A drainage basin is the entire area drained by a river and its tributaries.
Drainage basin hydrological cycle
13.2 Drainage Basins – Physical Geology
Drainage Basins. - ppt video online download
What are the features of a drainage basin? - Internet Geography
13.2 Drainage Basins – Physical Geology
Drainage Basins
Geography 101 Online
Geographical map of drainage basin of Helmand River and Puzak
Drainage basin, WaterWiki
Purposes of reference conditions illustrated in a river basin