Manno Pond (Mannoike)

Manno Pond, in Manno Town, Kagawa Prefecture, is the largest irrigation reservoir in Japan. It has a circumference of about 20 km and a storage capacity of about 15.4 million cubic meters, and is also called "Manno Taro" by local people. It was designated a national Place of Scenic Beauty in 2019 and is widely known as a pond associated with Kukai, the monk Kobo Daishi. The pond irrigates about 3,000 hectares of farmland and still supports agriculture in Kagawa today.

Construction is dated to the Taiho era (701-704), and tradition says it began in the early eighth century when the Kanakura River was dammed. The pond repeatedly burst and was rebuilt. It is best known for the major repair that Kukai (Kobo Daishi) is said to have directed in 821. After a breach in 1184, the pond was not rebuilt until 1631, and in the meantime the former basin was used as farmland and villages.

The embankment was raised in three stages between 1905 and 1959 to reach its present scale. The pond's name went from Kono (or Jinno) Pond and Mano Pond to Manno Pond, which became established in the Meiji era. No trace of the original embankment survives after later repairs.

From mid-June to early October, about 4 cubic meters of water per second are released from the pond to the paddies of the Sanuki Plain. The start of this release is called "yurunuki". June 15 is also Kukai's birthday, and ceremonies are held in which the sluice gates are opened to send water to the paddies and prepare for rice planting.

On the shore is a rock called Gomadan-iwa, where Kukai is said to have performed a fire ritual during construction. Legends of Kukai, a dragon and tengu also remain. As a landscape, it is known for cherry blossoms in spring and autumn leaves in fall. It was chosen as one of the Soundscapes of Japan in 1996, one of the Top 100 Dam Lakes in 2005 and one of the Top 100 Reservoirs in 2010, and in 2016 was registered as a Heritage Irrigation Structure by the International Commission on Irrigation and Drainage (ICID).

It is about 15 minutes by taxi from JR Kotohira Station or Kotoden Kotohira Station, and about 4 km from the Zentsuji Interchange on the Takamatsu Expressway. Around the pond are Jinno-ji Temple, which stands on its shore and is said to have been founded by Kukai, as well as Jinno Shrine, the Sanuki Mannou National Government Park, Manno Pond Forest Park and Hotarumi Park. The Manno Pond sluice gate is also a nationally registered tangible cultural property.