Zainsk Reservoir or Zay Reservoir (Russian: Заинское водохранилище, Tatar: Cyrillic Зәй сусаклагычы, Latin Zäy susaqlağıçı) is a reservoir of the Zay River near Zainsk, Tatarstan, Russian Federation. It was filled in 1963 to be a cooling pond for Zainsk TTP. It has surface area 20.5 km², a length 12 km, mean width 1.7 km, mean depth 3.1 m and a volume 63 million cubic meters.
Coordinates: 55°16′44″N 52°02′23″E / 55.27889°N 52.03972°E / 55.27889; 52.03972
Zainsk (Russian: Заи́нск; Tatar: Cyrillic Зәй, Latin Zäy) is a town in the Republic of Tatarstan, Russia, located on the Stepnoy Zay River (Kama's tributary), 287 kilometers (178 mi) east of Kazan. Population: 41,803 (2010 Census); 41,088 (2002 Census); 36,621 (1989 Census).
Zainsk Reservoir, along the Zay River, is located near the town.
It was founded in 1652–1656 as a fortress. It was granted urban-type settlement status in 1962, and was known as Novy Zay (Новый Зай) until 1978, when it was granted town status and renamed Zainsk.
Within the framework of administrative divisions, Zainsk serves as the administrative center of Zainsky District, even though it is not a part of it. As an administrative division, it is, together with the settlement of Karmalka, incorporated separately as the town of republic significance of Zainsk—an administrative unit with the status equal to that of the districts. As a municipal division, the town of republic significance of Zainsk is incorporated within Zainsky Municipal District as Zainsk Urban Settlement.