Despite the booms and busts in rain fall over the 2001 through 2017 period, we find that state-wide water use is conservative, compared to the variability in rainfall. Nor do we detect that state-wide evaporation is increasing as the climate has warmed over this period. We find that crops use less water than conventional wisdom because fields are often fallow, but forests use more water than conventional wisdom because they have a long growing season and absorb more energy. We also find that interannual evaporation of native oak woodlands is closely tied to the depth of the water table, which is a function of the distant snow pack on the Sierra Nevada mountains.
Our intent is to provide water managers with new information on water use to better share water among the various stakeholders, e.g. agricultural, cities, fish, ground water reservoirs and water quality.