Lake Tokiwa is the largest lake in Yamaguchi Prefecture located in the southeast portion of Ube City (9.4ｍ embankment height, 65ｍ embankment length, 3800 ㎥ embankment area, 3,767,700t reservoir capacity, 809,000 ㎡ reservoir surface area, 3,450,000 ㎡ catchment area). It~s a popular tourist destination and the centerpiece of Tokiwa Park, where greenery, flowers and sculptures abound.
Feudal lords proactively implemented new farm policies, however, farmers pleaded for the construction of an embankment for a lake at Tokiwa, which started in 1695 and was completed three years later. In addition, related work for the basin, irrigation channel and cadastral survey were completed in 1701 enabling approx. 440 hectares of paddy irrigation. The positioning of the embankment was divined by an old, white-haired oracle. When no water accumulated in the basin, he apparently planted pines along the edge and prayed to local Shinto and Buddhist deities.
Ube City, which flourished as a coal mining town, increased in population growing from a village in 1921 to a city almost overnight. This led to the purchasing of land from 1924 by local businessmen with the objective of making the scenic Lake Tokiwa area open to the public. The purchased tracts were then donated to the city and Tokiwa Park opened in 1925.
In 1943, efforts to improve irrigation from Lake Tokiwa led to the diversion of Kotogawa River to the lake turning it into a retarding basin and making its water available for industrial use. Because the lake was originally an artificially embanked reservoir with rainfall as its principal source of water, it was a pure freshwater lake. However, the water quality changed due to the introduction of water from Kotogawa River, pelican husbandry and its use as a habitat for waterfowl. Even now, there are over one hundred species of wild birds near the lake, which has become a mecca for birdwatchers.
Ube City, badly polluted with soot and dust from the post-war recovery, proposed citizen flower planting activities in the municipal park and implemented flowering drives to overcome adversity.