William J. Young

Large-scale patterns of erosion and sediment transport in river networks, with examples from Australia

This paper examines the patterns of sediment transport in rivers in terms of the sources of sediment and its transport and deposition through the river network. The analysis is in the context of dramatic human influences on river sediment transport and how they might influence freshwater ecosystems. The review of Australian work shows that erosion of hillslopes and stream banks has greatly increased in historical times, supplying vast quantities of sediment to rivers, much of which is still stored within the river system. The stored sediment will continue to effect in-stream and estuarine ecosystems for many decades. In most Australian catchments the dominant source of sediment is streambank erosion. An analysis of historical channel widening suggests that a conceptual framework of relative stream power can explain the diversity of behaviour observed in the numerous case studies. Sediment delivery through catchments is considered first in a generic whole network sense, which emphasizes the crucial role played by riverine deposition in determining catchment sediment budgets. A method is then presented for analysing the diverse spatial patterns of sediment storage in any river network. Finally, the paper considers the temporal changes to channel morphology in response to a human-induced pulse of sediment.

Delivering environmental decision support systems: software tools and techniques

A suite of “desirable features” for Environmental Decision Support Systems (EDSS) is proposed by identifying the general attributes of environmental systems which are of importance to modelling and simulation, and the different categories of users of EDSSs. With these features as a guide, a review and discussion of the approaches to delivering Environmental Decision Support Systems is presented. The two most efficient approaches are: (i) the use of modelling and simulation software tools, and (ii) the use of model integration and re-use techniques. A review of the currently available software tools for environmental modelling and simulation is therefore presented, and an overview of the current research activities in model integration and re-use is provided. Numerous existing EDSS are used as examples of the different approaches throughout the review. The review highlights the advantages and disadvantages of the two main approaches to EDSS delivery, and subsequently discusses the role emerging information technologies may play in the future delivery of EDSS. The paper concludes that while the available software for modelling and simulation is very advanced, some of the desirable features of EDSS (such as representation of spatial data and provision of expert help) cannot be easily delivered using such software. While the research activities in model integration and re-use are making real advances, especially in delivering those features which cannot currently be provided using modelling and simulation software, this is not occurring in any coordinated or synergistic manner. The ultimate goal should be to provide a fully general EDSS development platform which would allow system analysts to develop EDSS for any environmental domain complete with all desirable features. This is still considered to be very much a long-term ambition.

A Ramsar wetland in crisis – the Coorong, Lower Lakes and Murray Mouth, Australia

The state of global freshwater ecosystems is increasingly parlous with water resource development degrading high-conservation wetlands. Rehabilitation is challenging because necessary increases in environmental flows have concomitant social impacts, complicated because many rivers flow between jurisdictions or countries. Australia’s Murray–Darling Basin is a large river basin with such problems encapsulated in the crisis of its Ramsar-listed terminal wetland, the Coorong, Lower Lakes and Murray Mouth. Prolonged drought and upstream diversion of water dropped water levels in the Lakes below sea level (2009–2010), exposing hazardous acid sulfate soils. Salinities increased dramatically (e.g. South Lagoon of Coorong >200 g L–1, cf. modelled natural 80 g L–1), reducing populations of waterbirds, fish, macroinvertebrates and littoral plants. Calcareous masses of estuarine tubeworms (Ficopomatus enigmaticus) killed freshwater turtles (Chelidae) and other fauna. Management primarily focussed on treating symptoms (e.g. acidification), rather than reduced flows, at considerable expense (>AU

Environmental flows for natural, hybrid, and novel riverine ecosystems in a changing world

2 billion). We modelled a scenario that increased annual flows during low-flow periods from current levels up to one-third of what the natural flow would have been, potentially delivering substantial environmental benefits and avoiding future crises. Realisation of this outcome depends on increasing environmental flows and implementing sophisticated river management during dry periods, both highly contentious options.

The changing role of ecohydrological science in guiding environmental flows

The term “environmental flows” describes the quantities, quality, and patterns of water flows required to sustain freshwater and estuarine ecosystems and the ecosystem services they provide. Environmental flows may be achieved in a number of different ways, most of which are based on either (1) limiting alterations from the natural flow baseline to maintain biodiversity and ecological integrity or (2) designing flow regimes to achieve specific ecological and ecosystem service outcomes. We argue that the former practice is more applicable to natural and semi-natural rivers where the primary objective and opportunity is ecological conservation. The latter “designer” approach is better suited to modified and managed rivers where return to natural conditions is no longer feasible and the objective is to maximize natural capital as well as support economic growth, recreation, or cultural history. This permits elements of ecosystem design and adaptation to environmental change. In a future characterized by altered climates and intensive regulation, where hybrid and novel aquatic ecosystems predominate, the designer approach may be the only feasible option. This conclusion stems from a lack of natural ecosystems from which to draw analogs and the need to support broader socioeconomic benefits and valuable configurations of natural and social capital.

Ecosystem science: toward a new paradigm for managing Australia's inland aquatic ecosystems.

