The “Zvornik” dam is a concrete gravity structure located on the lower part of the Drina River. It was built (and its reservoir was formed) in 1955. Its catchment area is 17,423 km2. The average river discharge is 399 m³/s.
The dam height is 42 m and its length (without powerhouse) is 167 m. In the middle part of the dam is located the spillway with the stilling basin; along both sides were built two powerhouses with two units each. The spillway capacity is 9,000 m³/s. The reservoir length is 25 km; its main purpose is electricity production. This reservoir provides relatively limited regulation possibilities (daily and weekly water regulation), due to sedimentation.
The dam appurtenant structures include the following: four bottom outlets – tunnel for sediment and floods release, tunnel for releasing of timber, fish ladder, etc. The total bottom outlet capacity is 500 m3/s. The HPP is of run-of-river type. The environmentally guaranteed flow is 60 m3/s.
A preliminary design for rehabilitating the main generating units has been finished in 2009, followed by the tender documents issued in 2013. It is expected that the complete rehabilitation will be completed in 2018. The rehabilitation will increase the total power output of the plant by 30 MW. In addition, a new control room with a 110 kV switchyard was built above the draft tube structure of the right powerhouse. This dam is the only one of the Drina River Basin to have a fish ladder.
The main characteristics of the “Zvornik” HPP and its appurtenant structures are as follows (Mm3 = millions of cubic metres; m.a.s.l. = metres above sea level; 1 GWh = 1 million kWh):
|Total volume||47.43 Mm3|
|Live volume||21.32 Mm3|
|Max. OEL||160.4 m.a.s.l.|
|Normal OEL||157.3 m.a.s.l.|
|Min. OEL||155.0 m.a.s.l.|
|Crest elevation||164.0 m.a.s.l.|
|Max. head||22.7 m|
|Rated head||20.3 m|
|Min. head||17.0 m|
|Installed flow||620 m3/s|
|Installed power||96 MW|
|Annual energy||500 GWh|
|No. of units||4|
|Type of turbine||Kaplan|
Source: IWRM Country Report for Serbia, COWI, Stucky and Jaroslav Cerni Water Institute, 2017