Is it makruh to urinate in water even if it’s a flowing stream or river?
It is bad manners to urinate in stagnant water and similarly it is makruh do so in flowing water. There is no benefit in trying to find an exception to this rule and what the Shariah says is exempt from this. It is mentioned in Mujtaba that irrespective of whether the water is less or a lot, stagnant or flowing, it is makruh to urinate in it. Imam Abu Hanifa called the person who urinates in flowing water an ignorant.
And Allah ﷻ knows the best
Imam Ahmad Rida Khan رحمة الله تعالى عليه
Translation by Dr Musharraf Hussain Al-Azhari Translator of Majestic Quran, www.majesticquran.co.uk