( They ( ( form ( ( the headwaters ) ( for ( the ( Delta River ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP form) (NP (NP (DT the) (NNS headwaters)) (PP (IN for) (NP (DT the) (NNP Delta) (NNP River))))) (. .)))
They form the headwaters for the Delta River.
(ROOT (S (NP (NNP Delta)) (VP (VBZ is) (NP (NP (DT a) (NN triangular) (NN feature)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (NN river)) (VP (VBZ empties) (PP (IN into) (NP (NP (DT a) (JJ large) (NN body)) (PP (IN of) (NP (RB still) (NN water)))))))))))))) (. .)))