- indu ced , ▁as ▁from ▁le aking ▁fuel ▁t anks ▁or ▁to xic ▁chemical ▁sp ills . ▁P estic ides ▁and ▁fert il izers ▁applied ▁to ▁la wn s ▁and ▁cro ps ▁can ▁accum ulate ▁and ▁migr ate ▁to ▁the ▁water ▁table . ▁Le ak age ▁from ▁sept ic ▁t anks ▁and / or ▁waste - dis pos al ▁sites ▁also ▁can ▁introduce ▁b acter ia ▁to ▁the ▁water , ▁and ▁p estic ides ▁and ▁fert il izers ▁that ▁se ep ▁into ▁far med ▁soil ▁can ▁eventually ▁end ▁up ▁in ▁water ▁drawn ▁from ▁a ▁well . ▁Or , ▁a ▁well ▁might ▁have ▁been ▁placed ▁in ▁land ▁that ▁was ▁once ▁used ▁for ▁something ▁like ▁a ▁garbage ▁or ▁chemical ▁dump ▁site . ▁Pol l uted ▁run off ▁is ▁created ▁by ▁ra inf all ▁or ▁snow - m elt ▁moving ▁over ▁and ▁through ▁the ▁ground . ▁As ▁the ▁run off ▁moves , ▁it ▁pick s ▁up ▁and ▁car ries ▁away ▁natural ▁and ▁human - made ▁poll ut ants , ▁finally ▁depos iting ▁them ▁into ▁waters h eds ▁via ▁la kes , ▁rivers , ▁wet lands , ▁coast al ▁waters , ▁and ▁even ▁our ▁under ground ▁sources ▁of ▁drink ing ▁water . ▁In ▁ 2 0 0 2 , ▁in ▁the ▁National ▁Water ▁Qu ality ▁In ventory ▁report ▁to ▁U . S . ▁Congress , ▁the ▁states ▁reported ▁that ▁agricult ural ▁non - point ▁source ▁( N PS ) ▁poll ution ▁is ▁the ▁leading ▁cause ▁of ▁river ▁and ▁stream ▁imp air ment ▁and ▁the ▁second ▁leading