Prove to me that there is any less water (including glaciers, ice caps, etc.) than there has been, say 50 years ago, 100 years ago, one million years ago...and we might talk. It might be distributed differently, it might be fresh or salty, but the water is still there.
Where this bullshit will be 'sold' to people is in areas where there are high density populations which exceed the natural carrying capacity of their resources. Aquifer drawdowns and fresh water usage in those areas (where, incidentally, roughly half of the population lives), and the destruction of reservoirs which formerly guaranteed adequate supplies in drier years, will be used to push this garbage among the urbanites, who will vote with their limited knowledge to enslave themselves further.