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Global Patterns of Groundwater Table Depth

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Science  22 Feb 2013:
Vol. 339, Issue 6122, pp. 940-943
DOI: 10.1126/science.1229881

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  • RE: updated dataset for Global Patterns of Groundwater Table Depth, Science, 339 (6122): 940-943, doi:10.1126/science.1229881, by the authors
    • Ying Fan, Professor, Rutgers University - New Brunswick
    • Other Contributors:
      • Gonzalo Miguez-Macho, Professor, Universidade de Santiago de Compostela

    Regarding: Global Patterns of Groundwater Table Depth, Science, 339 (6122): 940-943, doi: 10.1126/science.1229881

    Given the continued downloads and applications of our earlier model estimates of the global patterns in groundwater table depth (1), here we make available to the readers our recently revised estimates, and suggest that future applications use this new dataset, which is substantially different from the earlier estimates.

    The groundwater recharge in the earlier model (1) was from model-estimated mean annual groundwater recharge (2) based on top-2m vertical soil water balance: precipitation minus evapotranspiration (P-ET). It did not account for (a) lateral convergence among grid cells, (b) plant root uptake of soil water below 2m depth or groundwater, and (c) seasonal dynamics. The consequences are several but all resulted in a biased-high estimate of the water table (too shallow). First, without lateral flow from wetter uplands to drier lowlands in the recharge model (2), ET cannot exceed local P, which is not true in groundwater discharge zones in dry climates; this reduced groundwater loss to ET, or over-estimated groundwater recharge, leading to biased-high water table in arid basins. Second, vegetation uptake below 2m soil, and uptake of groundwater from the capillary rise, are not accounted for, further reducing groundwater loss, over-estimating recharge, and yielding biased-high water table. Third, by using long-term mean annual rech...

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    Competing Interests: None declared.

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