▁lack ▁of ▁river ▁boat ▁traffic ▁and ▁the ▁def or est ation ▁of ▁the ▁u pl and ▁areas ▁in ▁what ▁is ▁now ▁the ▁Upper ▁Mar ik ina ▁River ▁Bas in ▁Prote cted ▁Land s cape ▁contributed ▁to ▁the ▁river ' s ▁s ilt ation , ▁further ▁reducing ▁its ▁value ▁as ▁a ▁transport ▁route . ▁ ▁Due ▁to ▁neg lig ence ▁and ▁industrial ▁development , ▁the ▁river ▁has ▁become ▁very ▁poll uted , ▁an ▁act ▁which ▁recent ▁Mar ik ina ▁City ▁administr ations ▁have ▁attempted ▁to ▁address . ▁ ▁The ▁Mar ik ina ▁River ▁system ▁ ▁In ▁the ▁Pam it in an ▁Prote cted ▁Land s cape ▁located ▁in ▁Sit io ▁W awa , ▁Br gy . ▁San ▁Rafael ▁in ▁Rod rig uez , ▁the ▁Mar ik ina ▁River ▁is ▁dam med ▁by ▁W awa ▁Dam , ▁a ▁structure ▁built ▁during ▁the ▁early ▁ 1 9 0 0 s ▁to ▁provide ▁water ▁for ▁Man ila . ▁From ▁Rod rig uez , ▁the ▁river ▁flows ▁through ▁San ▁Mate o ▁then ▁to ▁its ▁names ake ▁city ▁of ▁Mar ik ina . ▁In ▁Pas ig ▁City , ▁the ▁river ▁meets ▁the ▁gates ▁of ▁the ▁Mang g ah an ▁Flo od way , ▁a ▁controlled ▁water way ▁used ▁to ▁prevent ▁flo oding ▁in ▁Man ila ▁during ▁heavy ▁ra ins ▁by ▁diver ting ▁most ▁of ▁the ▁water ▁of ▁the ▁Mar ik ina ▁towards ▁Lag una ▁de ▁bay ▁instead ▁of ▁Pas ig ▁River . ▁Loc ated ▁ ▁down stream ▁is ▁the ▁confl u ence ▁of ▁Mar ik ina ▁and ▁Pas ig