A comparison of the influence of the Sattarkhan reservoir dam on the upstream and downstream of the Ahar Chai River, NW Iran

Abstract

Rivers are one of the most important sources of water supply in the world. Reduction of water supply and resources reveals the necessity of investigation of water character changes. Construction of the Sattarkhan reservoir dam changed the morphological parameters such as stream velocity and sedimentary process of the Ahar Chai River. Identifying the changes of the river morphology is very important to avoid disasters in the future. In this paper, the morphology of the Ahar Chai River prior to the reservoir construction and changes of the river bed after the reservoir construction are studied and compared quantitatively. Two series of data of pre- and post-reservoir dam construction were collected from the hydrometric stations and field works. The annual sediment and water supply were estimated using daily measurement in hydrometric station and the HEC-RAS model was used to calculate the hydraulic parameters for each year using cross-sections. Cross-section forms depend on water discharge, slope, sediment supply, bed rock, etc. The investigations show that downstream of the reservoir is more eroded than the upstream after the reservoir dam construction and also exhibits a major decrease in the sediment supply. On the other hand, before the reservoir dam construction, there was a similar situation in all cross-sections; however, downstream is more affected and all parameters are totally moderated after the reservoir dam construction.