What are the ways to increase the amount of water on Earth? Which of them are applicable in Siberia?

None of the currently known methods, man can violate the quantitative characteristics of substances on the planet. After all, the laws of conservation of mass – nothing is taken from nowhere and disappears into nowhere. So to increase the amount of fresh water, you can take salt from the ocean water, but with rains the water will return to the salty ocean, becoming salty again. The only way is to get water from outside the Earth, but you rarely find water on other planets, especially since this method will not be reasonable and very expensive.