Michael J. Stewardson

• PhD
• Environmental Hydrology and Water Resources at University of Melbourne

Across the globe, environmental water has been allocated with the purpose of preserving the health and vitality of floodplain vegetation. However, the influences of environmental water volume and environmental water delivery strategies have not been studied widely because of shortage of on‐ground monitoring data. Remotely sensed data can bridge thi...

Future water availability is threatened by changes in both climate and water demand. Water rights with differing priorities are an important foundation of demand‐side tools (e.g., buyback, water pricing, and water market) to improve water use efficiency and reduce water scarcity, especially in highly regulated river systems. This paper assesses the...

Protecting freshwater systems to ensure sustainability requires diagnosing threats over a broad range of scales, from local to global. There is growing acceptance that environmental flows must be protected to sustain river channels and floodplain ecosystems downstream of reservoirs. Meeting environmental water requirements has proven difficult beca...

Fine particle clogging and faunal bioturbation are two key processes co‐occurring in the hyporheic zone that potentially affect hyporheic exchange through modifications in the sediment structure of streambeds. Clogging results from excessive fine sediment infiltration and deposition in rivers, and it is known to decrease matrix porosity and potenti...

Simple analytical storage–reliability–yield relationships have traditionally only considered a single reliability for a single yield, yet many reservoirs supply water of different priorities. Simulation models may be used to handle such multiple‐priority water rights but these models are complex and usually system specific. Here we propose a simple...

Models of populations in habitat networks are vital for understanding and linking processes and patterns across individuals, environments, ecological interactions, and population structures. River ecosystem models combine the physical structure of the networks with the biological processes of the organisms using structural and functional models, re...

Understanding long-term trends in streamflow is important for water resource management. In this study, we investigate the long-term streamflow trends at 47 gauging sites within the southern Murray-Darling Basin (MDB), Australia. This study aims to estimate regional streamflow trends while understanding the impact of catchment characteristics on th...

Climate change is projected to impact multiple components of the flow regime. However, changes in some ecologically important aspects of flow seasonality and variability are not well‐represented by global climate models. We used a stress testing method and global sensitivity analysis to investigate whether interactions between five different, but p...

River floodplains are among the most dynamic and diverse ecosystems on the planet. They are at risk of degradation due to river regulation and climate change. Environmental water has been delivered to floodplains to maintain environmental health by mimicking natural floods. It is important to understand the long-term effects of environmental water...

In the face of mounting environmental and political challenges in river management, accurate and timely scientific information is required to inform policy development and guide effective management of waterways. The Murray–Darling Basin is Australia's largest river system by area and is the subject of a heavily contested series of water reforms re...

The mobilization and mixing of sediments by the activities of in-stream fauna, referred to as sediment reworking, constantly modifies the hydro-physical properties of streambeds. This sediment-organism interaction has been increasingly recognized to influence the hyporheic exchange flows in stream ecosystems, particularly in low flow environments (...

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 robus...

Water supply authorities (WSAs) can influence the behaviour of water users and are influential actors in water governance. Despite this, their decision-making processes and the details of their interactions with other water users are seldom explored empirically in water management research. We undertook an exploratory qualitative study using semi-s...

Many water scientists aim for their work to inform water policy and management, and in pursuit of this objective, they often work alongside government water agencies to ensure their research is relevant, timely and communicated effectively. A paper in this issue, examining 'Science integrity, public policy and water governance in the Murray-Darling...

Streambed inhabitants mix and mobilize sediments by actions such as burrowing, feeding, and excretion, a process referred to as sediment reworking. This sediment-organism interaction could modify the hydro-physical properties of streambeds and significantly influence the hyporheic flow regime in streams as highlighted by our recent research. In thi...

In the face of mounting environmental problems, it is essential that accurate and timely scientific information is available to inform policy development and guide management. Scientists have specialised knowledge necessary for evidenced-based decision making, but despite extensive literature on the interface between science and policy, there is li...

Daily timescale hydrological information is important for many purposes such as flood estimation, predicting the consequences of catchment management and meeting the needs of freshwater ecology. In hydrological assessments, daily timestep modelling is typically used because of the availability of daily data and many of the processes governing impac...

