Our study uses fish rishness as water quality metric. Biodiversity provides a wide range of indirect benefits to humans. Several studies have demonstrated that streamflow regimes characterized by discharge volume and variability, and nutrient concentrations regulate aquatic assemblages (Bunn and Arthington, 2002; Lytle and Poff, 2004; Power et al., 2008), and are important predictors of freshwater biodiversity (Mims and Olden, 2012; Chinnayakanahalli et al., 2011; Niu et al., 2012). However, there is still a clear need to obtain information about the cause, type, and persistence of stress on biodiversity and the estimation of the respective impacts on human welfare (Nijkamp et al., 2008). The ecosystem may lose its resilience to disturbance regimes (e.g. streamflow, temperature, sediment, and nutrients) to which the biota are already adapted. Loss of resilience can make the ecosystem more vulnerable to changes that previously could be absorbed (Folke et al., 2004). The U.S. Environmental Protection Agency (USEPA) has implemented the use of biological assessments to directly measure the overall biological integrity of an aquatic community and the synergistic effects of stressors on the aquatic biota (USEPA, 2011). Resident biota can function as biomarkers or environmental indicators of water availability, variability, and degradation and thus can be linked to ecosystem sustainability. Moreover, freshwater biodiversity provides recreational and economic opportunities that are important to local economies and human well-being. Nevertheless, the lack of comprehensive methodologies for providing economic valuation for biodiversity and ecosystem services, the results of which can be easily communicated to policy and decision-makers, has hampered efforts to protect, maintain and enhance habitats and species (Jones-Walters and Mulder, 2009).
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