2011–17 California drought

From December 2011 to March 2017, the state of California experienced one of the worst droughts to occur in the region on record. The period between late 2011 and 2014 was the driest in California history since record-keeping began. 102 million trees died in total due to the drought from 2011 to 2016, with 62 million dead in 2016 only, according to the US Forest Service.

By February 23, 2017, the percentage of the state in drought was less than during the beginning of the drought in late 2011, mainly due to a very wet pattern caused by atmospheric river-enhanced Pacific storms. The wet pattern caused severe flooding.

In 2013 the total rainfall was less than 34% of what was expected. Many regions of the state accumulated less rainfall in 2013 than any other year on record. As a result of this, many fish species were threatened. Streams and rivers were so low that fish couldn't get to their spawning grounds, and survival rates of any eggs that were laid were expected to be low. Lack of rainfall had caused the mouths of rivers to be blocked off by sand bars which further prevented fish from reaching their spawning grounds. Stafford Lehr, Chief of Fisheries within the California Department of Fish and Wildlife said that 95% of winter run salmon didn’t survive in 2013.

According to the NOAA Drought Task Force report of 2014, the drought is not part of a long-term change in precipitation and was a symptom of the natural variability, although the record-high temperature that accompanied the recent drought may have been amplified due to human-induced global warming. This was confirmed by a 2015 scientific study which estimated that global warming "accounted for 8–27% of the observed drought anomaly in 2012–2014... Although natural variability dominates, anthropogenic warming has substantially increased the overall likelihood of extreme California droughts."

By February 1, 2014, Felicia Marcus, the chairwoman of the State Water Resources Control Board, claimed the 2014 drought "is the most serious drought we've faced in modern times." Marcus argues that California needs to "conserve what little we have to use later in the year, or even in future years." A 16-year study of how precipitation affects groundwater-dependent vegetation was conducted and the results showed that the alkali meadow vegetation plant community is groundwater dependent, and that this characteristic buffers the system from the effects of drought. This means that certain plants are actually able to help prevent droughts, but can only do so if groundwater is maintained at a certain level. One of the reasons that the study was conducted was to ascertain whether the Owens Valley region of California could handle any practiced or proposed groundwater extraction.

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