This work demonstrates how the sediment-organism contact time influences the degree to which hyporheic flow regime is modified.

In-stream faunal organisms constantly interact with their habitat to modify its physical and hydraulic properties. However, little is known about how sediment-organism interactions could modify the hyporheic exchange. Previous experimental work investigating the effects of the activities of faunal organisms on exchange across the sediment-water int...

Bioturbation occurs in streambeds by the action of a range of faunal species, but little is known about how it could modify the hyporheic exchange in streams. Previous experimental work investigating the effects of sediment‐biota interaction on exchange across the sediment‐water interface has been largely conducted in small mesocosms or infiltratio...

Riffle-pool sequences are fundamental, ubiquitous morphological features of alluvial rivers that are thoroughly studied in general and commonly incorporated into river restoration projects. Most previous investigations on the effect of riffle-pool sequences on hyporheic exchanges focused on solely bed undulation, because that is widely thought to b...

This chapter provides a holistic view of the hydrology of the Murray–Darling Basin (MDB) within which local hydrological systems and issues can be contextualised. Surprisingly, despite many decades of hydrological research, this is the first time the hydrology of the whole Basin has been described, including its natural hydrological connectivity, t...

This chapter provides a brief introduction to the Murray–Darling Basin system. This chapter overviews the Australian system of government, the Murray–Darling Basin system (water resources, land use, economy, rural communities, and environment), the water reforms in the Basin over the past 30 years including the Water Act 2007 and the Basin Plan 201...

The major water resource policy and management reforms that have occurred in Australia's Murray–Darling Basin (MDB) over the past 30 years have made a good start to ensuring the MDB is a healthy and sustainable working Basin into the future. This is particularly true of the Basin Plan and the $A13 billion being invested to recover water for the env...

In this work, the deposition of clay‐sized fine particles (d50 = 0.006 mm) and its subsequent influence on the dune‐induced hyporheic exchange are investigated. Fine sand (D50 = 0.28 mm), coarse sand (D50 = 1.7 mm), and gravel (D50 = 5.5 mm) grains were used to form homogenous model streambeds; one control ‐ no clay input, and two treatments ‐ incr...

Many freshwater ecosystems are in decline because of anthropogenic disturbance including climate change, yet our understanding of ecological vulnerability to future conditions including climatic variation is limited. Understanding climate risks to freshwater ecosystems requires combining hydrological and ecological knowledge. While there have been...

Algal pollution in water sources has posed a serious problem. Estimating algal concentration in advance saves time for drinking water plants to take measures and helps us to understand causal chains of algal dynamics. This paper explores the possibility of building a short-term algal early warning model with online monitoring systems. In this study...

The permeability of sediments at the sediment–water interface is an important control on several stream ecosystem services. It is well known that streambed permeability varies over several orders of magnitude, however, the environmental processes influencing this variation have received little attention. This review synthesizes the state-of-art kno...

Donwload one of the 50 free eprints here: https://www.tandfonline.com/eprint/C4B3NQVBGVH7HSGSRXTP/full?target=10.1080/24705357.2020.1813057 Interdisciplinary approaches are required to tackle complex environmental issues as freshwater ecosystems face unprecedented pressures globally. The emerging Ecohydraulics field of research should, therefore,...

Riverine ecosystems provide important ecosystem services reflecting their unique forms and functions. While the effects of stressors such as land cover change, climate change and growing economies on riverine ecosystem services (RES) have been well researched, the effect of the structure of the river network itself is less understood. This paper co...

The forecast of warmer weather, and reduced precipitation and streamflow under climate change makes freshwater biota particularly vulnerable to being exposed to temperature extremes. Given the importance of temperature to regulate vital physiological processes, the availability of discrete cold-water patches (CWPs) in rivers to act as potential the...

Environmental water represents a key resource in managing freshwater ecosystems against pervasive threats. The impacts of climate change add further pressures to environmental water management, yet anticipating these impacts through modelling approaches remains challenging due to the complexities of the climate, hydrological and ecological systems....

