California governor Jerry Brown declared a drought state of emergency in January 2014, following years of wintertime rainfall levels dipping below historic averages. A lack of rainfall throughout 2015—precipitation was 20% below average—sustained the drought. Surface water levels got so low that residents had to increasingly tap into groundwater resources in order to meet agricultural, urban, and industrial needs. This usage put immense pressure on groundwater resources and made it extremely difficult to manage water resources across the state.