Instability of space-time rainfall regimes in the payment of basin Mono-Couffo and its impact on the flow of 1961 to 2000.

The catchment area of Mono-Couffo complex, is located in the Gulf of Benin, in the southern part of the Republics of Benin and Togo, at the continent-ocean interface. It lies about 526 km from north to south between 06 ° 16 'and 09 ° 20'N and covers an area of 27 870 km ². The analysis of the variation in rainfall totals for the period 1961-2000 in the basin of Mono-Couffo, between Benin and Togo has been a slight decrease in precipitation. This study aims to identify possible changes in the precipitation regime of the basin and their potential impact in the hydrological functioning of river Couffo. The data used are the monthly precipitation of a network of 25 stations within the basin and vicinity from the database of ASECNA Benin and the National Weather Togo and flow of the river Couffo to Lanta. To establish a typology of seasonal patterns, a matrix composed of 1025 sets of monthly precipitation (January to December) is lodged. It comprises 40 years of observations for each of 25 stations in the study area, or 1000 "actual" in total. Add to this the ways regimes (1961-2000) calculated by each station, or 25 series. The types of schemes combined resources and real uses a bottom-up hierarchical classification applied to the matrix of 1025 sets of 12 observations. Thus, a hierarchical ascending classification combined forty years of data and each of the twenty five stations can be identified four main types of schemes and real means. The distinction between the regimes of monsoon rain oceanic and continental hydrosystem on Mono-Couffo, shows that the distribution of rainfall varies from one medium to another and from one year to another. However, this variation is much more marked in the center of the basin where it moves from the bimodal to unimodal regime away from the coast and north of the basin where a single predominant type of plan