ABSTRACT
With increasing concern for eco-needs, the scientific field of “eco-flows” has prospered in recent years with the result that there are more than 200 methods for their computation. These methods can be grouped into four categories: hydrological rules, hydraulic rating methods, habitat simulation methods, and holistic methodologies (Naiman et al., 2002; Dyson et al., 2003; Postel and Richter, 2003; Tharme, 2003). Past studies include those based on the percentages of natural mean or median annual flow, percentages of total divertible annual flow allocated to wet and dry seasons, and eco-flow prescriptions based on a percentage of total annual base flow plus a high-flow component derived as a percentage of mean annual runoff (Smakhtin et al., 2004). However, such guides have no documented empirical basis and the temptation to adopt them may represent a risk to the future integrity and biodiversity of riverine ecosystems (Arthington, 1998). It is now recognized in the literature that the structure and function of a riverine ecosystem and many adaptations of its biota are dictated by the patterns of temporal variation in river flow or the “natural flowregime paradigm reflected by Indicators of Hydrologic Alteration” (Richter et al., 1996; Poff et al., 1997; Stromberg, 1997; Lytle and Poff, 2004).
