▁syn onymous ▁with ▁the ▁San ▁Jo aqu in ▁Valley , ▁and ▁is ▁bounded ▁by ▁the ▁Sierra ▁Nev ada ▁to ▁the ▁east , ▁the ▁Coast ▁R anges ▁on ▁the ▁west , ▁and ▁the ▁Te h ach api ▁Mountains ▁on ▁the ▁south . ▁ ▁The ▁San ▁Jo aqu in ▁Valley ' s ▁major ▁sout heast - n orth west ▁axis ▁runs ▁roughly ▁parallel ▁with ▁the ▁Pacific ▁coast ▁of ▁California ; ▁it ▁measures ▁ ▁covering ▁all ▁or ▁parts ▁of ▁sevent een ▁California ▁count ies ▁stretch ing ▁from ▁north ▁of ▁L odi ▁to ▁well ▁south ▁of ▁B akers field . ▁Most ▁of ▁the ▁elev ation ▁change ▁in ▁the ▁San ▁Jo aqu in ▁occurs ▁within ▁the ▁first ▁ ▁above ▁Fri ant ▁Dam . ▁Its ▁highest ▁head w aters ▁are ▁at ▁over ▁, ▁but ▁by ▁the ▁time ▁the ▁river ▁reaches ▁the ▁fo oth ills , ▁it ▁is ▁a ▁mere ▁ ▁above ▁sea ▁level . ▁ ▁On ▁the ▁west ▁and ▁north west , ▁the ▁San ▁Jo aqu in ▁waters hed ▁borders ▁those ▁of ▁rivers ▁dra ining ▁into ▁the ▁Pacific , ▁while ▁beyond ▁almost ▁all ▁of ▁the ▁other ▁div ides ▁lie ▁end or he ic ▁bas ins , ▁mostly ▁of ▁the ▁Great ▁Bas in . ▁To ▁the ▁north , ▁a ▁low ▁series ▁of ▁rid ges ▁separ ates ▁the ▁San ▁Jo aqu in ▁River ▁bas in ▁from ▁that ▁of ▁the ▁Sac r amento ▁River . ▁The ▁Coast ▁R anges ▁bound ▁the ▁waters hed ▁on ▁the ▁west ▁and ▁borders ▁on ▁the ▁d rain ages ▁of ▁the ▁P aj aro ▁River , ▁Sal inas