▁# 1 1 3 0 3 5 0 0 ▁at ▁Vern alis , ▁ ▁above ▁Su is un ▁Bay ▁and ▁ ▁below ▁the ▁mouth ▁of ▁the ▁Stanis laus ▁River , ▁the ▁average ▁dis charge ▁of ▁the ▁San ▁Jo aqu in ▁River ▁between ▁ 1 9 2 4 ▁and ▁ 2 0 1 1 ▁was ▁, ▁or ▁ 3 . 3 ▁million ▁a cre - fe et ▁( 4 . 0 ▁million ▁dam 3 ) ▁per ▁year . ▁The ▁highest ▁recorded ▁annual ▁mean ▁was ▁, ▁ 1 5 . 4 ▁million ▁a cre - fe et ▁( 1 9 . 0 ▁million ▁dam 3 ), ▁in ▁ 1 9 8 3 , ▁while ▁the ▁lowest ▁was ▁, ▁, ▁in ▁ 1 9 7 7 . ▁The ▁maximum ▁peak ▁flow ▁occurred ▁on ▁December ▁ 9 , ▁ 1 9 5 0 ▁at ▁, ▁and ▁a ▁low ▁flow ▁of ▁ ▁was ▁recorded ▁on ▁August ▁ 1 0 , ▁ 1 9 6 1 . ▁ ▁San ▁Jo aqu in ▁River ▁month ly ▁dis charg es ▁at ▁Vern alis ▁ ▁Ge ology ▁ ▁In ▁a ▁ge olog ic ▁context , ▁the ▁San ▁Jo aqu in ▁River ▁can ▁be ▁divided ▁into ▁two ▁major ▁segments . ▁The ▁upper ▁ ▁above ▁Fri ant ▁Dam ▁in ▁the ▁Sierra ▁is ▁character ized ▁as ▁a ▁ste ep - gradient , ▁rock y ▁mountain ▁stream . ▁Over ▁millions ▁of ▁years , ▁the ▁upper ▁San ▁Jo aqu in , ▁as ▁well ▁as ▁the ▁upper ▁reaches ▁of ▁most ▁of ▁its ▁trib ut aries , ▁have ▁er