Infrastructure Engineering - Research Publications

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    A predictive model for spatio-temporal variability in stream water quality
    Guo, D ; Lintern, A ; Webb, JA ; Ryu, D ; Bende-Michl, U ; Liu, S ; Western, AW ( 2019-07-23)
    Abstract. Degraded water quality in rivers and streams can have large economic, societal and ecological impacts. Stream water quality can be highly variable both over space and time. To develop effective management strategies for riverine water quality, it is critical to be able to predict these spatio-temporal variabilities. However, our current capacity to model stream water quality is limited, particularly at large spatial scales across multiple catchments. This is due to a lack of understanding of the key controls that drive spatio-temporal variabilities of stream water quality. To address this, we developed a Bayesian hierarchical statistical model to analyse the spatio-temporal variability in stream water quality across the state of Victoria, Australia. The model was developed based on monthly water quality monitoring data collected at 102 sites over 21 years. The modelling focused on six key water quality constituents: total suspended solids (TSS), total phosphorus (TP), filterable reactive phosphorus (FRP), total Kjeldahl nitrogen (TKN), nitrate-nitrite (NOx), and electrical conductivity (EC). Among the six constituents, the models explained varying proportions of variation in water quality. EC was the most predictable constituent (88.6 % variability explained) and FRP had the lowest predictive performance (19.9 % variability explained). The models were validated for multiple sets of calibration/validation sites and showed robust performance. Temporal validation revealed a systematic change in the TSS model performance across most catchments since an extended drought period in the study region, highlighting potential shifts in TSS dynamics over the drought. Further improvements in model performance need to focus on: (1) alternative statistical model structures to improve fitting for the low concentration data, especially records below the detection limit; and (2) better representation of non-conservative constituents by accounting for important biogeochemical processes. We also recommend future improvements in water quality monitoring programs which can potentially enhance the model capacity, via: (1) improving the monitoring and assimilation of high-frequency water quality data; and (2) improving the availability of data to capture land use and management changes over time.
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    A multi-model approach to assessing the impacts of catchment characteristics on spatial water quality in the Great Barrier Reef catchments
    Liu, S ; Ryu, D ; Webb, JA ; Lintern, A ; Guo, D ; Waters, D ; Western, AW (ELSEVIER SCI LTD, 2021-05-14)
    Water quality monitoring programs often collect large amounts of data with limited attention given to the assessment of the dominant drivers of spatial and temporal water quality variations at the catchment scale. This study uses a multi-model approach: a) to identify the influential catchment characteristics affecting spatial variability in water quality; and b) to predict spatial variability in water quality more reliably and robustly. Tropical catchments in the Great Barrier Reef (GBR) area, Australia, were used as a case study. We developed statistical models using 58 catchment characteristics to predict the spatial variability in water quality in 32 GBR catchments. An exhaustive search method coupled with multi-model inference approaches were used to identify important catchment characteristics and predict the spatial variation in water quality across catchments. Bootstrapping and cross-validation approaches were used to assess the uncertainty in identified important factors and robustness of multi-model structure, respectively. The results indicate that water quality variables were generally most influenced by the natural characteristics of catchments (e.g., soil type and annual rainfall), while anthropogenic characteristics (i.e., land use) also showed significant influence on dissolved nutrient species (e.g., NOX, NH4 and FRP). The multi-model structures developed in this work were able to predict average event-mean concentration well, with Nash-Sutcliffe coefficient ranging from 0.68 to 0.96. This work provides data-driven evidence for catchment managers, which can help them develop effective water quality management strategies.
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    Principles for scientists working at the river science-policy interface
    Thompson, RM ; Barbour, EJ ; Bradshaw, CJA ; Briggs, S ; Byron, N ; Grace, M ; Hart, BT ; King, AJ ; Likens, GE ; Pollino, CA ; Sheldon, F ; Stewardson, MJ ; Thoms, M ; Watts, RJ ; Webb, JA (WILEY, 2022-02-20)
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    Robust Climate Change Adaptation for Environmental Flows in the Goulburn River, Australia
    John, A ; Horne, A ; Nathan, R ; Fowler, K ; Webb, JA ; Stewardson, M (FRONTIERS MEDIA SA, 2021-12-06)
    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 combination. Stress testing adaptation results showed that increasing environmental entitlements yielded the largest benefits in drier climate futures, whereas relaxing river capacity constraints (allowing more targeted delivery of environmental water) offered more benefits for current and wetter climates. Combining both these options led to greater than additive improvements in allocation reliability and reductions in environmental water shortfalls, and these improvements were achieved across a wider range of climatic conditions than possible with either of the individual options. However, adaptation may present additional risks to some ecological outcomes for wetter climates. Ultimately, there was a degree of plausible climate change beyond which none of the adaptation options considered were effective at improving ecological outcomes. This study demonstrates an important step for environmental flow assessments: evaluating the feasibility of environmental outcomes under climate change, and the intervention options that prove most robust under an uncertain future.
