In this lyric, "water" is used to describe the girl's appearance. In China culture, water is regarded as a symbol of purity and clarity, which can represent women and purity. Therefore, using "beauty as water" to describe the beauty of girls means that their looks are beautiful, soft and bright, like clear crystals.
In addition, water symbolizes life and vitality. In the lyrics, the girl in Alishan is described as full of vigor and vitality, like running water. This description also conveys the praise of life and respect for nature, and emphasizes the harmonious relationship between man and nature.
In short, the lyrics of "Alishan girl is as beautiful as water" express the praise of Alishan girl's beautiful face and reverence for nature with the element of "water" symbolizing purity, clarity, life and vitality.