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Water management has historically focused on directresource benefits (eg for domestic use, growing food, generating power, supporting industry) to people through economic growth or poverty alleviation. Nevertheless, many global initiatives (eg MA 2005) have highlighted the link between biodiversity, ecosystems, and human well-being. Thus, providing water for the environment indirectly supports people by maintaining ecosystems and a flow of benefits, termed “ecosystem ser-vices”, from them (Fischer et al. 2009). Yet the degrada-tion of freshwater ecosystems resulting from direct human use of water is increasing (Vörösmarty et al. 2010). The quantities, quality, and timing of water flows required to sustain freshwater and estuarine ecosystems and the ser-vices they provide to people are termed “environmental flows ” (Brisbane Declaration; www.eflownet.org). Initially, the definition of environmental flows was based on the need for minimum low flows, since this is considered the limiting factor for maintaining a healthy river ecosystem (Acreman and Dunbar 2004). However, it is now widely recognized that all elements of the flow regime – including floods and low or zero flows – play a role in influencing the biodiversity and functions of freshwater ecosystems (Bunn and Arthington 2002), with too much flow at the wrong time of year or season being just as detrimental as too little flow. Early environmental flow methods focused on valued indicator species (“assets”), assuming that if conditions were appropriate for the most sensitive of these organisms, other species and assemblages would be conserved. Yet the complexity of food webs and feedback loops necessitates targeting a range of species – including plants, fish, algae, inverte-brates, reptiles, amphibians, and birds – spanning wide ecological requirements. Most methods now take a holis-tic systems approach to include a multitude of flow vari-ables representing the whole flow regime, to conserve the major elements of the aquatic ecosystem (ie the preserva-tion of biodiversity and ecosystem integrity). A furthe