Establishing Environmental Water Requirements for the Murray–Darling Basin, Australia's Largest Developed River System

Abstract

There is a global need for management of river flows to be informed by science to protect and restore biodiversity and ecological function while maintaining water supply for human needs. However, a lack of data at large scales presents a substantial challenge to developing a scientifically robust approach to flow management that can be applied at a basin and valley scale. In most large systems, only a small number of aquatic ecosystems have been well enough studied to reliably describe their environmental water requirements. The umbrella environmental asset (UEA) approach uses environmental water requirements developed for information-rich areas to represent the water requirements of a broader river reach or valley. We illustrate this approach in the Murray-Darling Basin (MDB) in eastern Australia, which was recently subject to a substantial revision of water management arrangements. The MDB is more than 1 million km 2 with 18 main river valleys and many thousands of aquatic ecosystems. Detailed eco-hydrologic assessments of environmental water requirements that focused on the overbank, bankfull and fresh components of the flow regime were undertaken at a total of 24 UEA sites across the MDB. Flow needs (e.g. flow magnitude, duration, frequency and timing) were established for each UEA to meet the needs of key ecosystem components (e.g. vegetation, birds and fish). Those flow needs were then combined with other analyses to determine sustainable diversion limits across the basin. The UEA approach to identifying environmental water requirements is a robust, science-based and fit-for-purpose approach to determining water requirements for large river basins in the absence of complete ecological knowledge.

Legacies, lags and long‐term trends: Effective flow restoration in a changed and changing world

“…There has been an investment of >$AUD13B, which has involved a lengthy process of scientific investigation, hydrological modelling and the development of institutional and market structures to reallocate water (Hart, ). Key to this has been the development of sets of eco‐hydrological relationships that have allowed the estimation of a “sustainable diversion limit” for the rivers of the MDB (Swirepik et al., ). The process of reform has been contested politically and scientifically (see Capon & Capon, ; Hart, for a review).…”

Simulating the effect of environmental flow duration on seedling emergence from riparian seed banks of the Upper Hunter River, New South Wales

“…The results from this study did point to some small effects on the amount and timing of seedling emergence that occurs under different flow durations for a range of native, desirable riparian species that occur along rivers in south‐eastern Australia. These findings suggest that seed bank stimulation using environmental flows could be a value‐added benefit from flows allocated for other purposes, and consideration of flow duration is worthy of inclusion in environmental flow allocation planning (Arthington, Bunn, Poff, & Naiman, ; Swirepik et al, ). A further area of research would be to examine how environmental flow releases may assist or damage vegetation, not just seeds, that are established or establishing on bench units within degraded systems such as the Hunter River.…”

Basin‐scale environmental water delivery in the Murray–Darling, Australia: A hydrological perspective

“…This plan sets sustainable diversion limits (SDLs) for the basin's subcatchments (Hart, ,b). SDLs were based on assessment of environmental flow requirements of “Umbrella Environmental Assets,” which were mainly large floodplain wetlands at the downstream end of the basin's major tributaries (Swirepik et al., ). It is assumed that meeting the environmental flow demands of these large wetland systems will likely meet the demands of other ecological values in the basin (Swirepik et al., ).…”