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Cross-Cutting Theme: Modelling

A challenge for managing Commonwealth environmental is how to apply our knowledge about individual sites or species to large spatial scales and whole ecosystems. Modelling can help us to do this by developing methods to model the response of aquatic ecosystems to Commonwealth environmental watering. Work in this theme will focus on solutions to issues associated with understanding how different species respond to flows, and how to create the building blocks for a Basin-wide, multiple species model of response to environmental watering.

Image: Reed warbler in a wetland in the Murray catchment. Photo credit: Danial Stratford

Why will modelling assist in environmental water outcomes?

Modelling enables us to take detailed knowledge and extend it to be relevant to the spatial and temporal scales at which management decisions need to be made – ultimately the whole of the Murray-Darling Basin.

Most managers and scientists rely on their own perceptions and experience when making decisions about environmental watering –we term this their ‘mental model’. These mental models provide individuals with expectations about how an ecosystem would respond to environmental watering, and what the risks and benefits might be. Different managers may, however, have different models. It can be difficult to identify cause-and-effect pathways as the accuracy of mental models is difficult to assess, also, mental models leave an organisation if individuals move on.

Using models can make knowledge transparent, so that it is transferrable in space and time, and clearly identifies and reduces individual bias. Cause and effect pathways can be tested and used in adaptive management to improve both knowledge and management practice. This means that models provide an objective and repeatable assessment of the likely impact of a given management action, like environmental watering.

Models also provide us with the opportunity to run ‘what-if’ scenarios so that we can improve our understanding of the impact of environmental watering compared with a business-as-usual approach (i.e. to understand the impact of the environmental water itself), or for example, assess the impact of environmental water under a range of climate scenarios.

Image: Flow-MER modelling team at work. Photo credit: Ashley Macqueen

Our approach

The approach of the Modelling cross-cutting Theme will give us tools to expand our understanding of individual species at specific locations, and at specific times, into a holistic assessment of the ecological response of the Basin to environmental watering. It will provide the necessary building blocks to create a Basin-wide model of ecological response that will be a powerful tool in quantifying the overall benefit of Commonwealth environmental water in the Murray-Darling Basin. 

One of the primary ways in which modelling will assist in the evaluation of Commonwealth environmental water outcomes is by quantifying those outcomes. We already have models of hydrology (water movement), weather and other physical processes for the Murray-Darling Basin. These models enable managers to understand the current physical condition of the Murray-Darling Basin and, importantly, to compare that to the condition that would be expected in the absence of environmental water (a so-called ‘counterfactual’).

While models of many of the physical conditions in the Murray-Darling Basin are well developed, however, there is no single model of ecological response at the Basin scale. Moreover, the effect of environmental water on ecological response depends on a range of environmental factors, in addition to the volume of water, and so can differ at different locations and times. This makes it extremely difficult for managers to create a holistic assessment of the change in ecological condition as a result of environmental watering.

This means that the benefits of Commonwealth environmental watering cannot currently be objectively quantified at the scales of many of the management decisions. Our work will create the architecture for a Basin-wide ecological model that will move us closer to being able to understand the ‘ecological counterfactual’ for the Basin.  This will enable managers to quantify the benefits of Commonwealth environmental watering holistically and transparently.

A dry Narran River channel – upstream from Bangate Bridge – 7 December 2019. Photo credit: CEWO
Narran River flowing at ~2,500ML/d upstream from Bangate Bridge – 28 February 2020. Photo credit: CEWO

Current activities

We will be working closely with the other Themes and Selected Areas to collate data and draw on their detailed knowledge. With them, we will be analysing data to capture specific responses to flow for our initial target species in our initial location. We will be collating broad-scale data from satellites and models to provide a foundation for our Basin-wide assessment of condition, and undertaking modelling and analyses to understand species interactions and the links between condition in the Basin and the species that we have selected.

Another important group we will be working with are environmental water managers so that we can understand what measures are most useful for them, and ensure that our outputs are aligned with management needs. We will then explore the value of a range of integrative variables and extrapolation measures. Throughout, we will be sharing our learnings about how species respond, how such responses can affect other species and how to use our detailed local knowledge to understand other times and places.

