Application of The Wetted Perimeter Method for Predicting Minimum Environmental flow of Beshar River

Minimum environmental flow in rivers provides a certain level of protection for the aquatic environment. In Iran using hydraulic method of wetted perimeter could be a step forward in this field. How to identify the critical point in P-Q curve is still faced with uncertainty in this method. Slope, Curvature and Ideal Point Methods presented by different researchers in this filed. In this article beside description of wetted perimeter method, the environmental flow of Beshar River calculated by using hydraulic parameters. The average of results of Slope, Curvature and Ideal Point Methods is 23%, 8.4% and 20.6% of average annual flow of river, respectively. The results of Slope and Ideal Point Methods are in the acceptable rang of the Tennant method. But the Ideal Point method is superior choice due to the direct use of the chart and more rapidly in calculation.