providing {HEAD ~ a source} of {TAIL ~ water} for flowing through a floway, said water containing a quantity of pollutants and having a pH lower than a pH of precipitation of said pollutants on entry into said floway 
of
providing { HEAD ~ a source } of { TAIL ~ water } for flowing through a floway , said water containing a quantity of pollutants and having a pH lower than a pH of precipitation of said pollutants on entry into said floway
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH