One of today's key research challenges is now to provide and anticipate climatic changes so that we can respond and adapt to these future developments. Global reheating of the earth and weather forecasts are a growing risk of climatic changes that are not without consequences on the ecosystems whose the watershed of Oueme. The objective of this study is to analyze the availability of water resources with the climatic variability in the lower Oueme valley in south of Benin. The data and methods used are rainfall, ETP, planimetric data, land use extracted from Landsat 8 OLI / TIRS 2016, ArcGIS 10.1 software for mapping, Khronostat 1.01 for detection of ruptures and field observations, etc. This information after treatment helped to determine the physiognomy of the climate in the lower Oueme valley. The results obtained show an unequal distribution of rainfall marked by the continuous changes of the natural conditions of the basin. The study identifies three phases in the evolution of rainfall. The first 1987-1990 is marked by rainfall surpluses. The second is characterized by rainfall deficits between the period 1990-2006 and the last one characterized by a very strong instability in the evolution of the rainfall, concerns the period 2006-2016. The application of Pettitt test to this chronologic series revealed a break in stationarity at the 95% threshold, thus highlighting two sub-periods, 1987-2006 and 2007 -2016. This rainfall decrease anchor decrease of superficial flow between 0,2% and 1% in the lower Oueme valley.

The capitalization of the farming techniques for food security in Benin has been studied. The effects of climate change and the rainfall changeablenesses have modified not only the dates of seedling but also the abandonment of some speculations. In order to ensure their food security, the populations have revisioned their farming techniques. The climate data which were used for this work are obtained with the ASECNA and those socio-economic were collected near 300 producers. As a matter of fact, in the north 40% of the yielded speculations today can be considered as introduced twenty years ago. In this area in the years 60s there are crops such as yam, voandzou, maize, peanuts, and garden pea. The current crops are yam, maize, and sorghum. Crops such as peanuts, voandzou are more and more withdrawn from the speculation ranges. Furthermore, the situation in the centre of Benin is enough animated. In effect, about 65% yielded speculations in the past were abandoned at the profit of new estimated ones more adapted to the current climatic conditions. To ensure their food security, the populations have spared the speculations such as maize, yam, and peanut. Crops such as sorghum, millet, voandzou and garden peas are almost given up and replaced by soya which represents now the speculation that occupies 45% of the farmed surfaces. In the south of the country, about 30% only of the farming techniques have undergone changes. The climatic changeableness has provoked for instance the introduction of cotton crop which in the past was quasi impossible.

The present study related to the agro-ecological analysis of the area catchment Okoriko in the district of Toui at Ouèssè (department of the hills). The degradation of the resources through the operating systems is at the origin of the analysis agro-ecological to understand the evolution of the catchment area. From this analysis, an inventory of the various agricultural activities undertaken by the population of the catchment area was made, an evaluation of the impact of the agricultural activities on the environment is also made. The data processing collected on the ground, made it possible to note that in the area catchment Okoriko, the principal operating systems are : agriculture, fishing, the breeding, and forestry exploitation. Agriculture and the forestry exploitation are the most practised activities and occupy more half of the population. Indeed, more than 67 % of the ecosystems are occupied by agricole lands and nearly 10 % of the population have their activity directed towards the forestry exploitation. Only 21 % of the households undertake activities like the breeding, and fishes it. These activities are factors of pollution water, ground, vegetation, watery fauna.