Intensification of hydrological drought in California by human water management

He, X., Wada, Y. ORCID: https://orcid.org/0000-0003-4770-2539, Wanders, N., & Sheffield, J. (2017). Intensification of hydrological drought in California by human water management. Geophysical Research Letters 24 (4) 1777-1785. 10.1002/2016GL071665.

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Abstract

We analyze the contribution of human water management to the intensification and mitigation of hydrological drought over California using the PCR-GLOBWB hydrological model for the period 1979-2014. We demonstrate that considering water management results in more accurate discharge representation. During the severe 2014 drought, water management alleviated the drought deficit by ∼50% in Southern California through reservoir operation during low flow periods. However, human water consumption (mostly irrigation) in the Central Valley increased drought duration and deficit by 50% and 50-100%, respectively. Return level analysis indicates that there is more than 50% chance that the probability of occurrence of an extreme 2014-magnitude drought event was at least doubled under the influence of human activities compared to natural variability. This impact is most significant over the San Joaquin Drainage basin with a 50% and 75% likelihood that the return period is more than 3.5 and 1.5 times larger, respectively, because of human activities.

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