Science et changements planétaires / Sécheresse


The hydrology of the Charente river: between nature and anthropization (1960-1994) Volume 13, issue 2, Juin 2002


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EA 22 52 - ICOTEM (Identité et connaissance des territoires et des environnements en mutation) Maison des sciences de l'homme et de la société, 99, avenue du Recteur-Pineau, 86022 Poitiers.
  • Page(s) : 105-12
  • Published in: 2002

With a pluvio-oceanic regime, the Charente river reflects the pluviometrical pulsations of the oceanized climate prevailing in the West-Center of France. Over a century, its pluviometry underwent a five-year cyclical regime, coupled with a decennial cyclical regime. However, between the end of the 19th century and the end of the 20th century, there is a tendency to a linear growth in the annual rainfall. This remark would be totally meaningless if the flow, after transmitting the same cyclical pulsations, was not, on the contrary, characterized by a general tendency to a decline of the discharge. The hydrologic behaviour of the Charente river between 1960 and 1994 is a perfect illustration of this. From the monotonous curve of the classified daily rate of flow, some "characteristic flows" of high and low waters have been defined. The frequency of their annual occurrence is in perfect conformity with the rhythm of the decennial pulsations : this expresses the sensitivity of a watershed sensitive to pluviometrical fluctuations and lacking in groundwaters. However, while the frequency of high waters shows an alternancy in keeping with the pluviometrical fluctuations, the frequency of low waters has been growing in an irrational manner since 1976. After suggesting a structural climatic cause - global change - the statistical analysis tends to point out to an origin linked with specific conditions - some excessive agricultural pumping -- an explanation which seems te be confirmed by the analysis of the evolution of the cultivation of Indian Corn and oleaginous plants.