On January 17, 2014, California State Governor Jerry Brown declared a drought state of emergency. On April 2, 2017, Governor Brown lifted the drought emergency, but declared that California must continue water conservation efforts. With the official conclusion of the most recent drought, which spanned water years 2012 through 2016, it is timely to compare it with other historic California droughts and also to consider some of the lingering impacts.
Water year is defined as starting on October 1 of the preceding year and ending on September 30 of the water year (e.g. Water Year 2017 starts on October 1, 2016, and ends on September 30, 2017). Hydrologically, “water year” is a useful metric because the majority of precipitation in Western states occurs from late fall to early summer. Thus, water years are useful to delineate dry and wet periods.
California’s Historic Droughts
Drought is a prolonged and widespread deficit in available water supplies that may cause substantial economic or social impacts, or physical damage or injury to individuals, property, or the environment. These prolonged periods may include one or more years of near normal precipitation, if significant drought impacts continue during this time period. Considering this definition, droughts in California can be classified in four ways: