Musannaf Ibn Abi Shayba 1:461

Ubayd Allah ibn Musa narrated to us, from Yazid ibn Ibrahim, who said: Qatadah was asked about water that has developed an odor, whether one may perform ablution with it. He said: There is no harm in *al-turuq* water and *al-ranaq* water. He said: *Al-turuq* is that which the beasts of burden tread upon and wade through, and *al-ranaq* is that which has developed an odor.