In 1936, the Japanese who then occupied Formosa built a dam and then cut through the mountains, bringing in the water from the nearby river. That's the only way Sun Moon Lake got to its current depth of 30 meters plus a 70 % increase in area over the original pond there.
民國廿三年時，日本人築起水壩、鑿穿山壁，引入旁邊河水，日月潭才有了今日水深卅公尺的規模，面積也較原來增加了百分之七十。