Translation:One day there will be wars because of water shortage.
"Someday there will be wars because of a water shortage." OR " because of a shortage of water." "Someday" and "one day" are interchangeable in meaning. "Because of water shortage" is incorrect. The article "a" is needed: "because of a water shortage" or "because of a shortage of water".
I don't think 'a' is needed. We're talking about the concept of water shortage. Not about a single occurrence of water shortage.