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Long-term Hydrological Variations of the Ogooue River Basin
  • +11
  • Sakaros Bogning,
  • Frederic Frappart,
  • Gil Mahé,
  • Fernando Niño,
  • Adrien Paris,
  • Joelle Sihon,
  • Franck Ghomsi,
  • Fabien Blarel,
  • Jean-Pierre Bricquet,
  • Raphael Onguene,
  • Jacques Etame,
  • Frederique Seyler,
  • Marie-Claire Paiz,
  • Jean-Jacques Braun
Sakaros Bogning
Department of Earth Sciences, University of Douala, Cameroon

Corresponding Author:[email protected]

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Frederic Frappart
LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS OMP, Toulouse, France.
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Gil Mahé
HydroSciences Montpellier, Université de Montpellier, CNRS, IRD, Montpellier, France.
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Fernando Niño
LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS OMP, Toulouse, France.
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Adrien Paris
Collecte Localisation Satellite (CLS), 11, Ramonville-Saint-Agne, France.
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Joelle Sihon
GET, Université de Toulouse, CNES, CNRS, IRD, UPS OMP, Toulouse, France.
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Franck Ghomsi
Department of Physics, The University of Yaoundé 1, Yaoundé, Cameroun.
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Fabien Blarel
LEGOS, Université de Toulouse, CNES, CNRS, IRD, UPS OMP, Toulouse, France.
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Jean-Pierre Bricquet
HydroSciences Montpellier, Université de Montpellier, CNRS, IRD, Montpellier, France
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Raphael Onguene
JEAI-RELIFORME, The University of Douala, Douala, Cameroon
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Jacques Etame
Department of Earth Sciences, The University of Douala, Douala, Cameroon.
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Frederique Seyler
SPACE-DEV, Université de Montpellier, IRD, Université des Antilles, Université de Guyane, Université de La Réunion, Maison de la Télédétection, Montpellier, France
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Marie-Claire Paiz
The Nature Conservancy Gabon Program Office, Libreville, Gabon
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Jean-Jacques Braun
LMI-DYCOFAC, IRD-Cameroon, Yaoundé, Cameroon
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Abstract

This chapter describes the variability of rainfall and river discharges in the Ogooué River basin (ORB) in recent decades (since 1940). Due to its location crossing the Equator, the ORB receives abundant precipitation that maintains one of the world’s best-preserved ecosystems. In contrast to neighboring forest basins that have been severely degraded because of deforestation, mining resources extraction, extensions of agricultural areas, and river transport, which is a crucial alternative to the cruel lack of road infrastructures, the ORB is experimenting with an exceptional conservation policy in the region. For example, the rural penetration rate in Gabon is about 1 inhabitant per km² and many studies report a deforestation rate close to 0%, with even full natural regeneration. However, the fluctuations of the standardized anomaly index of rainfall in the ORB show three main phases of variations: the first wet phase was characterized by abundant precipitations from 1940 to 1970, the second phase of the long-term mild drought was extended in the 1970s and 1980s and the final third phase presented a slight return of abundance in precipitation. Even though drought severity in the ORB was mainly weak, its effects in river discharges were very sensitive on seasonal and inter-annual scales. The pure equatorial regime of the ORB characterized by equal maximum floods in spring and autumn changed significantly from the difference between both maximum discharges of 13.5 % during the 1960s to 27.0 %, 38.4 %, 33.9 %, and 26.7 % for the 1970s, 1980s, 2000s and 2010s respectively. A brief comparison between the ORB and the Congo River basin showed that changes in the ORB are part of a regional process that Central Africa is undergoing with some spatial heterogeneities.
25 Feb 2022Published in Congo Basin Hydrology, Climate, and Biogeochemistry on pages 367-389. 10.1002/9781119657002.ch19