The chart belowindicates Sonoma County Water Agency’s contractor water purchases from Russian River over the months of June through September for five years (2008-2012). Numbers represent acre feet for four month period.
Unfortunately, it is impossible to explain what percent of any decreases in water use were a result of conservation, since many of the contractors turned to ground water and/or other local sources to compensate for taking less water from river. There may also be other occupancy and use factors that account for lower use. In general, summer use represents about half of the water sold for the year since that is when most people water their gardens.
2010 through 2012 were normal flow years, mostly due to late spring rains. It is not clear why 2011 saw much lower use by Santa Rosa, Petaluma, North Marin, and Cotati, than 2010 and 2012. 2009 was considered a Dry Year that went to Critical Dry Year in August (this triggers lower minimum flows).