(Rivers are normally marked blue on a map.) So what does a black colored river on a map indicate ?

Question

(Rivers are normally marked blue on a map.) So what does a black colored river on a map indicate ?

Answer 1

Man-Made

Answer 2

Since most borders of states, countries, provinces, etc. follow natural barriers such as rivers.  The black line may represent the political border on your map that just happens to also be a river.

Answer 3

Seasonal river i guess.

Answer 4

they are not so important rivers

Answer 5

Thats a good question.  Four answers before me and all are different; and all are reasonable answers.  I had my own suggestion, too... there are salt and fresh water lakes, are there not salt and freshwater rivers?