( ( ( ( The ( land area ) ) ( that ( drains ( ( ( rain and ) snow ) ( melt ( to ( a river ) ) ) ) ) ) ) ( is ( called ( a watershed ) ) ) ) ( , ( ( ( each tributary ) ( to ( the river ) ) ) ( ( is ( part ( of ( a ( smaller watershed ) ) ) ) ) . ) ) ) )
(ROOT (S (S (NP (NP (DT The) (NN land) (NN area)) (SBAR (WHNP (WDT that)) (S (VP (VBZ drains) (S (NP (NN rain) (CC and) (NN snow)) (VP (VB melt) (PP (TO to) (NP (DT a) (NN river))))))))) (VP (VBZ is) (VP (VBN called) (NP (DT a) (NN watershed))))) (, ,) (NP (NP (DT each) (NN tributary)) (PP (TO to) (NP (DT the) (NN river)))) (VP (VBZ is) (NP (NP (NN part)) (PP (IN of) (NP (DT a) (JJR smaller) (NN watershed))))) (. .)))
The land area that drains rain and snow melt to a river is called a watershed, each tributary to the river is part of a smaller watershed.
(ROOT (S (NP (NP (DT All)) (PP (IN of) (NP (NP (DT the) (NN land)) (VP (VBN drained) (PP (IN by) (NP (DT a) (NN river) (NN system))))))) (VP (VBZ is) (VP (VBN called) (NP (NP (PRP$ its) (NN basin)) (, ,) (CC or) (NP (DT the) (`` ``) (JJ wet) ('' '') (NN term) (NN watershed)))))))