Determining the environmental flow requirement using hydraulic method in data scarce in Cheshmeh Langan River

Today, the use of surface water to meet various human requirements such as drinking, agriculture and industry has endangered the health of this river ecosystem and its role in the natural system. The minimum environmental flow in the river provides a safe level of protection for the water-dependent environment. In the present study, the environmental flow requirement of three stations of Cheshmeh Langan River located in Isfahan province were calculated by two hydraulic methods slope and maximum curvature of wetted perimeter. The results showed that both slope and curvature methods estimate the same minimum environmental flow requirement. So that the difference between the two methods in S1 station was about 0.07m3/s. According to the discharge measured at station S1, minimum environmental flow requirement is provided in all months except December. While the measured discharge at S2 and S4 stations cannot provide the minimum environmental flow requirement due to the impact of the dam and water transfer in any of the months. The flow of 0.39 m3/s for the first station (S1) and 1.44 an 1.68 m3/s for the second and third stations, respectively has been proposed as the minimum environmental flow requirement of Cheshmeh Langan River. The results of this study showed that the environmental flow requirement can be estimated using hydraulic method in data scarce.