KOUHRANG HYDRO POWER PLANT HEAD POND, FIRST HYDRAULIC GEOMEMBRANE PROJECT IN IRAN: COMPARISON WITH OTHER VARIANTS

Kouhrang hydropower plant has been designed for generation of electrical energy from Kouhrang River that has been diverged by Kouhrang I and II tunnels from main river to transfer water from Karun basin to Zayande-Rud basin. The hydropower consists of three unit of 13.5 Mw installed capacity. An artificial pond with capacity of 86,000m3 has been designed and constructed to control and regulate discharge and provide 80m design head for turbines. Three penstocks transfer water from head pond to turbines. Three variants were studied for the head pond: zoned embankment with inner clay core, homogeneous embankment with selected shell material, and homogeneous embankment with PVC geomembrane watertight system. The final design of the head-pond is a closed oval shape embankment with random fill and an exposed PVC-Geotextile liner as watertight element. Because of specific condition of project it is shown here how a geosynthetic watertight element is the best solution for project target and how it can save up to 50 % in costs of pond construction as well. This project is the first hydraulic project in Iran with geomembrane liner as watertight element system and could be a representative for studying performance of these systems in Iran. Some information regarding the design and construction details of the geomembrane variant are presented in this paper.