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    Purposeful Stakeholder Engagement for Improved Environmental Flow Outcomes
    Mussehl, ML ; Horne, AC ; Webb, JA ; Poff, NL (FRONTIERS MEDIA SA, 2022-01-25)
    Rivers are dynamic social-ecological systems that support societies and ecosystems in a multitude of ways, giving rise to a variety of user groups and competing interests. Environmental flows (e-flows) programs developed to protect riverine environments are often conceived by water managers and researchers. This is despite continued calls for increased public participation to include local communities and Indigenous peoples in the development process. Failure to do so undermines social legitimacy and program effectiveness. In this paper, we describe how adaptive management of e-flows allows an opportunity to incorporate a diversity of stakeholder views through an iterative process. However, to achieve this, stakeholder engagement must be intentionally integrated into the adaptive management cycle. Stakeholder engagement in e-flows allows for the creation of a shared understanding of a river and opens collaborative and innovative management strategies that address multiple axes of uncertainty. Here, we describe a holistic framework that unifies current participatory engagement attempts and existing technical methods into a complete strategy. The framework identifies the primary steps in an e-flows adaptive management cycle, describes potential roles of various stakeholders, and proposes potential engagement tools. Restructuring e-flows methods to adequately include stakeholders requires a shift from being driven by deliverables, such as reports and flow recommendations, to focusing on people-oriented outcomes, such as continuous learning and fostering relationships. While our work has been placed in the context of e-flows, the intentional integration of stakeholder engagement in adaptive management is pertinent to natural resources management generally.
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    The politicisation of science in the Murray-Darling Basin, Australia: discussion of 'Scientific integrity, public policy and water governance'
    Stewardson, MJ ; Bond, N ; Brookes, J ; Capon, S ; Dyer, F ; Grace, M ; Frazier, P ; Hart, B ; Horne, A ; King, A ; Langton, M ; Nathan, R ; Rutherfurd, I ; Sheldon, F ; Thompson, R ; Vertessy, R ; Walker, G ; Wang, QJ ; Wassens, S ; Watts, R ; Webb, A ; Western, AW (Taylor & Francis, 2021-10-30)
    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 Basin, Australia’, suggests that a large group of scientists, who work on water management in the Murray-Darling Basin (MDB) including the Basin Plan, have been subject to possible ‘administrative capture'. Specifically, it is suggested that they have advocated for policies favoured by government agencies with the objective of gaining personal benefit, such as increased research funding. We examine evidence for this claim and conclude that it is not justified. The efforts of scientists working alongside government water agencies appear to have been misinterpreted as possible administrative capture. Although unsubstantiated, this claim does indicate that the science used in basin water planning is increasingly caught up in the politics of water management. We suggest actions to improve science-policy engagement in basin planning, to promote constructive debate over contested views and avoid the over-politicisation of basin science.
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    Key factors influencing differences in stream water quality across space
    Lintern, A ; Webb, JA ; Ryu, D ; Liu, S ; Bende-Michl, U ; Waters, D ; Leahy, P ; Wilson, P ; Western, AW (WILEY, 2018-01-01)
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    An Objective Method to Prioritize Socio-Environmental Water Management Tradeoffs Using Multi-Criteria Decision Analysis
    Martin, DM ; Powell, SJ ; Webb, JA ; Nichols, SJ ; Poff, NL (WILEY, 2017-05-01)
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    Using the Weibull distribution to improve the description of riverine wood loads
    Stout, JC ; Rutherfurd, I ; Grove, J ; Webb, JA ; Kitchingman, A ; Tonkin, Z (WILEY, 2017-03-30)
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    The role of floods and droughts on riverine ecosystems under a changing climate
    Parasiewicz, P ; King, EL ; Webb, JA ; Piniewski, M ; Comoglio, C ; Wolter, C ; Buijse, AD ; Bjerklie, D ; Vezza, P ; Melcher, A ; Suska, K (Wiley, 2019-12-01)
    Floods and droughts are key driving forces shaping aquatic ecosystems. Climate change may alter key attributes of these events and consequently health and distribution of aquatic species. Improved knowledge of biological responses to different types of floods and droughts in rivers should allow the better prediction of the ecological consequences of climate change‐induced flow alterations. This review highlights that in unmodified ecosystems, the intensity and direction of biological impacts of floods and droughts vary, but the overall consequence is an increase in biological diversity and ecosystem health. To predict the impact of climate change, metrics that allow the quantitative linking of physical disturbance attributes to the directions and intensities of biological impacts are needed. The link between habitat change and the character of biological response is provided by the frequency of occurrence of the river wave characteristic—that is the event's predictability. The severity of impacts of floods is largely related to the river wave amplitude (flood magnitude), while the impact of droughts is related to river wavelength (drought duration).