Vacha Reservoir (Bulgarian: Въча язовир Yazovir Vacha; before 1999: Antonivanovtsi Reservoir) is a body of water associated with a dam in Devin Municipality, south Bulgaria. It is part of the Vacha Cascade Joint Implementation Project involving three more dams and four power stations. The two other existing dams on the Vacha River are the Kamak Dam and the Tsankov Dam; the Krichim Dam is in the implementation stage.
Completed on 5 November 1975, the Vacha Dam is situated 680 metres (2,230 ft) above sea level. The dam was designed by Bulgarian hydroengineers, though their work was overseen by Russian, Japanese and Italian experts. It is a concrete gravity structure of 144.5 metres (474 ft) height, making it the tallest dam in Bulgaria. Its pumped storage power plant has a capacity of 160 MW.
The Vacha Dam Reservoir has been created as a part of cascade development on the Vacha River in southern Bulgaria. Vacha River, one of the main right tributaries of the Maritsa, is the second longest river that has its source in the Rhodopes, the Arda being the longest. It is 105 kilometres (65 mi) long and is formed by the confluence of the rivers Chairdere and Buynovska. The Vacha runs through the Rhodopes forming a deep valley where the two dams, the Krichim and Vacha, are located.
The reservoir lies 40 km (25 mi) from Plovdiv, one of Bulgaria’s major cities, and a potential breach in the dam walls would gravely endanger the city. In the direct vicinity of the reservoir is the town of Krichim.