An ecological trajectories architecture for use in the Murray-Darling Basin

Abstract

Tracking the progress of water management actions against Basin Plan objectives in the Murray-Darling Basin requires an ability to forecast the condition of the Basin’s environmental assets into plausible hydrological futures. Understanding and modelling how asset condition changes through time is referend to as trajectory modelling. Asset trajectories originating from a particular starting condition are bound by a range of possible future conditions. This range increases through time in association with different sequences of environmental conditions (created through the flow regime), and is bound by the rate of response of the environmental asset. This rate of response is associated with factors largely intrinsic to the different environmental assets, for example, the rate at which generation of biomass is associated with vegetation recovery. Tracking ecological outcomes through time requires understanding and quantifying environmental water needs, responses to event sequencing and antecedent condition within a broader systems framework. Many factors are likely to influence the extent to which environmental watering can achieve Basin Plan objectives. These include natural variability in the flow regime, strategic (long-term) water management decisions, short-term prioritisation of environmental water and other threats and influences outside of water management (such as multi-species interactions). Throughout the record of historical flows, natural variability has been a major cause of change in environmental condition. Short-term incremental decision-making (or prioritization based upon annual objectives and opportunities) and the uncertainty of future conditions influence the ability to achieve longer-term objectives. The Murray-Darling Basin Authority (MDBA) currently uses a range of ecological modelling tools and methods to inform water management priorities and decision-making within the Basin. In this paper, we outline the development of a method that builds upon existing frameworks and methods used by MDBA and integrates them into a trajectories modelling architecture. The trajectories architecture uses an automated workflow to incorporate the variability of historic flow regimes combined with scenario analyses that are linked to eco-hydrological models. The goal is to develop methods to inform possible outcomes of water management over periods amenable to both long- and short-term decision making processes and align with timelines for Basin Plan objectives and beyond. We demonstrate the architecture using a case-study of woody floodplain vegetation. Show more