Research ArticleENVIRONMENTAL SCIENCE

Nonrainfall water origins and formation mechanisms

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Science Advances  22 Mar 2017:
Vol. 3, no. 3, e1603131
DOI: 10.1126/sciadv.1603131
  • Fig. 1 Extent of the Namib Desert and location of the study site.

    The map shows the location of the Gobabeb Research and Training Centre and the extent of the Namib Desert, as well as an inset showing the general landscape characteristics around the study area: the Kuiseb River and the gravel plains. CREDIT: K.F.K./Indiana University–Purdue University Indianapolis.

  • Fig. 2 Origins of fog water.

    The isotopic distribution of fog samples collected from the Gobabeb Research and Training Centre in relation to the GMWL and the LMWL, river water, and groundwater during the observation period (2014–2015). Fog regression lines indicate the source and classification of the fog. VSMOW, Vienna standard mean ocean water.

  • Fig. 3 Origins of dew water.

    (A) Groundwater-derived dew and fog lines indicating similar origins and plotting along the same evaporation line. (B) The LMWL at the Gobabeb Research and Training Centre with groundwater, Kuiseb River water, rain, and dew isotopes collected from 2014 to 2015. The GMWL was included as a reference.

  • Fig. 4 Differentiation of fog and dew.

    δ′17O versus δ′18O plots for bulk fog and dew samples showing that fog and dew are controlled by different fractionation processes: equilibrium and kinetic, respectively.

  • Table 1 Isotopic characteristics (mean ± SD) of the various water samples at the Gobabeb Research and Training Centre, Central Namib Desert.

    Nonrainfall water refers to combined fog and dew samples. ‰, per mil; n, sample size.

    Sample typeδ18O‰δ2H‰δ17O‰n
    Rain+2.16 ± 3.0+12.72 ± 28.84+0.83 ± 2.95
    Nonrainfall water+0.39 ± 3.5+3.74 ± 17.8+0.11 ± 1.953
    Dew (composite)−1.25 ± 3.1−7.97 ±13.7−1.22 ± 1.615
    Fog (composite)+1.03 ± 3.4+8.37 ± 17.3+0.64 ± 1.838
    River water (Kuiseb)−11.49−85.11−6.511
    Groundwater*−9.33 ± 0.3−63.97 ± 2.0−4.54 ± 0.24
    Groundwater−6.80 ± 0.2−45.88 ± 0.7−3.43 ± 0.22

    *Shallow aquifer.

    †Deep aquifer.

    • Table 2 Classification and isotopic characteristics (mean ± SD) of fog collected from the Gobabeb Research and Training Centre in the Namib Desert (2014–2015).

      n, sample size.

      Classificationδ18O‰δ2H‰δ17O‰dn
      Advective−0.74 ± 0.6+1.76 ± 5.1−0.20 ± 0.5+7.67 ± 1.315
      Mixed−0.43 ± 0.6+0.01 ± 5.3−0.23 ± 0.5+3.42 ± 1.010
      Radiation+1.41 ± 2.1+8.18 ± 13.3+0.78 ± 1.1−2.24 ± 3.48
    • Table 3 Isotopic characteristics (mean ± SD) and classification of dew samples from the Gobabeb Research and Training Centre in the Namib Desert (2014–2015).

      n, is sample size.

      Dew classificationδ18O‰δ2H‰δ17O‰dn
      Advective−2.01 ± 3.5−0.07 ± 13.5−1.77 ± 1.716.0±14.33
      Groundwater-derived−2.35 ± 2.7−10.12 ± 11.9−1.75 ± 1.48.67±9.76

    Supplementary Materials

    • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/3/e1603131/DC1

      note S1. Site description.

      note S2. Supplementary methods.

      note S3. Wind direction and speed measurements.

      table S1. Isotopic composition and d-excess of individual precipitation events captured during 2014–2015.

      table S2. Isotopic composition and classification of individual fog, dew, groundwater, and river samples captured between 2014 and 2015.

      table S3. Monthly rainfall that could have influenced fog and dew formation at the Gobabeb Research and Training Centre during the observation period.

      fig. S1. Hybrid Single-Particle Lagrangian Integrated Trajectory model (60) of 48-hour backward trajectory analysis of the five precipitation events captured at the Gobabeb Research and Training Centre during the observation period.

      References (6166)

    • Supplementary Materials

      This PDF file includes:

      • note S1. Site description.
      • note S2. Supplementary methods.
      • note S3. Wind direction and speed measurements.
      • table S1. Isotopic composition and d-excess of individual precipitation events captured during 2014–2015.
      • table S2. Isotopic composition and classification of individual fog, dew, groundwater, and river samples captured between 2014 and 2015.
      • table S3. Monthly rainfall that could have influenced fog and dew formation at the Gobabeb Research and Training Centre during the observation period.
      • fig. S1. Hybrid Single-Particle Lagrangian Integrated Trajectory model (60) of 48-hour backward trajectory analysis of the five precipitation events captured at the Gobabeb Research and Training Centre during the observation period.
      • References (61–66)

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