The Murray–Darling Basin in south‐eastern Australia contains over 70,000 km2 of wetlands and floodplains, many of which are in poor condition. In response, Australian governments have committed to a major restoration program, the Murray–Darling Basin Plan that includes management of 2,750 Gl of environmental water to protect and restore aquatic eco...

The contribution of agriculture to society is undeniable, as is its impact on the environment. Irrigators' decisions to follow best management practices or implement a policy change, to accept a technology, or even to exit farming, all affect society. Hence the decision‐making behavior of irrigators is of interest to politicians, policymakers, and...

High flow pulses (or spells or freshes) play a crucial role in maintaining the ecological health of a river system. Impoundment of water in a reservoir and release or diversion of water for human water needs has significantly altered the magnitude and frequency of flow pulses in many river systems, often reducing river ecological health. A limited...

High flow pulses (or spells or freshes) play a crucial role in maintaining the ecological health of a river system. Impoundment of water in a reservoir and release or diversion of water for human water needs has significantly altered the magnitude and frequency of flow pulses in many river systems, often reducing river ecological health. A limited...

Challenges abound for water managers attempting to address problems that have cumulative effects. This paper discusses some of these challenges and potential solutions through a case study of farm dam management in the Australian state of Victoria. Farm dams are useful sources of water but also have an impact on the environment because they capture...

Environmental water is being embraced by governments around the world as a means to partly restore rivers impacted by excessive river regulation and to protect those that are not yet overregulated. In cases where environmental water is provided as a water right, managers can make ongoing active management decisions regarding the timing and magnitud...

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...

We present a summary of the works published in Casas-Mulet et al 2016. They consist on the assessment of the ecohydraulics field of research using all available proceedings of the biennial International Symposium on Ecohydraulics for the last two decades. Through the use of Natural Language Processing (NLP), we provide a deep analysis of a longitud...

With the forecast of continued durations of warmer weather, reduced precipitation and stream flow under climate change, freshwater systems have been highlighted as particularly vulnerable ecosystems. Aquatic organisms have been identified to seek thermal refuge in areas of water, which are persistently cooler than the surrounding river and provide...

Tensions between delivering water for human uses versus environmental benefits are increasing in many arid and semiarid regions, potentially causing irreversible environmental consequences. The issue of how to balance these competing uses of water is of fundamental importance, especially with projected increases in the variability of water resource...

Environmental flows aim to mitigate the impacts of modification of riverine flow regimes by restoring components of the natural flow regime. Explicit evidence-based cause–effect relationships between flow regimes and fish responses are required for defensible flow recommendations. However, flow recommendations are typically based on expert opinion...

• 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 respons...

Environmental water managers must make best use of allocations, and adaptive management is one means of improving effectiveness of environmental water delivery. Adaptive management relies on generation of new knowledge from monitoring and evaluation, but it is often difficult to make clear inferences from available monitoring data. Alternative appr...

One important aspect of adaptive management is the clear and transparent documentation of hypotheses, together with the use of predictive models (complete with any assumptions) to test those hypotheses. Documentation of such models can improve the ability to learn from management decisions and supports dialog between stakeholders. A key challenge i...

This paper evaluates an experimental environmental flow manipulation by modeling the counterfactual case that no environmental flow was applied. This is an alternate approach to evaluating the effect of an environmental flow intervention when a before-after or control-impact comparison is not possible. In this case, the flow manipulation is a minim...

Understanding flow-sediment interactions is important for comprehending river functioning. Fine sediment accumulation processes, in particular, have key implications for ecosystem health. However, the amount of fines generated by intragravel flows and later accumulated in gravel streambeds may have been underestimated, as the hydraulic-related driv...

Despite large investments of public funds into environmental flows programs, we have little ability to make quantitative predictions of the ecological benefits of restored flow regimes. Rather, ecological predictions in environmental flow assessments typically have been qualitative and based largely upon expert opinion. Widely applicable, quantitat...

Eco-compensation is the most important form of compensatory conservation in China. However, this compensatory mechanism is criticized for vague definition and massive government participation. For better understanding of eco-compensation in China, this paper compares theories and practices of compensatory mechanisms in China and abroad. The analysi...

