Surface Water Classification and Water Quality Standards Article 5
If a terrestrial surface water body meets relevant environmental standards after treatment or natural purification, the classification and relevant environmental standards of the water body shall not be downgraded.
中文原文 地面水體分類及水質標準第5條
陸域地面水體經自淨或整治後達到相關環境基準時，即不得降低其水體分類及相關環境基準值。