Aksar Weir and Nazar Hydropower Project

The new formulation composes of a single weir which has daily reservoir and pressurized tunnel together with surge chamber.

Project Information

Client: Akşar - Nazar Energy

Location: Bitlis

Status: Completed


Key Features

Diversion Type

Installed Capacity 33 MW


High Diversion Weir

Power Tunnel

Surge Tank

Transient Analysis 



Aksar Weir and Nazar Hydropower Project are located in Eastern Anatolia Region within the border of Hizan district of Bitlis province over the creek of Sutopu. Aksar Weir has a catchment areaof 1,000.10 km2 along this river and diverts water to Nazar HEPP.

According to the feasibility report that was prepared in 2005, Akşar Weir and Nazar HEPP was composed of two diversion weirs, a conveyance channel having a length of 10.5 km, forebay, penstock and power house.It was determined that construction of the conveyance channel above the ground is inappropriate in terms of economical and environmental aspects considering field observations and office studies that were conducted by Prosem Engineering. Revised feasibility report was prepared by modifying the formulation which minimizes the cost of expropriation as well as negative social and environmental impacts. The new formulation composes of a single weir which has daily reservoir and pressurized tunnel together with surge chamber. The tunnel which has an inner radius of 4.00 m with modified horse-shoe cross-section and a length of 7,500 m is designed as coated due to geological and hydraulic reasons. The thickness of concrete cover and the amount of reinforcement have been determined considering the hydrostatic pressures over the tunnel. Steel coating has been used at the regions where the hydrostatic pressure was not carried by rock mass over the tunnel and at the regions between the surge chamber shaft and the powerhouse. In order to keep the pressure rises at reasonable levels, surge chamber, having an upper tank with a radius of 15 m and a height of 21 m, was designed at the closest location to the power house considering the suitability of the location in terms of geological and topographical aspects. As a result of all the modifications, a storage of 150 000 m³ has been obtained and the energy production has been shifted to peak hours. Two Francis turbines of equal capacity have been erected in powerhouse. Another turbine having 300 kW capacity has been constructed within the weir in order to take the advantage of the energy of the first water flowing into the creek.