from environmental flow programs. However, the framework also has the potential to be incorporated into planning and decision-making processes, helping to drive a transformation in evidence-based practice for environmental flow management.
Key Points • We reviewed the impact of dams on floodplain geomorphology, using a traditional lite... more Key Points • We reviewed the impact of dams on floodplain geomorphology, using a traditional literature review and a systematic review using 'causal criteria' analysis • We distinguish between 'passive impacts' (floodplain disconnection) and 'active impacts' (changes in geomorphological processes and functioning) • Potential impacts include changes to: overbank flooding, scour and sedimentation, within-channel bank erosion, meander migration and cutoff frequency, and avulsion characteristics and frequency • The causal criteria analysis found that, with the exception of reduced meander migration rates, most impacts have been too poorly documented to be confident in their impact at present • Given practical constraints, options to mitigate dam impacts during their operational lifetime are limited to using within-channel flows to maintain meander migration and partial floodplain connectivity. We suggest that the major restoration action should be to ensure that ...
ABSTRACT In a world of increasing water scarcity, environmental flows programs need to be underpi... more ABSTRACT In a world of increasing water scarcity, environmental flows programs need to be underpinned by robust quantitative predictions of the ecological benefits expected to result from returning water to the environment. However, many environmental flow recommendations have been qualitative and based upon expert opinion. We developed a process designed to make maximal use of all the information that can be brought to bear on the problem of modelling ecological responses to flow variation. It employs literature analysis, expert elicitation, and Bayesian hierarchical analysis of data from purpose-built monitoring programs. The process has been implemented through research associated with the Victorian Environmental Flows Monitoring and Assessment Program, in the Australian state of Victoria. While proving very successful in the derivation of general flow-response relationships that can be used in future to predict the ecological benefits of environmental flows programs, we encountered unforeseen difficulties with implementing the process within a science-management partnership. Our experience may assist future users to implement similar approaches successfully elsewhere in the world.
Environmental Modelling & Software, 2015
We describe software to facilitate systematic reviews in environmental science. Eco Evidence allo... more We describe software to facilitate systematic reviews in environmental science. Eco Evidence allows reviewers to draw strong conclusions from a collection of individually-weak studies. It consists of two components. An online database stores and shares the atomized findings of previously-published research. A desktop analysis tool synthesizes this evidence to test causeeeffect hypotheses. The software produces a standardized report, maximizing transparency and repeatability. We illustrate evidence extraction and synthesis. Environmental research is hampered by the complexity of natural environments, and difficulty with performing experiments in such systems. Under these constraints, systematic syntheses of the rapidly-expanding literature can advance ecological understanding, inform environmental management, and identify knowledge gaps and priorities for future research. Eco Evidence, and in particular its online re-usable bank of evidence, reduces the workload involved in systematic reviews. This is the first systematic review software for environmental science, and opens the way for increased uptake of this powerful approach.
Water Science & Technology, 2014
Raingardens are becoming an increasingly popular technology for urban stormwater treatment. Howev... more Raingardens are becoming an increasingly popular technology for urban stormwater treatment. However, their hydraulic performance is known to reduce due to clogging from deposition of fine-grained sediments on the surface. This impacts on their capacity to treat urban runoff. It has been recently hypothesised that plants can help to mitigate the effect of surface clogging on infiltration. A conceptual model is therefore presented to better understand key processes, including those associated with plant cover, which influences surface infiltration mechanisms. Based on this understanding, a field evaluation was carried out to test the hypothesis that plants increase the infiltration rate, and to investigate factors that influence the deposition of fine-grained sediments within raingardens. The results show that infiltration rates around plants are statistically higher than bare areas, irrespective of the degree of surface clogging. This suggests that preferential flow pathways exist ar...
International Journal of River Basin Management, 2014
ABSTRACT Environmental flows programmes can be controversial, given that they transfer water from... more ABSTRACT Environmental flows programmes can be controversial, given that they transfer water from consumptive to environmental uses. It is, therefore, imperative that their performance is assessed against their anticipated ecological benefits. However, environmental flows present both technical and institutional challenges that cannot be addressed by traditional approaches to monitoring and evaluation. We present a framework that is currently being employed to evaluate the effectiveness of environmental flows in Victoria, Australia. The framework encourages a shift from expert-based models of ecological response to flow variation to those developed using the so-called ‘evidence-based’ methods that have become commonplace in medicine. The framework relies on close collaboration between scientists and managers for the design of monitoring programmes, collection and collation of data, and analysis and interpretation of results. Results will inform adaptive management of environmental flows in Victoria and improve basic understanding of the ecological impacts of changes in flow regime. Our experience suggests that the technical and institutional challenges for monitoring and evaluating environmental flows can be mostly overcome by close and continuing collaboration between managers and researchers. We are unaware of any equivalent programmes anywhere in the world and believe that our framework is transferable to any other large-scale environmental flows monitoring programme.
