A more holistic approach to managing water-dependent ecosystems
Ecosystem functions are a broad suite of processes essential for maintaining health, structure, and integrity of an ecosystem. Consideration of ecosystem functions and how they relate to water dependent ecosystems and hydrology are critical for holistic water management. In the Murray-Darling Basin, the importance of ecosystem functions is recognised in the Water Act, Basin Plan, the Basin-wide Environmental Watering Strategy, and annual watering priorities. However, traditionally there has been a focus on selected species and key sites rather than a more holistic approach to managing water-dependent ecosystems.
A collaborative project between CSIRO and the Murray Darling Basin Authority, the Ecosystem Functions project addressed key ecosystem functions knowledge gaps at basin-scale to inform improved management and delivery of water for the environment in the Murray-Darling Basin. Through four main themes of research, it delivered new knowledge in understanding of ecosystem functions in the Basin.
A central focus of the project was to engage with our stakeholders and the scientific community. This was achieved through a series of workshops, the publication of high-profile research papers, and participation in scientific conferences.
Protecting the environment and the inhabitants of the Murray-Darling Basin
Our research was conducted across four broad ecosystem function themes:
- Hydrological connectivity-several new datasets, including floodplain inundation extent and depth and in-channel water depth and velocity at basin scale, were generated spanning over three decades. These new data layers support analyses and applications that were not possible before, such as determining the volume of water present in the Basin and assessment of historical inundation of different vegetation communities.
- Biological habitat provision-a statistical modelling approach was applied to generate predictions of species occurrence and habitat quality across a time-series of several decades (1995-2020) for the entire Basin. The models developed also identify the important environmental variables for predicting species occurrence and habitat quality over space and time.
- Productivity- the research demonstrated that flow and the connectivity between floodplains and rivers is an important determinant of riverine Dissolved Organic Carbon (DOC) supply. Furthermore, flow and temperature (and season) are important for Riverine Gross Primary Productivity (the amount of carbon fixed during photosynthesis by all producers in the ecosystem) and Ecosystem Respiration.
- Biological connectivity for waterbirds and native fish- this theme focused on quantifying the drivers and likelihood of long-distance, basin-scale movements of waterbirds using straw-necked ibis as a case study species. Statistical modelling indicated that for straw-necked ibis wind strength and direction are primary factors determining the distance travelled during long-distance movements, more so than season. Understanding the role and importance of wind conditions for long-distance waterbird movements is useful knowledge for managers that can be used to enhance movement opportunities through the strategic use of environmental water. In addition, river regulation in the Basin has altered the hydrology and hydraulics of rivers, and created barriers that impede fish movement along rivers (longitudinal connectivity) and onto the floodplain (lateral connectivity). A modelling approach to integrate native fish movement characteristics with improved knowledge of instream barriers and hydraulics was applied at the basin scale. Understanding the impact of barriers on fish movement is crucial for management of fish passage, environmental flows, and for supporting management decisions and the need for intervention.
Addressing knowledge gaps and gaining a deeper understanding of the importance of ecosystem functions
The targeted outcomes of this work were:
- Improved capacity to understand functions of water-dependent ecosystems
- Improved science and tools to inform decision-making, river planning and management of ecosystem functions across the Basin
- Improved ability to communicate to the Australian public, the importance of ecosystem functions and their management.
The project addressed several knowledge gaps that have improved our understanding of ecosystem functions within the entire Basin. It delivered new products not available prior, such as floodplain inundation extent and depth estimation at bi-monthly time steps, long-term habitat mapping for vegetation, waterbirds and fish, and waterbird movement modelling and prediction. The research has built causal relationships between ecosystem functions and flow/connectivity which is imperative to inform improved environmental water management focussing on ecosystem functions. Furthermore, modelling outputs generated from the hydrological connectivity theme are being used and extended by Australian Government funded projects including the Flow Monitoring, Evaluation and Research (FLOW-MER) program and the Murray-Darling Water and Environment Research Program (MD-WERP).
The research has been published in prestigious journals. Links to the papers are provided below.
- The floodplain inundation history of the Murray-Darling Basin through two-monthly maximum water depth maps.
- A Comprehensive Assessment of Floodwater Depth Estimation Models in Semiarid Regions.
- Development of a Multi-Index Method Based on Landsat Reflectance Data to Map Open Water in a Complex Environment.
- A synthesis of floodplain aquatic ecosystem metabolism and carbon flux using causal criteria analysis.