( ( ( ( Water ( returns ( to ( ( the Earth ) ( from ( precipitation ( falling ( on ( ( ( the land ) , ) ( ( where gravity ) ( either ( ( takes it ) ( into ( ( the ground ) ( as infiltration ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) or ) ( it ( begins ( ( running downhill ) ( as ( surface runoff ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Water)) (VP (VBZ returns) (PP (TO to) (NP (NP (DT the) (NN Earth)) (PP (IN from) (NP (NP (NN precipitation)) (VP (VBG falling) (PP (IN on) (NP (NP (DT the) (NN land)) (, ,) (SBAR (WHNP (WHADVP (WRB where)) (NN gravity)) (S (ADVP (RB either)) (VP (VBZ takes) (NP (PRP it)) (PP (IN into) (NP (NP (DT the) (NN ground)) (PP (IN as) (NP (NN infiltration))))))))))))))))) (CC or) (S (NP (PRP it)) (VP (VBZ begins) (S (VP (VBG running) (ADVP (RB downhill)) (PP (IN as) (NP (NN surface) (NN runoff))))))) (. .)))
Water returns to the Earth from precipitation falling on the land, where gravity either takes it into the ground as infiltration or it begins running downhill as surface runoff .
(ROOT (S (NP (NNP Precipitation)) (VP (VBP are) (NP (NP (DT a) (JJ natural) (NN process)) (SBAR (WHNP (WDT that)) (S (VP (VBZ allows) (NP (NN water)) (S (VP (TO to) (VP (VB return) (ADVP (RB again)) (PP (TO to) (NP (NP (DT the) (NN earth) (POS 's)) (NN surface))))))))))) (. .)))