Abstract The term “environmental flows” is now widely used to reflect the hydrological regime required to sustain freshwater and estuarine ecosystems, and the human livelihoods and well-being that depend on them. The definition suggests a central role for ecohydrological science to help determine a required flow regime for a target ecosystem condition. Indeed, many countries have established laws and policies to implement environmental flows with the expectation that science can deliver the answers. This article provides an overview of recent developments and applications of environmental flows on six continents to explore the changing role of ecohydrological sciences, recognizing its limitations and the emerging needs of society, water resource managers and policy makers. Science has responded with new methods to link hydrology to ecosystem status, but these have also raised fundamental questions that go beyond ecohydrology, such as who decides on the target condition of the ecosystem? Some environmental flow methods are based on the natural flow paradigm, which assumes the desired regime is the natural “unmodified” condition. However, this may be unrealistic where flow regimes have been altered for many centuries and are likely to change with future climate change. Ecosystems are dynamic, so the adoption of environmental flows needs to have a similar dynamic basis. Furthermore, methodological developments have been made in two directions: first, broad-scale hydrological analysis of flow regimes (assuming ecological relevance of hydrograph components) and, second, analysis of ecological impacts of more than one stressor (e.g. flow, morphology, water quality). All methods retain a degree of uncertainty, which translates into risks, and raises questions regarding trust between scientists and the public. Communication between scientists, social scientists, practitioners, policy makers and the public is thus becoming as important as the quality of the science. Editor Z.W. Kundzewicz Citation Acreman, M.C., Overton, I.C., King, J., Wood, P., Cowx, I.G., Dunbar, M.J., Kendy, E., and Young, W., 2014. The changing role of ecohydrological science in guiding environmental flows. Hydrological Sciences Journal, 59 (3–4), 433–450

Linking water-resource models to ecosystem-response models to guide water-resource planning -- an example from the Murray--Darling Basin, Australia

Freshwater ecosystems are a foundation of our social, cultural, spiritual and economic well being. The degraded condition of many of Australias river ecosystems is testament to our failure to manage these resources wisely. Ecosystem science involves the holistic study of complex biophysical systems to understand the drivers that influence ecological pattern and process. Ecosystem science should underpin both water management and policy. Our understanding of aquatic ecosystems lags behind the increasing problems caused by past land and water management. Current post-graduate training programmes will not provide the aquatic ecosystem scientists needed by government and management agencies to prevent further degradation. We advocate new initiatives to capture the skills, knowledge and innovation of our research community by engaging scientists and managers in large-scale, long-term ecosystem science programmes across Australia and to integrate these programmes with community aspirations, policy, planning and management. We call on management agencies to increase their support for and uptake and use of ecosystem science. We also advocate establishment of national archives for long-term ecologically-relevant data and samples, and clear custodial arrangements to protect, update and facilitate knowledge-transfer. These initiatives need to be supported by more extensive, better-funded post-graduate and post-doctoral programmes in ecosystem science and management.

Development of an environmental flows decision support system

Objectively assessing ecological benefits of competing watering strategies is difficult. We present a framework of coupled models to compare scenarios, using the Coorong, the estuary for the Murray–Darling River system in South Australia, as a case study. The framework links outputs from recent modelling of the effects of climate change on water availability across the Murray–Darling Basin to a hydrodynamic model for the Coorong, and then an ecosystem-response model. The approach has significant advantages, including the following: (1) evaluating management actions is straightforward because of relatively tight coupling between impacts on hydrology and ecology; (2) scenarios of 111 years reveal the impacts of realistic climatic and flow variability on Coorong ecology; and (3) ecological impact is represented in the model by a series of ecosystem states, integrating across many organisms, not just iconic species. We applied the approach to four flow scenarios, comparing conditions without development, current water-use levels, and two predicted future climate scenarios. Simulation produced a range of hydrodynamic conditions and consequent distributions of ecosystem states, allowing managers to compare scenarios. This approach could be used with many climates and/or management actions for optimisation of flow delivery to environmental assets.

Corrigendum to: Large-scale patterns of erosion and sediment transport in river networks, with examples from Australia

Abstract The Murray–Darling Basin in Australia is severely environmentally degraded as a result of a range of anthropogenic changes, most notably the regulation and extraction of surface water resources for irrigated agriculture. Environmental problems include eutrophication of rivers and storages, elevated salinity levels, widespread blooms of toxic blue–green algae, decline of native fish and bird populations, and reduction of area of riverine wetlands. Both the community and the government are committed to improving the state of the environment in the Basin, both for its intrinsic ecological values, and to ensure the sustainability of production in what is Australias most economically important agricultural region. To facilitate the on-going trade-off process between competing users of this resource, a decision support system (DSS) is being developed which will enable explicit prediction of the likely response of key features of the riverine environment to proposed flow management scenarios. The DSS is being developed using the RAISON shell ( Lam, D.C.L., Mayfield, C.I., Swayne, D.A., Hopkins, K., 1994. A prototype information system for watershed management and planning. Journal of Biological Systems 2 (4), 499–517 ), and will integrate a range of simple models of riverine ecology which are being developed. These models will include qualitative and quantitative models representing the response of different aspects of the instream and floodplain ecology dependent upon the river flow regime. The DSS will not include a detailed model of river hydrology or hydraulics, but rather, will use the output from the range of such models currently in use in the Basin as inputs to the ecological models. The DSS will also provide a range of tools to allow user-defined evaluation of scenario results, as well as explanations and supporting information to elucidate the ecological modelling.

Assessment of Ecological Responses to Environmental Flow Regimes using a Decision Support System Framework

This paper examines the patterns of sediment transport in rivers in terms of the sources of sediment and its transport and deposition through the river network. The analysis is in the context of dramatic human influences on river sediment transport and how they might influence freshwater ecosystems. The review of Australian work shows that erosion of hillslopes and stream banks has greatly increased in historical times, supplying vast quantities of sediment to rivers, much of which is still stored within the river system. The stored sediment will continue to effect in-stream and estuarine ecosystems for many decades. In most Australian catchments the dominant source of sediment is streambank erosion. An analysis of historical channel widening suggests that a conceptual framework of relative stream power can explain the diversity of behaviour observed in the numerous case studies. Sediment delivery through catchments is considered first in a generic whole network sense, which emphasizes the crucial role played by riverine deposition in determining catchment sediment budgets. A method is then presented for analysing the diverse spatial patterns of sediment storage in any river network. Finally, the paper considers the temporal changes to channel morphology in response to a human-induced pulse of sediment.