Methodologies for the Assessment of Environmental Flows Chapter 6

The previous chapter discussed the emergence of concerns for diminishing flows in rivers during the 1950s in the USA and the consequential evolution of the concept of environmental flows. Parallel developments occurred worldwide in the understanding of river ecosystems (see chapter 2) and the impacts of flow regulation on ecosystem components other than fish (chapter 4). Accordingly, the methodologies for the assessment of flow requirements in the rivers were also developed to meet the gradually widening scope of the subject. During the past four decades, hundreds of studies were made across the world to develop, apply and adapt numerous methods of environmental flow assessments (EFAs). These methods have been critiqued, evaluated and reviewed frequently in a variety of publications (Stalnaker and Arnette 1976, Jowett 1997, Dunbar et al. 1998, Annear et al. 2002, Arthington 2012, Hatfield et al. 2013, Linnansaari et al. 2013). Most reports on the studies of environmental flows start with a review which usually covers similar ground. The geographical spread and use of different methods around the world has been reviewed by Tharme (2003). This chapter provides another overview of developments in a historical perspective describing briefly the more important methods, with some comments on their limitations and advantages.