▁major ▁trib ut aries ▁of ▁Lag una ▁de ▁Bay ▁and ▁is ▁regularly ▁monitor ed ▁by ▁the ▁Lag una ▁Lake ▁Development ▁Author ity ▁( LL DA ) ▁through ▁one ▁of ▁its ▁ 1 5 ▁river ▁monitoring ▁stations . ▁ ▁Al ong ▁with ▁the ▁San ▁Crist ob al ▁River , ▁it ▁is ▁one ▁of ▁the ▁two ▁major ▁rivers ▁of ▁Cal amba ▁that ▁dra ins ▁into ▁Lag una ▁de ▁Bay . ▁Its ▁waters hed ▁area ▁covers ▁Cal amba ▁City ▁in ▁Lag una ▁and ▁the ▁municipal ities ▁of ▁Santo ▁Tom as , ▁Tan au an , ▁and ▁Mal var ▁in ▁Bat ang as . ▁ ▁Mon itor ing ▁and ▁Conserv ation ▁ ▁In ▁the ▁December ▁ 2 0 0 5 ▁LL DA ▁Water ▁Qu ality ▁Status ▁Report , ▁the ▁San ▁Juan ▁River ▁was ▁listed ▁as ▁" wor se ▁than ▁Class ▁D " ▁with ▁a ▁very ▁low ▁percentage ▁of ▁dissol ved ▁o xygen ▁s atur ation . ▁It ▁also ▁indicated ▁that ▁this ▁status ▁had ▁not ▁improved ▁since ▁the ▁river ▁had ▁last ▁been ▁monitor ed . ▁ ▁According ▁to ▁the ▁Department ▁of ▁Environment ▁and ▁Natural ▁Resources ' s ▁Water ▁Us age ▁& ▁Classification ▁for ▁F resh ▁Water , ▁Class ▁D ▁fresh water ▁is ▁suitable ▁for ▁agricult ure , ▁ir rig ation , ▁liv est ock ▁water ing ▁and ▁industrial ▁water ▁supply ▁class ▁II . ▁" W or se ▁than ▁Class ▁D " ▁means ▁that ▁the ▁San ▁Juan ▁is ▁not ▁us able ▁for ▁any ▁of ▁these ▁functions . ▁ ▁The ▁LL DA ' s ▁conservation ▁efforts ▁for ▁the ▁major ▁trib