China won't disrupt India's water supply. Even if both nations go to war, this is a step way too far. The Americans would include something this evil in their playbook since they have waged energy and food warfare in the past. India doesn't really depend on those rivers for drinking water. India isn't threatening to disrupt China's sources of water. Unless they have done something that despicable, there is no precedence or justification in engaging India in any sort of direct asymmetric warfare.
Since this issue with India began, China has done very little to India. No trade war against it (despite India attempting this), no sanctions or bans on produce that are actually supporting India's daily function, not even igniting Pakistan India tensions (in fact the opposite has happened). No arming of Pakistan or other groups which work against India's political establishment. Outside of one isolated and relatively harmless cyber attack, possibly done to serve as a warning and demonstration of ability to cripple India's grid, China has largely been very agreeable and passive in confronting India. It doesn't need to be any more. India has largely been harmless even if their intentions are greater than their abilities. Until India translates imagined and intended ills into damaging action, China will not engage. To consider something like controlling the flow of rivers, require India to have done a lot of actual damage to China. I believe China would start with arming and directing rebel groups and hurt India at its pocket. It hasn't even come to that despite India having tried to hurt China's wallet and attempt to instigate social division along with the US.
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