In regard to palaeoclimatic data tree rings, there was a drought history with some multidecadal aridity periods of California in the past 500 years and since 1900, there have been at least eight multiyear periods of low precipitation (Larsen et al. 2014). Woodhouse et al. 2009 argued that increasing dryness accompany with increasing temperatures relative to both instrumental records and palaeoclimatic records.
Long period droughts bring a large amount of losses to California. There is an economic impacts assessment of the year 2014 has been taken under the third driest year circumstance to estimate losses from dairies, crop production and livestock by using a set of models (Howitt et al. 2014). The summary table show as follow:
Table1 2014 Drought and California Agriculture Summary
In the context of worse drought situation, some effective measures should be taken into implement to relief the drought stress. Groundwater is really important in U.S., on which 60% of irrigation relies (Scanlon et al. 2012), however the situation of groundwater seems not very well (Figure1). While increasing water storage through managing extra surface water return to aquifers by up to 3 km3 exhibits hope for dealing with droughts and improving sustainability of groundwater resources in the Central Valley (Scanlon et al. 2012).
Figure1 Measured groundwater level changes from predevelopment (~1950) to 2007 in the high plain aquifer
In conclusion, recent droughts in California are not unparalleled and they might occur as warm-drought type. Droughts will cause a range of money losses, therefore some effective steps should be exerted to mitigate this worse situation.
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