Due to the geographical condition of being surrounded by oceans and having steep mountains, Japan has many rivers with short length and fast flow and plenty of clear water in which toxic bacteria can hardly grow.
日本は周囲を大海に囲まれ山が多いという地理的条件から、全長が短く流れの速い川が多く、淀みなく流れ有毒な細菌が繁殖しにくい水に恵まれていた。