Hydrogen vs. Battery Electric Cars

One factor that I really concern about hydrogen electric vehilces (HEV): the hydrogen itself. 
Ok, we get that from electrolysis, which is less dangerous, and expensive than mining lithium. Ok, that is cyclical which is far better than consuming lithium (even in long term). 
But we speaking here about changing the entire world mobility (and even implied in the video the electricity too) from fossil fuel. The water on the planet is constant (more or less). There were no more water 100Ky ago and won't be 100Ky later either. If the entire population (estimated in 10B people) use HEVs for personal, public, and cargo transport, using hyrogen cells to phones, power grid, etc., where all the water go? I did not do the math yet, but that is a lot of water. Maybe the melting ice caps covers the excess water.. There is another big issue too. Hydrogen burn into water, so fortunately the absolute mass of water is not changing. But that is pure water, just H2O. That is useless from the invironment. Living things needs the minerals and microelements from the water. If I drink pure destilled water I will die from dehydration. 
We will need depurification plants to use that water again in the environment, which means the cyclical energy using is not cyclical anymore, and probably needs more energy to depurifying the water. Or we just take an enormous amount of water from the Earth hydrosphere which could (well, most definitely will) cause catastrphic environmental impacts.
Long story short: HEVs are better for the environment than BEVs, but still not a solution in my opinion.