I think the worlds water problems could be solved by a process called desalination. That is taking ocean water or salt water and running it through a process which strips the salt out of the water turning it into fresh water. As of now the process is not very energy efficient, but I believe that can and will change in the near future. With 1% of the worlds population depending on desalinated water for daily needs, it is only a mater of time before more energy efficient means are attained. Ground water and clean rivers are the way to go right now but these sources are not always available to all parts of the planet. And desalinated water is actually healthier than most fresh water sources by containing less salt and limescale in it.
As of 2015 18,426 desalination plants operated worldwide, providing over 300 million people with fresh clean water. If we can keep things progressing to allow more and more desalination plants where they are needed and that are ever more energy efficient we could ultimately one day have fresh water for everyone on this planet.
(Graphics sourced from google, picture taken by me)
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