What's the difference between 江 and 河? My daily newsletter contained the following sentence:

长江是中国最长的河。


According to the dictionary, 江 and 河 both mean "river", but they seem to be used differently.

Am I right in assuming that 长河是中国最长的江 is wrong (even if we assume that there is a river called 长河)? Is there a semantic difference?
江 is mostly used in the South; 河 is mostly used in the North. There are exceptions,  such as 黑龙江, 浏阳河.
Scale. 江 is exclusively for mighty rivers; 河 can be used for both large and small rivers.
All foreign rivers are named with 河.
There is no fundamental differences between 河 and 江.
江 is used for rivers whose banks are steep cliffs; 河 is used for rivers with beaches.
In some classic text, 江 refers to Yangtze river; 河 refers to Yellow River; the other rivers are named with 水, e.g. 渭水


Source: http://baike.baidu.com/subview/20655/8126542.htm#2