We are undertaking two closely-linked approaches:

Establishing relationships between ecological response and flow regime

We will work with Flow-MER Themes to provide robust analysis of data to understand and quantify the relationships (and uncertainty) between environmental outcomes and flow for aquatic ecosystems within the Basin. We will then use this understanding to generate response relationships to describe and quantify potential ecological conditions as outcomes of the flow regime.

Understanding these relationships enables us to then apply this knowledge to new locations within the Basin, with or without Commonwealth environmental water. This will enable us to quantify outcomes in unmonitored areas and scale to a basin-wide understanding to support the evaluation of the potential benefits of Commonwealth environmental water at basin-scales.

Stony creek frog (Ranoidea (Litoria) wilcoxii) in the upper catchment of the Condamine river. Photo credit: Danial Stratford

Developing model architecture to integrate the outcomes across themes

This research will involve collating remotely-sensed data (e.g. from satellites) along with existing models (e.g. of water movement and soil moisture) to get a Basin-wide assessment of physical condition. We will use this to develop relationships with species responses to environmental watering. This will be based on times and places where we have the best knowledge, taking into account other factors that mediate the response to flow, such as local weather and land use.

A key challenge here will be to understand how the response of one species may influence the response of another species (e.g. increased fish abundance as a result of environmental watering may provide more food for fish-eating birds). Initially, we will focus on a few species for a single well-studied site, but we will then look to expand our assessment to other similar sites and to incorporate more species.

Nankeen night heron in a wetland in South Australia. Photo credit: Danial Stratford

Image: Refuge pool in the Darling River during low flows. Photo credit: Danial Stratford

Our team

Dr Danial Stratford

Danial is an aquatic ecologist and ecological modeller with CSIRO Land and Water in the Modelling Water Ecosystems team with a background in modelling the environmental outcomes resulting from changes in flow regimes. He has a broad range of experience from within the Murray-Darling Basin, northern Australia and internationally, and has delivered to a range of stakeholders and clients. Danial uses a range of approaches and draws upon skills in statistical analysis, statistical modelling and mechanistic modelling to understand, quantify and predict the environmental outcomes of flow events, flow sequences and flow regimes. He specialises in understanding temporal dynamics and scenario analysis, linking hydrological data to quantify environmental outcomes under uncertainty. The core of Danial’s work is to deliver products and knowledge to improve the environmental outcomes associated with water management at a range of spatial and temporal scales.

Associate Professor Rebecca Lester

Rebecca is an ecologist with experience in freshwater, estuarine and marine systems.  She has wide-ranging research interests, but is primarily focused on the management of aquatic ecosystems and in achieving good ecological outcomes in systems that involve multiple uses and commercial industries.  She combines her expertise in ecology with a solid background in hydrology and erosional processes and actively collaborates across biological and other disciplines. She has a broad range of analytical and modelling skills and specialises in combining data about a range of physical and biological processes into a broader understanding at an ecosystem scale, giving her the requisite skills to participate in this project. For more information, visit qael.org.

Dr Galen Holt

Galen is an ecologist and postdoctoral research fellow at Deakin University. He is interested in the large-scale responses of species and communities to environmental conditions at large spatial and temporal scales. Of particular interest is how rigorous, process-based understanding of large-scale ecological outcomes can inform management decisions. His background is primarily in aquatic community ecology, where he studies how species and communities respond to varying environmental conditions in space and time. His research encompasses empirical studies of aquatic insects, statistical analyses, theory, and development of large simulation models. He takes a varied modelling approach, ranging from quite generic models to understand fundamental ecological processes, to the development of models incorporating empirical data to capture dynamics of specific communities with targeted management goals. For more detail, visit qael.org.

Dr Luke Lloyd-Jones

Luke is a CSIRO Research Scientist with DATA61. Luke is an applied statistician with experience in applications in ecology, fisheries, and human genetics, including very large and complex datasets. He focuses on the development and implementation of novel statistical and machine learning methods and provides high-level analytical and statistical modelling expertise for the vast amounts of interesting data being generated by the CEWO waterbird movement tracking project and also contributes to reporting and manuscript preparation.

Dr Ashmita Sengupta

Ashmita is a Senior Research Scientist at Land and Water CSIRO and ecohydrologist with expertise in optimization, adaptive management of water resources geared to protect ecosystem health, sustainable low impact development design, and system vulnerabilities under climate change and other pressures.

Ashley Macqueen

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