First, I would change it to "Nowadays, many people in different parts of the world are facing the fact that water is insufficient to satisfy human needs." Second, the sentence doesn't quite make sense as written. People have always known that water is insufficient to satisfy human needs. We need food. Arguably we need clothing and shelter. According to the Beatles, all we need is love. I think you might mean something closer to "Nowadays, many people in different parts of the world are facing the fact that the water supply is insufficient to satisfy humanity's needs."

I think you should write " ...are facing up to..." nowadays go with present continuous tense

Nowadays is used correctly. I would say ... are faced with the fact.... or have been faced with the fact. Facing the fact is correct but not facing "with" the fact.