Fig. 7: Proportional contribution of large rivers, surface water, and precipitation sources versus depth.

(a) Model 1, (b) model 2, and (c) model 3. The purple, blue, and orange lines are the moving depth average of 200 groundwater samples. The purple, blue, and orange-shaded regions are the corresponding interquartile range. The standard error associated with the moving depth average is less than <0.03, and for this purpose, clarity has been omitted from the figure. The dashed gray line at 100 m roughly differentiates between modern and late Holocene recharged water (0–100 m depth) with early Holocene and Pleistocene water (100–250 m depth). Please refer to Fig. S5 for the full statistical distribution of standing water for model 2. See Supplementary Notes 2 on the limitations of using modern endmember values for late Holocene–Early Pleistocene recharged deep waters.