Mohammad Heydari - PhD graduate at Civil Engineering Dept., Faculty of Engineering, University of Malaya, Kuala Lumpur, Malaysia
Mohammad Sadegh Sadeghian - Assistant Professor, Civil Engineering Dept., Faculty of Engineering, Tehran Central Branch, Islamic Azad University, Iran
Arash Shirzad - MSc Graduated Student at Civil Engineering Dept., Faculty of Engineering, Tehran South Branch, Islamic Azad University, Iran
Hamed Benesi Ghadim - Sustainable and Innovative Bridge Engineering Research Centre (SIBERC), College of Civil Engineering, Fuzhou University, Fuzhou, China

When we encounter the flood remarkably after implementation and during operation, one of the ways to deal with this problem is to increase spillway capacity besides of increasing height of dam. The economic issues related to the plan are another important point, which must also be considered simultaneously. In this paper height, increase of 2.35 meters in Zarrinehrud Dam has been studied through the two mentioned methods: the first way is to increase the spillway crest level to 2.35m by using concrete. The second way is without any changes in the current level of the threshold of labyrinth spillway, the valves are installed with the height of 2.35 meters. In this way, the normal water level will be increased to 1418.35 meters in the reservoir. The purpose of this study is to reach an optimal economic model that leads to find optimal dimensions of the spillway by considering hydraulic efficiency, in such a way that alongside minimizing the total cost, the best hydraulic design is obtained. The optimal model has been solved by using software LINGO applying the optimal model in designing labyrinth spillway in Zarrinehrud dam shows this fact that the choice of twelve labyrinths with a height of 230 m is the economical option. The results of solving the model, by using the restriction for the head, indicate that we are able to travel the designed flood to the reservoir with head 3.60 m by increasing the total length to 574.7 m. This requires 40% cost increase.

Labyrinth Spillway, LINGO, Mathematical Optimization, Magalhaes, Labyrinth weirs