A-through an optimistic viewpoint.
I'm pretty sure it's railroads, because there's not that many highways in Siberia, the rivers would be frozen over, and there's not a ton of people in Siberia. I'm sorry if I'm wrong.
Answer:
Around the world the most significant restriction on access to potable water is money. While access to raw water sources, clean or otherwise, is important, the purification process itself is expensive. Once water has been rendered potable, it is important that it be delivered without reintroducing contamination.
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