Wide-spread recognition of escalating hydrological alterations of rivers has increased as a result of existing and projected future increases in water demands. The importance of a river’s flow regime for sustaining biodiversity and ecological integrity has been well studied over the last past 4 decades. This paper synthesizes the flow assessment methodologies to understand ecological responses to flow alteration and begins with a compilation of all historical methods to assess environmental flows, evaluates the relationships between ecological responses and flow alteration, describes the research on the new analytic method for developing regional environmental flow standards called the Ecological Limits of Hydrologic Alteration (ELOHA), then
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An increase in water resource developments such as impoundments, diversion weirs, interbasin water transfers, and extraction of water from aquifers have drastically changed flow regimes. The primary water demands include use for agriculture, hydropower generation, industry, and domestic supply, which have impacted ecological ecosystems (Rosenberg et al., 2000). The importance of a river’s flow regime for sustaining biodiversity and ecological integrity has been well studied over the last past 4 decades. These studies have characterized flow regimes on a regional and global scale to understand the hydrologic magnitude, frequency, and timing of flow to develop general guiding principles for management. The development of flow assessment methodologies is used for prescribing environmental flow requirements. Environmental flow regimes in streams and rivers are the primary determinant of the structure and function of aquatic and riparian ecosystems (Poff et al., 1997; Hart and Finelli, 1999; Bunn and Arthington, 2002). Environmental flows are defined as the ‘quantity, timing and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihood and well-being that depend on these ecosystems’ (Sanderson et al., 2012). Flow alteration impacts biodiversity and ecosystem functions of rivers …show more content…
Research has shown that ecological and evolutionary processes in rivers are influenced by changes of historical flow regimes (Poff et al., 1997; Bunn and Arthington, 2002; Lytle and Poff, 2004). This recognition of the importance of quantifying hydrological alteration of rivers on a regional and global scale and its effects on ecology has led to the establishment of varying quantitative and qualitative assessment methodologies. The number of historical environmental flow assessment methodologies exceed over 207 methodologies, recorded for 44 countries (Loar et al., 1986; Gordon et al., 1992; Swales and Harris, 1995; Tharme, 1996; Jowett, 1997; Dunbar et al., 1998). These Environmental flow assessments include everything from basic reconnaissance-level studies that rely on quantitative hydrological methodologies to more comprehensive and complex models, even those lacking baseline data (Arthington et al., 2006; see Poff et al., 2010). Examples of historical hydrologic methods include a modified Tennant method or use of low flow indices that have been used to define the ecological relevance and modified for transferability of techniques across different regions and river types (Tharme, 2003). More structured assessments include complex hydrodynamic habitat
An increase in water resource developments such as impoundments, diversion weirs, interbasin water transfers, and extraction of water from aquifers have drastically changed flow regimes. The primary water demands include use for agriculture, hydropower generation, industry, and domestic supply, which have impacted ecological ecosystems (Rosenberg et al., 2000). The importance of a river’s flow regime for sustaining biodiversity and ecological integrity has been well studied over the last past 4 decades. These studies have characterized flow regimes on a regional and global scale to understand the hydrologic magnitude, frequency, and timing of flow to develop general guiding principles for management. The development of flow assessment methodologies is used for prescribing environmental flow requirements. Environmental flow regimes in streams and rivers are the primary determinant of the structure and function of aquatic and riparian ecosystems (Poff et al., 1997; Hart and Finelli, 1999; Bunn and Arthington, 2002). Environmental flows are defined as the ‘quantity, timing and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihood and well-being that depend on these ecosystems’ (Sanderson et al., 2012). Flow alteration impacts biodiversity and ecosystem functions of rivers …show more content…
Research has shown that ecological and evolutionary processes in rivers are influenced by changes of historical flow regimes (Poff et al., 1997; Bunn and Arthington, 2002; Lytle and Poff, 2004). This recognition of the importance of quantifying hydrological alteration of rivers on a regional and global scale and its effects on ecology has led to the establishment of varying quantitative and qualitative assessment methodologies. The number of historical environmental flow assessment methodologies exceed over 207 methodologies, recorded for 44 countries (Loar et al., 1986; Gordon et al., 1992; Swales and Harris, 1995; Tharme, 1996; Jowett, 1997; Dunbar et al., 1998). These Environmental flow assessments include everything from basic reconnaissance-level studies that rely on quantitative hydrological methodologies to more comprehensive and complex models, even those lacking baseline data (Arthington et al., 2006; see Poff et al., 2010). Examples of historical hydrologic methods include a modified Tennant method or use of low flow indices that have been used to define the ecological relevance and modified for transferability of techniques across different regions and river types (Tharme, 2003). More structured assessments include complex hydrodynamic habitat