4 %, ▁and ▁urban ▁areas ▁occupied ▁ 2 . 4 % ▁as ▁of ▁ 1 9 9 5 . ▁The ▁bas in ' s ▁main ▁population ▁cent ers ▁are ▁in ▁the ▁north ▁and ▁south ▁and ▁population ▁density ▁generally ▁increases ▁from ▁west ▁to ▁east . ▁In ▁fact , ▁despite ▁the ▁relatively ▁small ▁percentage ▁of ▁developed ▁areas , ▁more ▁than ▁ 5 0 % ▁of ▁the ▁population ▁lives ▁in ▁the ▁waters hed ' s ▁four ▁largest ▁cities : ▁F res no , ▁B akers field , ▁Stock ton ▁and ▁Mod esto . ▁ ▁Trib ut aries ▁Seven ▁major ▁trib ut aries ▁flow ▁directly ▁into ▁the ▁San ▁Jo aqu in ▁River , ▁all ▁of ▁which ▁run ▁from ▁the ▁Sierra ▁Nev ada ▁west wards ▁into ▁the ▁main ▁stem . ▁In ▁addition , ▁some ▁of ▁the ▁dis charge ▁of ▁the ▁Kings ▁River ▁also ▁enters ▁the ▁San ▁Jo aqu in ▁directly ▁( but ▁season ally ) ▁through ▁a ▁distrib ut ary . ▁Of ▁these , ▁the ▁Tu ol um ne ▁River ▁is ▁the ▁largest ▁in ▁any ▁respect : ▁longest , ▁greatest ▁d rain age ▁bas in , ▁and ▁highest ▁dis charge . ▁The ▁Mer ced ▁River ▁is ▁the ▁second ▁largest ▁by ▁length ▁and ▁d rain age ▁bas in , ▁but ▁the ▁M ok el um ne ▁River ▁has ▁a ▁greater ▁flow . ▁Trib ut aries ▁are ▁listed ▁below ▁proceed ing ▁from ▁the ▁mouth ▁up stream , ▁with ▁their ▁respective ▁main - st em ▁length , ▁waters hed ▁and ▁dis charge ▁noted . ▁R ivers ▁of ▁the ▁Tul are ▁Bas