Comment by cogman10

The problem is that while there is a lot of water available, more than our needs, we do not use water efficiently. In particular, food production is horribly wasteful with water. Even small farms will dump 100s of gallons of water per minute (yes minute) onto the ground to ultimately be washed away or evaporated.

What that means is that the piping to get enough water everywhere is enormous. The global usage was 2 quadrillion gallons of water. [1]

There are ways to use water much much more efficiently, but they are expensive to implement. Hydroponics can grow a lot of food, but it requires a lot of power and infrastructure to get setup.

[1] https://www.htt.io/learning-center/water-usage-in-the-agricu...