Pure water comes  from the hemisphere and cycle / evaporates to clouds , and back in the hemisphere.  All the water on earth is in constant circulation known as the hydrological cycle. Water is evaporated from variety of places, transpiring largely from the ocean, rivers, lakes, plants in large forest, soil, snow from mountains. Evaporation is greater in the ocean( large body of water ), and large forest.

Carboniferous period,~ 350 million years ago, earth had twice the amount of carbon dioxide in the atmosphere.  Plant evolution, now large forests and tall trees have removed carbon dioxide in the atmosphere, and stored in trees  trunk/ leaves and soil.

On earth trees are vascular plants, because they absorb rain water, and they are very tall.  Trees store the purest water,  such as baobab, cactus.   Forest recycle elements in the soil, and keep ground water clean and pure.  River water remains clean surrounding trees.

There are different processes and cycle for water conservation In every region, tropical, temperate, desert, tundra. Ice in the polar region absorbs radiation, thus regulates the climate, reducing carbon from melting ice.   

Rajwantee, WA, USA