Replacement of PHABISM univariate method by fuzzy approach as requirement for environmental flow assessment in rivers (case study, Jajrood river)

Assessment of environmental flow regime based on regional ecological status is the supreme method which has been approved by broad previous researches. Although ecological weakness points PHABISM univariate method is inevitable, this method has been applied in developed and developing countries.Present research uses fuzzy logic approach as an improved habitat model to simulate river habitats and demonstrate that replacement of PHABISM univariate method by fuzzy approach in national and regional environmental flow regime assessment in rivers is essential. By applying physical habitat simulation in Jajrood river by two described methods which were PHABSIM univariate habitat model and fuzzy based habitat simulation, WUA curves have been obtained. According to results, PHABISM univariate habitat method assesses environmental flow regime more than real needs of river and it could dramatically deteriorate challenges between environmental managers and stakeholders. It is strongly recommend to avoid use of PHABSIM univariate physical habitat models for environmental flow assessment in rivers or streams and ecologists must shift on fuzzy based approaches for further studies.