( Infiltration ( ( occurs ( when ( precipitation ( seeps ( into ( the ground ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Infiltration)) (VP (VBZ occurs) (SBAR (WHADVP (WRB when)) (S (NP (NN precipitation)) (VP (VBZ seeps) (PP (IN into) (NP (DT the) (NN ground))))))) (. .)))
Infiltration occurs when precipitation seeps into the ground.
(ROOT (S (NP (NP (NNP Water)) (VP (VBG seeping) (PP (IN into) (NP (DT the) (NN ground))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (NN infiltration))))) (. .)))