We're not quite there yet, but we will be in a few more years.
It will likely kick off with China against Russia. See, China is also in the midst of a massive years long drought, and just on the other side of Mongolia is the largest freshwater lake on the planet.
China actually had a bottling plant being built on the shores of the lake until Russia said no.
Hell, Eastern Russia has a lot of resources that China really needs. So while the two countries are currently allies, the alliance is an uneasy one.