( ( The ( vertical flow ) ) ( ( is ( when ( ( ( ( is slowly ) ( seeps ( into ( the ground ) ) ) ) and ) ( is ( called infiltration ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ vertical) (NN flow)) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (VP (VP (VBZ is) (ADVP (RB slowly)) (ADJP (JJ seeps) (PP (IN into) (NP (DT the) (NN ground))))) (CC and) (VP (VBZ is) (VP (VBN called) (NP (NN infiltration)))))))) (. .)))
The vertical flow is when is slowly seeps into the ground and is called infiltration .
(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))))) (. .)))