In the Murray-Darling Basin, consumptive water use coupled with high natural variability in river flows has resulted in declines in environmental condition in many ecological systems. The Murray-Darling Basin Plan provides a mechanism to support improved environmental outcomes with the recovery of water for environmental purposes. Understanding how and when the recovered environmental water is best put to use, as well as understanding the progress made towards achieving Basin Plan objectives can be assisted by not only understanding how environmental condition changes through time, but also, by having a probabilistic view of future flow conditions.
Trajectory modelling aims to address these needs by forecasting a plausible range of probabilistic environmental outcomes into the future. Recent advances in ecological modelling approaches used within the Basin, including the development of methods that link temporal dynamics of environmental change to flow, facilitate the modelling of environmental trajectories. However, current applications of these methods have limited ability to quantify the probability of different flow events into the future, and hence, environmental outcomes out to specific time periods from the present.
The aim of the trajectories project of the MDBA-CSIRO Eco-hydrology partnership is to develop a modelling approach to predict spatial and temporal trajectories of ecological change as a result of water management, climate variability and climate change. To support water management decisions, this project is developing an environmental trajectories framework that considers change in asset condition through time as an outcome of the flow regime. This trajectories framework brings together the current scientific understanding of the water requirements of fish and floodplain vegetation communities to model how their condition is likely to change as a result of both forecast and probabilistic flow sequencing over different time periods into the future and represent forecast environmental condition spatially across the southern Basin.
The MDBA-CSIRO Ecohydrology partnership project is developing a scientific architecture and software tool to guide the MDBA in their water management strategies for representative environmental assets from different Basin Plan themes (fish and vegetation).
It is anticipated that a trajectories framework can open the door to a range of applications including: 1) comparison of relative outcomes from different management scenarios into the future; 2) tracking environmental progress towards Basin Plan objectives; 3) prioritisation of delivery of environmental water in decision settings based upon antecedent and current environmental conditions; 4) understanding where trade-offs occur from different management decisions; and 5) to understand and quantifying the range of influence associated with water management in the Basin compared to other drivers including variability.