Sources

 "Unique body of water." Black Sea Scene. n.d. Web. 5 Dec. 2013. <http://www.blackseascene.net/content/content.asp?menu=0040032_000000>. 

What does positive water balance mean?

The positive water balance means the influx of water is balanced by an outflow of water. The Black sea has a positive water balance which means that it receives more freshwater from the rivers and rainfall than it loses from evaporation.