ABSTRACT
For much of the last century, in standard water allocation practices ecological water needs were often disregarded and ecosystems were left to make do with residual amounts of water left over after all offstream uses received allocations. Water left instream was often considered a waste of a resource. Such practices resulted in severe degradation of freshwater ecosystems, including the loss of over half of the world’s wetlands (Finlayson and Davidson 1999) and nearly 30 percent of freshwater species (WWF 2006). An index of freshwater ecosystem health based on populations of freshwater species showed a decline of 35 percent between 1970 and 2007 (WWF 2010). However, with a growing understanding of the importance of water flow as a “master variable” in determining aquatic ecosystem functioning (Poff et al. 1997), scientists, economists, and policy-makers are increasingly focusing attention on securing sufficient flows for ecological objectives (Petts 1996; Baron et al. 2002; Postel and Richter 2003; Hirji and Davis 2009; Poff et al. 2010).