Geomorphology, 2014
Urbanization almost inevitably results in changes to stream morphology. Understanding the mechani... more Urbanization almost inevitably results in changes to stream morphology. Understanding the mechanisms for such impacts is a prerequisite to minimizing stream degradation and achieving restoration goals. However, investigations of urban-induced changes to stream morphology typically use indicators of watershed urbanization that may not adequately represent degrading mechanisms and commonly focus on geomorphic attributes such as channel dimensions that may be of little significance to the ecological goals for restoration. We address these shortcomings by testing if a measure characterizing urban stormwater drainage system connections to streams (effective imperviousness, EI) is a better predictor of change to ecologically relevant geomorphic attributes than a more general measure of urban density (total imperviousness, TI). We test this for 17 sites in independent watersheds across a gradient of urbanization. We found that EI was a better predictor of all geomorphic variables tested than was TI. Bank instability was positively correlated with EI, while width/depth (a measure of channel incision), bedload sediment depth, and frequency of bars, benches, and large wood were negatively correlated. Large changes in all geomorphic variables were detected at very low levels of EI (b 2-3%). Excess urban stormwater runoff, as represented by EI, drives geomorphic change in urban streams, highlighting the dominant role of the stormwater drainage system in efficiently transferring stormwater runoff from impervious surfaces to the stream, as found for ecological indicators. It is likely that geomorphic condition of streams in urbanizing watersheds, particularly those attributes of ecological relevance, can only be maintained if excess urban stormwater flows are kept out of streams through retention and harvesting. The extent to which EI can be reduced within urban and urbanizing watersheds, through techniques such as distributed stormwater harvesting and infiltration, and the components of the hydrologic regime to be addressed, requires further investigation.
Freshwater Biology, 2013
1. Human-induced changes in river flow regimes are ubiquitous worldwide. Although numerous case s... more 1. Human-induced changes in river flow regimes are ubiquitous worldwide. Although numerous case studies have identified negative ecological impacts of changes in different aspects of flow regimes (e.g. magnitude, timing), there have been few attempts to systematically review this literature to derive general relationships regarding ecological responses to changes in flow regimes. 2. Systematic literature reviews can inform science and management in ecologically complex systems not amenable to experimentation. However, such analysis of existing literature is often limited by inconsistent study design and data reporting. To attempt to overcome these difficulties, we used the recently developed Eco Evidence method and software to analyse 165 studies of ecological responses to changes in river flow regimes. 3. Eco Evidence provides a rule set and standardised list of terms to assist reviewers to interpret consistently the results of disparate studies. The companion software assists with the synthesis of this information to reach transparent and repeatable conclusions regarding cause-effect hypotheses of ecological responses to environmental drivers. 4. We compared our results to those of a recent, informal systematic review of the same studies, which is proving extremely influential. Stronger conclusions are reached when evidence is weighted, classified and combined according to the rules in Eco Evidence. Compared to the original review, we reached informative conclusions for a larger number of flow-response hypotheses, found that hypotheses for which the most evidence was available returned inconsistent results, addressed hypotheses at levels of conceptual resolution relevant to management and identified where insufficient evidence exists to reach a conclusion. 5. Analyses conducted at several levels of conceptual resolution found strong support for many hypotheses regarding ecological impacts. We found a consistent sensitivity to changes in flow regime for both fish and riparian vegetation across a variety of performance metrics. While macroinvertebrate responses varied among performance metrics (e.g. abundance was negatively affected by increases or decreases in flows, diversity was only negatively affected by flow decreases, and assemblage structure was affected by neither), they were largely consistent within these metrics. 6. We thus conclude that the Eco Evidence approach allowed us to extract more knowledge from the data set than was possible in the original review. Eco Evidence can improve synthesis of the burgeoning ecological literature and improve our general understanding in ecology. Amid widespread
Environmental Management, 2013
Encroachment of riparian vegetation into regulated river channels exerts control over fluvial pro... more Encroachment of riparian vegetation into regulated river channels exerts control over fluvial processes, channel morphology, and aquatic ecology. Reducing encroachment of terrestrial vegetation is an oft-cited objective of environmental flow recommendations, but there has been no systematic assessment of the evidence for and against the widely-accepted cause-and-effect mechanisms involved. We systematically reviewed the literature to test whether environmental flows can reduce the encroachment of terrestrial vegetation into river channels. We quantified the level of support for five explicit causeeffect hypotheses drawn from a conceptual model of the effects of flow on vegetation. We found that greater inundation, variously expressed as changes in the area, depth, duration, frequency, seasonality, and volume of surface water, generally reduces riparian vegetation abundance in channels, but most studies did not investigate the specific mechanisms causing these changes. Those that did show that increased inundation results in increased mortality, but also increased germination. The evidence was insufficient to determine whether increased inundation decreases reproduction. Our results contribute to hydroecological understanding by using the published literature to test for general cause-effect relationships between flow regime and terrestrial vegetation encroachment. Reviews of this nature provide robust support for flow management, and are more defensible than expert judgement-based approaches. Overall, we predict that restoration of more natural flow regimes will reduce encroachment of terrestrial vegetation into regulated river channels, partly through increased mortality. Conversely, infrequent deliveries of environmental flows may actually increase germination and subsequent encroachment.
Australian Journal of Water Resources, 2013
ABSTRACT Effectively transferring complex scientific ideas into the policy domain is a serious ch... more ABSTRACT Effectively transferring complex scientific ideas into the policy domain is a serious challenge, but an essential one given the important role of science in assessing the implications of a changing climate and resulting water shortages in Australia. Eco Evidence, a method for conducting systematic reviews of the scientific literature using causal criteria analysis, was developed for the eWater Cooperative Research Centre to help bridge this gap between science and policy. It provides a transparent and repeatable method for assessing the strength of the available scientific evidence regarding particular management actions. However, if evidence is used to justify decisions rather than to provide options and likely outcomes of these options to stakeholders, its effectiveness can be undermined. By drawing on interdisciplinary theories of uncertainty in the science-policy arena, this paper demonstrates how Eco Evidence can be used in evidence-based practice in a manner that does not interfere with the effective participation of a range of stakeholders in the decision-making process.
... software product is designed to facilitate extraction and sharing of ecological evidence, and... more ... software product is designed to facilitate extraction and sharing of ecological evidence, and also provides a standardised method for weighting and combining evidence to develop arguments for causality (Norris et al. 2008, Wealands et al. 2009). ... Wealands et al. ...
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Papers by Michael Stewardson