Other wars.
Following the terrorist attack in Kashmir India is threatening to divert the river Indus tributaries to punish Pakistan. China has built dams on tributaries of the Brahmaputra so could do the same to India. China and Pakistan are allies and all three are nuclear powers.
There is a climate element to all this as well. Water is King, without it we die.
The Sahel is a case in point. If Sudan and Ethiopia dam the Nile then Egypt will react - war! We will get wars.
Then there are the forests and arable lands. We are losing millions of hectares of them to do what? Provide food: no? We need to rape the Earth's minerals so that we can go on unsocial media, have a camera doorbell, "stream" things we never watch, pootle about in a battery car...
Countries will do whatever they can to feed and water their populations and if that means war then so be it. We are heading there.