▁" f oss il ▁water ", ▁and ▁is ▁real ist ically ▁non - ren ew able . ▁Norm ally , ▁ground water ▁is ▁util ized ▁where ▁surface ▁sources ▁are ▁un available ▁or ▁when ▁surface ▁supply ▁distribution ▁is ▁limited . ▁ ▁R ivers ▁sometimes ▁flow ▁through ▁several ▁countries ▁and ▁often ▁serve ▁as ▁the ▁boundary ▁or ▁dem arc ation ▁between ▁them . ▁With ▁these ▁rivers , ▁water ▁supply , ▁allocation , ▁control , ▁and ▁use ▁are ▁of ▁great ▁consequence ▁to ▁surv ival , ▁quality ▁of ▁life , ▁and ▁economic ▁success . ▁The ▁control ▁of ▁a ▁nation ' s ▁water ▁resources ▁is ▁considered ▁vital ▁to ▁the ▁surv ival ▁of ▁a ▁state . ▁Similar ▁cross - border ▁ground water ▁flow ▁also ▁occurs . ▁Compet ition ▁for ▁these ▁resources , ▁particularly ▁where ▁limited , ▁have ▁caused ▁or ▁been ▁add itive ▁to ▁conflicts ▁in ▁the ▁past . ▁ ▁The ▁high lands ▁of ▁Eth iop ia ▁may ▁be ▁considered ▁a ▁water ▁tower ▁region ▁in ▁East ▁Africa . ▁S over eign ▁control ▁of ▁u pl and ▁water ▁supply ▁is ▁likely ▁to ▁govern ▁down stream ▁politics ▁for ▁many ▁years . ▁ ▁Cont am ination ▁from ▁human ▁activity ▁ ▁Water ▁cont am ination ▁usually ▁occurs ▁through ▁a ▁series ▁of ▁two ▁mechan isms : ▁point ▁and ▁non - point ▁sources ▁of ▁poll ution . ▁According ▁to ▁the ▁U . S . ▁Environment al ▁Prote ction ▁Agency ▁( E PA ), ▁point ▁source ▁poll ution ▁is ▁" any ▁single ▁ident ifiable ▁source ▁of ▁poll ution ▁from ▁which ▁poll ut ants ▁are ▁dis charg ed ,