- "Once every 10 years, the Lanayru region experiences unusually heavy rainfall. The Zora River flooded every time. The tides damaged not only our domain but our people, washing away poor souls and causing great suffering and disarray. The Zora king of that time, after seeking aid from the king of Hyrule, rode out to see what could be done. By joining the architectural genius of the Zora and Hyrule's technological prowess, East Reservoir Lake was swiftly built. Thanks to this fruitful partnership, Hyrule was no longer plagued by these devastating floods. In gratitude, the Zora king promised the king of Hyrule to manage the reservoir level to protect all of Hyrule from floods. Each Zora king since has kept that oath, spanning 10,000 years. That is why the reservoir signifies our bond with Hyrule."
- — History of the Zora, Part Two - A Reservoir of Hope
The East Reservoir Lake is a location from The Legend of Zelda: Breath of the Wild. It is an artificial lake located in the Lanayru Great Spring region near Zora's Domain. This is the place of the Divine Beast Vah Ruta.
Background and history
According to one of the Zora Stone Monuments written by King Dorephan, the East Reservoir Lake was constructed ten thousands years before the events of Breath of the Wild due to the flooding of the Lanayru province that had plagued the land of Hyrule and Zora's Domain every ten years. The King Zora at that time sought the aid of the King of Hyrule to deal with the problem. By combining Zora architecture and Hyrulean technology, the reservoir was built in a short amount of time. Out gratitude, the King Zora swore to manage the water level of the reservoir to protect all of Hyrule from flooding, an oath that had been kept by each subsequent king for ten thousands years. As a result, the reservoir has become a symbol of the Zora's bond with the Kingdom of Hyrule and Hylian people.
The return of the Divine Beast Vah Ruta a century after the Great Calamity produced the never-ending torrential rains, threatened to cause the water level to rise to the point of flooding. This forced Prince Sidon to attempt to confront Vah Ruta to put a stop to the rain. However the source of the water could only be deactivated by the use of Shock Arrows which Zora are generally incapable of touching for long periods due to their natural vulnerability to electricity. This forces Prince Sidon to seek the aid of races capable of touching them. He eventually settled on finding a Hylian against the wishes of most of the Zora Elders who blamed the Hylians, especially Link, for the Great Calamity that lead to the death of Sidon's elder sister and Zora Champion Mipha. Prince Sidon encounters Link who had come to free Vah Ruta from Calamity Ganon's control. They manage together to stop the rain as Link defeats Waterblight Ganon freeing both Vah Ruta and the trapped spirit of Mipha. This event restores the bond between the Hylian people and Zora that the reservoir signifies.