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. 2016 Jun 27;113(28):7768–7773. doi: 10.1073/pnas.1600400113

Fig. 1.

Fig. 1.

Selected oil and gas fields and counties in California and the Central Valley shallow groundwater aquifer system extent (39). The Central Valley Subregions, as shown by the thicker boundary lines in blue, from north to south are Sacramento, Delta, San Joaquin, and Tulare (32).