▁Mad den ▁Dam ▁The ▁upper ▁Ch ag res ▁River , ▁its ▁waters hed , ▁and ▁the ▁waters hed ▁of ▁several ▁trib ut aries ▁lie ▁within ▁the ▁Ch ag res ▁National ▁Park , ▁created ▁in ▁ 1 9 8 5 ▁to ▁preserve ▁the ▁habitat ▁and ▁flow ▁of ▁water ▁into ▁the ▁canal . ▁The ▁terrain ▁of ▁the ▁upper ▁Ch ag res ▁waters hed ▁is ▁rug ged , ▁with ▁its ▁mountain ▁s lop es ▁exceed ing ▁ 4 5 ▁degrees ▁in ▁ 9 0 ▁percent ▁of ▁its ▁territory . ▁Some ▁ 9 8 ▁percent ▁of ▁the ▁park ▁consists ▁of ▁old - g row th ▁tropical ▁forest . ▁ ▁The ▁upper ▁Ch ag res ▁and ▁its ▁seven ▁trib ut aries ▁flow ▁into ▁Lake ▁A la j uela ▁( former ly ▁Mad den ▁Lake ), ▁the ▁res er voir ▁created ▁by ▁the ▁Mad den ▁Dam . ▁As ▁these ▁rivers ▁contribute ▁ 4 5 ▁percent ▁of ▁the ▁total ▁water ▁for ▁the ▁canal , ▁the ▁lake ▁is ▁an ▁essential ▁part ▁of ▁the ▁waters hed ▁of ▁the ▁canal ▁zone . ▁The ▁lake ▁has ▁a ▁maximum ▁level ▁of ▁ ▁above ▁sea ▁level , ▁and ▁can ▁store ▁one ▁third ▁of ▁the ▁canal ' s ▁annual ▁water ▁requirements ▁for ▁the ▁operation ▁of ▁the ▁lo cks . ▁ ▁Lake ▁A la j uela ▁is ▁not ▁part ▁of ▁the ▁navig ational ▁route , ▁so ▁there ▁are ▁fewer ▁restrictions ▁on ▁its ▁water ▁level ▁than ▁for ▁G at un ▁Lake . ▁ ▁Water ▁from ▁the ▁res er voir ▁is ▁also ▁used ▁to ▁generate ▁hydro elect ric ▁power ▁and