Nature 221, 461 - 462 (01 February 1969); doi:10.1038/221461a0

Variability in Specific Conductance and pH in the Casiquiare–Upper Orinoco

J. B. THORNES

Department of Geography, London School of Economics, London WC2.

RECENT work has contributed significantly to our knowledge of the quality and suspended sediment content of the rivers of the Amazon basin^1–3. Following the usual procedure, some authors extrapolate beyond the monthly, semi-annual or even sporadic samples to the discharge of sediments over extensive periods of time and over wide ranges of conditions. Tropical lowland rivers, especially in the wet season, are characterized by low concentrations of dissolved solids¹. By extrapolation, over whole river systems and for long periods of time, small differences in various stream characteristics become greatly magnified. In April and May 1968, samples were obtained from the Casiquiare and Upper Orinoco Rivers, with a view to determining the degree of variability in various river characteristics. This communication refers to variability in pH and specific conductance. Other results, currently being evaluated by Mr. A. C. Edwards, University of East Anglia, will be published as they become available. The field work was carried out during the Geographical Magazine Amazonas Expedition.

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