Charvak Hydroelectric Power Station

The Charvak hydroelectric power station of 600 MW capacity (four 150 MW generating units), one of the largest hydropower plants in Central Asia, is located on the Chirchik river 70 km from the town of Tashkent, the capital of Uzbek SSR. The Charvak hydroelectric development plays an important part in integral development of the National Economy and primarily in irrigation of the fertile land.

The Charvak dam site is located in the upstream reach of the Chirchik River - a right tributary of the Syrdarya River, in a steep-sided and flat bottom canyon, composed of strong lime stone.

The long-term average flow at the dam site totals 208 mVs, the maximum flow on record is 1600 m/s, the long-term average run-off totals 6.6 km³, the long-term average solid run-off is 2.9-1061.

CHARACTERISTIC OF HYDRODEVELOPMENT

The hydropower development consists of a rock and earth fill dam, outlet works located on the left bank and a hydroelectric power station with conveying structures on the right bank.
Length of impoundment structures, m............................770
Maximum head, m...............................................................148
Maximum spillway flow (0.01 % probability), m³/s......2400
Including flow through the powerhouse...........................500
Reservoir storage, 106 m³
Full storage................................2006
Usable storage.........................1580

The Charvak reservoir provides seasonal flow regulation in accordance with irrigation demands accumulating the spring and flood water for irrigation in low water periods (August - September), to augment the flow in the Chirchik-Boz-Sou water course in wintertime and, respectively increase the operational capacity of the hydropower plants located down the river. The surface area of the reservoir at MHWL is 40.1 km².

DAM

The main impoundment structure is a rock and earth fill dam with" a central water-tight core built of loam, sand and gravel filters and shells filled of random rock. The maximum structural height is 168 m. The average upstream and downstream slope is 1 on 2, the fill volume is 18.8-106 m³.

The core foundation houses a grout gallery 3.8X4.0 m in size which was used for consolidation grouting to a depth of 10-12 m and Double-row grout curtain to a depth of 40 to 100 m. The gallery serves also as a cut-off to interface the core with the foundation rock.

OUTLET WORKS

The outlet works consist of a second-tier outlet and a shaft-type emergency outlet.

The second-tier outlet with a discharge capacity of 450 m/s consists of ahead structure, repair gate shaft, 9-m tunnel, repair gate chamber, and outfall conduit.

The shaft-type emergency outlet designed to pass the flow of 1200 m/s, is connected to the end portion of the first-tier diversion tunnel of 11 m in diameter (on the upstream side, the tunnel is sealed with a reinforced concrete plug). The length of spillway front is 56 m. Behind the head structure sill, there is an in let funnel passing into a vertical shaft of 11 m in diameter and 134 m in height. The tailrace tunnel is interfaced with the shaft through a round-section elbow of 10 m in diameter.

HYDROELECTRIC POWER STATION WITH WATER CONVEYING STRUCTURES

Located on the right bank are the power intake, two pressure tunnels and the powerhouse.

The power intake is equipped with trash racks, repair gates and with emergency-repair gates located in the downstream reach. The power tunnels of 9 m in diameter and 770 and 852 m in length are arranged at two levels. The powertunnels terminate in steel bifurcations, one branch per two units. Each generating unit is equipped with a 5 m butterfly valve installed between the bifurcation branch and the scroll case.

The powerhouse of the indoor reservoir type is located at the downstream toe of the dam and measures in plan 102X26.4 m, its maximum height is 44.8 m. The substructure made as an integral concrete block, houses four turbines, scroll cases, draft tubes, turbine rooms and pumping stations.