Evaluation of Environmental Flows in Dalfard River Using Hydrological Methods

Abstract

On the one hand, Iran suffers from limited freshwater resources and, on the other hand, faces increasing demand for water for various uses, which has led to dam construction, especially over the past three decades in Iran. Today, increasing awareness of the effects of water resources development plans on rivers and their dependent ecosystems has led to the estimation of environmental water requirement as one of the essential parts of water resource planning studies in dams. The main objective of this study was to estimate environmental flow in Dalfard River by using Tennant, Tessman, Average Base Flow (ABF) and Flow Duration Curve (FDC) Shifting methods and compare the results methods with each other. The results showed that Tennant method consider 30% mean annual flows for spring and summer ,10% mean annual flows for autumn and winter, 0.24 and 0.08 CMS, respectively. Methods Tessman and ABF, estimate, 0.37 and 0.10 CMS, respectively. According to results, the amounts generated from FDC Shifting method are more proper because of considering the ecological management qualification. Therefore, 0.334 CMS (equals to 42.8% of mean annually flow) was obtained as average environmental requirement of Dalfard River in ecological management class C (maintains minimum ecological term in river). Also moderated class C has good match with regime of flow at several months and is acceptable in area in terms of managerial, agricultural uses, drinking and etc. The suggested method in this research is not the ultimate solution for environmental problems of Dalfard River. Lack of comprehensive required ecological information at river’s ecosystem studies, cause to estimating eco-hydrology by less coefficient of confidence.