Strong national water policy requiring governments to protect environmental water has accelerated efforts to plan and deliver environmental flows across Australia since the mid-1990s. This chapter describes environmental flows assessment methods applied over this period including: hydrological methods widely used at the basin and regional scales, a...

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 rema...

The terrestrial phase of the water cycle can be seriously impacted by water management and human water use behavior (e.g., reservoir operation, and irrigation withdrawals). Here we outline a method for assessing water availability in a changing climate, while explicitly considering anthropogenic water demand scenarios and water supply infrastructur...

Environmental managers often do not have sufficient empirical data to inform decisions, and instead must rely on expert predictions. However, the informal methods often used to gather expert opinions are prone to cognitive and motivational biases. We developed a structured elicitation protocol, where opinions are directly incorporated into Bayesian...

Bioturbation activity by macroinvertebrates in freshwaters may influence the hyporheic exchange processes in river systems. In this study we focussed on understanding how the upward conveyor macroinvertebrates Lumbriculus Variegatus may impact the hyporheic processes through physical alterations of the sediment structure. We aim at investigating; (...

Fine sediment processes in gravel beds may have significant impacts to overall river ecosystem function. In addition to gravitational deposition, horizontal intragravel transport has been recognized to influence fine sediment accumulation. However, the specific hydraulic mechanisms and origin of fine sediment movement are not clearly identified. Th...

Water enters the terrestrial phase of the water cycle when precipitation exceeds evapotranspiration at the land surface. Downstream drainage of this water via surface and subsurface flow paths including transient storage in snowpack, soils, aquifers, and lakes combine to produce the water regimes of freshwater ecosystems. Humans have altered these...

Environmental water management is inherently a multidisciplinary endeavor, but until now there has been no single book that engages experts across all relevant areas of practice and scholarship. This book reflects the growing maturity of environmental water management as a cohesive and specialized field, which finally makes it possible to address t...

Although there has been significant progress in environmental water management across the globe, a number of challenges remain in the establishment and delivery of environmental water regimes on the ground—the implementation challenge. This final chapter focuses on the directions to achieve successful implementation of environmental water policies...

Water quality is a fundamental aspect of aquatic ecosystems, defining the conditions for aquatic flora. changes in water quality may result in immediate changes int he structure and function of ecosystems and have significant effects on other water values and usages. The influences of anthropocentric and natural factors on water quality and quantit...

There is a growing consensus that ecohydrological and hydraulic-habitat tools should be combined when predicting the ecological effects of water management scenarios in rivers. We describe the principles of these technical tools, their predictive power, and their role within more general approaches for defining environmental water regimes. Using re...

Failure to address nonflow stressors and flow-mediated connections through catchments is frequently implicated as the cause of disappointing outcomes from experimental environmental water projects. This is a key reason for considering environmental water management as part of an integrated catchment management (ICM) approach, which aligns efforts a...

Water for the Environment: From Policy and Science to Implementation and Management provides a holistic view of environmental water management, offering clear links across disciplines that allow water managers to face mounting challenges. The book highlights current challenges and potential solutions, helping define the future direction for environ...

There are increasing numbers of rivers with large storages, resulting in changes to environmental condition downstream. In these systems, environmental flow regimes that are specifically designed to meet environmental management objectives, whilst continuing to support economic needs, may be the best approach. A challenge remains as to how best to...

High flow spells (or “pulses”) are important flow components providing ecological triggers and connectivity in rivers. While the ecological importance of flow spells is well-recognized, the link between ecosystem processes and statistical methods used to define flow spells occurrence has received little attention. Commonly, a spell is defined as an...

There is a growing consensus that ecohydrological and hydraulic-habitat tools should be combined when predicting the ecological effects of water management scenarios in rivers. We describe the principles of these technical tools, their predictive power, and their role within more general approaches for defining environmental water regimes. Using re...

