A hydrological system of unknowns

[Malequinn]

Good day,

What is the best way to name a hydrological system, i.e. a river flowing over 200km with no tributaries, just as an outlet of the Okavango Delta. The river makes several nearly right angle turns along the way. This is mainly because faults in the region influence the river. The conventional model of catchment delineation does not apply as the area is relatively very flat. No one has ever delineated it. 

I think calling it a hydrological system may work.....what do you think ?

Another one, the river, can dry for over 20 years and flow for another 20 years. What do you call such a river? 

Thank you

Malequinn