▁Dam , ▁the ▁main ▁dam ▁on ▁the ▁San ▁Jo aqu in ▁River , ▁began ▁in ▁ 1 9 3 7 ▁and ▁was ▁completed ▁in ▁ 1 9 4 2 . ▁The ▁dam ▁serves ▁for ▁ir rig ation ▁and ▁flo od ▁control ▁storage , ▁but ▁its ▁main ▁purpose ▁is ▁to ▁di vert ▁water ▁into ▁the ▁Mad era ▁Canal , ▁which ▁runs ▁north west ▁along ▁the ▁San ▁Jo aqu in ▁Valley ▁to ▁the ▁Ch ow ch illa ▁River , ▁and ▁the ▁Fri ant - K ern ▁Canal , ▁which ▁car ries ▁San ▁Jo aqu in ▁water ▁all ▁the ▁way ▁south ▁into ▁the ▁Tul are ▁Bas in , ▁termin ating ▁at ▁the ▁K ern ▁River . ▁Both ▁are ▁ir rig ation ▁and ▁municipal ▁supply ▁can als ▁serving ▁primarily ▁agricult ural ▁interests . ▁Water ▁from ▁the ▁Fri ant ▁Dam ▁supplies ▁almost ▁ ▁of ▁far ml and ▁in ▁F res no , ▁K ern , ▁Mad era , ▁and ▁Tul are ▁count ies . ▁The ▁di version ▁of ▁water ▁off ▁the ▁San ▁Jo aqu in ▁at ▁Fri ant ▁Dam ▁leaves ▁little ▁more ▁than ▁a ▁trick le ▁below ▁the ▁dam ▁in ▁most ▁years , ▁except ▁for ▁releases ▁serving ▁far ms ▁in ▁the ▁immediate ▁area ▁down stream ▁of ▁Fri ant . ▁ ▁A ▁key ▁point ▁for ▁ir rig ation ▁water ▁distribution ▁on ▁the ▁San ▁Jo aqu in , ▁despite ▁its ▁small ▁size , ▁is ▁M end ota ▁Dam . ▁Bu ilt ▁in ▁ 1 8 7 1 ▁at ▁the ▁jun ct ure ▁of ▁the ▁San ▁Jo aqu in ▁River ▁and