Présentations Colloques

    Oral Presentation
    Session 7.05: The Challenges for Transboundary aquifer management
    Jean Margat - Aurélien Dumont
    Groudwater and surface water withdrawals during the XXth century - a global comparaison of thier evolution
    In a context of a lack of historic data and statistics on global groundwater withdrawals, this work aims to present an overview of the global trend of groundwater withdrawals during the XXth century. Based on the observation that around 80% of current withdrawals, which amount to nearly 1,000 km3 yr, are located in a few countries (around 10), with the first three countries – India, China, and the U.S. – comprising half of the global value (Margat & Van der Gun, 2013), the approach consists in retracing the history of the withdrawals in these countries, to deduce the probable trend in the worldwide groundwater withdrawals on the second part of the XXth century. This has been possible with some interpolations for the period 1950 to 2000. ****Comparing these results with the trend for total water withdrawals in the XXth century, a main conclusion is that the growth of the global groundwater withdrawals may have been much steeper than the growth of the surface water withdrawals in the last decades, with groundwater withdrawals multiplied by ten between 1950 and 2010. The share of groundwater withdrawals has also notably raised- from less than 5 % in 1950 to 25 % in 2010.This observation may be explained by the increase in individual users (mainly farmers), who directly pump groundwater, mainly for irrigation. There are now millions of them. As a comparison, use of surface water has been, and still is, mainly realized by (public or private) collective actors. ****In addition to the discussion of the different steps for this overview and the reasons and main implications of the rise in global groundwater use, the presentation will highlight the challenges and the limits of this global approach while promoting a better and more systematic knowledge on groundwater withdrawals.**


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