Sameura Dam is a multi-purpose dam stretching across Motoyama Town, Nagaoka-gun and Tosa Town, Tosa-gun. It was built in the upper reaches of the Yoshino River. It is managed by the Japan Water Agency and is used for water management, irrigation, industry and electricity generation.
It is 106 meters high with an active storage capacity of 289 million cubic meters and a service water capacity of 173 million cubic meters. Taking the title of biggest dam in Shikoku, its size is equivalent to the total capacity of all the storage reservoirs in Kagawa (15,000 of them!). It was built to tame the Yoshino River and optimize water supplies in all Shikoku. The dam’s operations have considerable consequences for economic and civil life in Shikoku. It is therefore called “The Life of Shikoku” and functions as the heart of this island.
Water in the dam is allocated to 4 prefectures in Shikoku through the Ikeda Dam which stands downstream. 48% of the allocated water goes to Tokushima, 29% goes to Kagawa and 19% to Ehime. Kochi gets the least at just 4%.
The water moves down through the Shikoku Mountains via two diversion weirs from the Seto River to the Jizo-ji River. The flow is diverted to the Kagami Dam, which is a prefectural-run dam in Kochi built on the Kagami River that supplies water to Kochi.
People in Kochi may wonder if their daily water usage will be affected by drought because the Sameura Dam is located in Motoyama Town, but as Kochi only receives 4% of the dam’s allocated water, we can assume that the effect will be minimal.
Drought frequency has recently emerged as a big issue. Serious drought occurs due to the abnormal climate caused by global warming. Droughts in 1994 and 2005 substantially reduced storage capacity in the dam. The water storage rate dropped to 0% in the drought of 2005. A former Okawa Village Office that had previously been submerged by the dam’s waters actually reappeared and became a symbol of the drought. News of prolonged water shortages splashed across headlines, and the drought became a topic of conversation nationwide.
Taken from vol.31 PDF