A framework for sharing a limited quantity, but also a variable quantity, of water between irrigation and the environment to maximize social wellbeing is developed and illustrated. The optimal water allocation equates the marginal social value of water across different uses. A simplified illustration allocates water from the Goulburn River in north...

The exchange of mass between a stream and its hyporheic zone, or “hyporheic exchange”, is central to many important ecosystem services. In this paper we show that mass transfer across the streambed by linear mechanisms of hyporheic exchange in a gaining or losing stream can be represented by a thin film model in which: (a) the mass transfer coeffic...

The exchange of mass between a stream and its hyporheic zone, or "hyporheic exchange", is central to many important ecosystem services. In this paper we show that mass transfer across the streambed by linear mechanisms of hyporheic exchange in a gaining or losing stream can be represented by a thin film model in which: (a) the mass transfer coeffic...

We assessed how the emerging field of ecohydraulics research has changed over two decades by examining the proceedings of the biennial International Symposium on Ecohydraulics. By using Natural Language Processing (NLP) in word usage, this paper provides a deep analysis of a longitudinal dataset and enables us to test more detailed questions than p...

The basic premise underlying ecohydraulics is deceptively simple: create a new discipline focused on the effects of water movement in aquatic ecosystems by melding principles of aquatic ecology (including aspects of fluvial geomorphology) and engineering hydraulics. However, advancing ecohydraulics as a synthetic, organized field of study is challe...

The advent and development of remote sensing, with now near global coverage at medium scales of spatial resolution, has revolutionised the capacity to map and analyse spatial and temporal variability of the individual components of river ecosystems and aquatic processes in natural and managed systems. In this chapter, remote sensing is deemed to be...

The decline of freshwater fish biodiversity is proceeding at an alarming and persistent rate. Given that most fish must undertake some form of migration in order to complete their life-cycle, of particular concern is the proliferation of hydropower schemes that block migration routes, as well as a variety of other barriers such as weirs and culvert...

The biophysical processes influencing rates of hyporheic exchange are nuanced and not well understood. On the one hand, bedforms are known to promote advective pumping, increasing exchange rates in systems with bedforms compared to those without. By contrast, fine sediment infiltration into stream beds decreases permeability and porosity by cloggin...

Vertical and horizontal fine sediment accumulation during fluctuating flows: outcomes from flume experiments

Streambed hydraulic conductivity is an important control on flow within the hyporheic zone, affecting hydrological, ecological, and biogeochemical processes essential to river ecosystem function. Despite many published field measurements, few empirical studies examine the drivers of spatial and temporal variations in streambed hydraulic conductivit...

The basic premise underlying ecohydraulics is deceptively simple – to meld together principles of ecology and hydraulic engineering to create a new discipline. However, advancing ecohydraulics as a synthetic, organized field of study is challenging because hydraulic engineers and ecologists: 1) study processes that differ substantially in spatial a...

A growing awareness of the impact of changed flow regimes on the environment has led to increasing recognition and legal allocation of environmental water. Where the allocation mechanism allows for active and adaptive management of this environmental water (such as the environmental water entitlements in Australia), environmental water managers mus...

Adequately modelling the ecological outcomes in response to different environmental watering strategies is crucial. This is because water managers use this information to help make decisions on where and when environmental water is delivered. Predicting ecological response to flow in itself is challenging and a complex task since there is incomplet...

Environmental water managers must make best use of scarce water allocations, and adaptive management is one means of improving the effectiveness of environmental water delivery. We developed statistical models designed to inform adaptive management of the threatened Australian grayling (Prototroctes maraena) in the Thomson River, Victoria Australia...

This is the final report, delivered to the Victorian Department of Environment, Land, Water and Planning on Australian Research Council Linkage Project LP100200170. The project primarily analyzed data from the Victorian Environmental Flows Monitoring and Assessment Project (VEFMAP), but also carried out systematic literature assessment and formal e...

Bedforms are a focal point of carbon and nitrogen cycling in streams and coastal marine ecosystems. In this paper we develop and test a mechanistic model-the "pumping and streamline segregation" or PASS model-for nitrate removal in bedforms. The PASS model dramatically reduces computational overhead associated with modeling nitrogen transformations...