Higher Temperatures Will Shrink California’s Water Supply

Even if California gets the same amount of rain and snow in the future, higher temperatures will lead to more evaporation and the need to leave more water in rivers to meet water quality standards. For each degree of warming, the amount of water delivered by California’s State Water Project and Central Valley Project through the Sacramento-San Joaquin Delta is expected to decline.

Change in Average Temperature (Degrees C)
Percent change in water supply
+0.5º (+0.9ºF) -4.2%
+1º (+1.8ºF) -6.2%
+2º (+3.6ºF) -14.5%
+3º (+5.4ºF) -19.4%
+4º (+7.2ºF) -23.6%