What is the ruling regarding the purity of running water?

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Running water is considered pure unless it becomes changed. The default state of water is purity, and there is no established text or consensus declaring running water impure under normal circumstances. This is supported by the general principle that water is pure and is not rendered impure by anything, except that which overcomes its scent, taste, or color. The statement regarding water volume, "If the water reaches two qullahs, it does not carry impurity," is evidence for its purity, as the entire body of flowing water often reaches this volume and therefore does not carry impurity. Applying the two-qullah measure to a specific stream segment without evidence is arbitrary. Furthermore, the hadith concerning the two qullah measure primarily addresses stagnant water, and a valid analogy cannot be drawn to running water due to the latter's strength derived from its flow and connection to its source. The hadith intrinsically indicates that water reaching two qullahs is pure, and the logical implication (mafhum) suggests that water below this measure differs from it. This difference is established by distinguishing between running and stagnant water regarding impurity contamination, a distinction absent for water exceeding two qullahs.