This study aims to understand the influence of vegetation cover on the hydrological response of the Hana forest watershed. Using the GR2M hydrological model, hydroclimatic data over the 2000-2018 period were simulated to obtain real evapotranspiration (ETR), infiltration (I), and runoff (R). These different water balance terms were then correlated with a time series of NDVI extracted from MODIS-Terra (MOD13Q1) images over the period 2000-2018. The calibration of the hydrological model over the periods 1984-1989 and 2000-2018, respectively gave good Nash values of 74.1% and 64.6%. The validation, on the whole, gives satisfactory Nash values, except for the 1990-1999 one which is 56.4%. Cusum and t-student tests confirmed a significant break at α=5% in 2009 in the NDVI time series. Statistical analysis around this break date reveals a good correlation between NDVI and rainfall on the one hand and between NDVI and real evapotranspiration on the other hand, with respective correlation coefficients of 0.68, 0.66 for the sub-period 2000-2009. The relationship between NDVI and runoff is relatively weak there with a value of 0.38. Very high correlation coefficient values were obtained over the period 2010-2018 between NDVI and rainfall (0.78), between NDVI and real evapotranspiration (0.72) and between NDVI and runoff (0.68). However, low correlation coefficients of the order of 0.53 and - 0.07 were recorded between the NDVI and infiltration respectively before and after 2009.

The Aghien lagoon watershed is located in peripheral north-east areas of Abidjan. This space is accelerated population growth more than more important. The rate of urbanization is higher than 60% in 2014 (RGPH, 2014). Also, does the acceleration of urbanization result in vegetation cover degradation for the benefit of the built environment and a peri-urban agriculture. Also, does the acceleration of urbanization result in vegetation cover degradation for the benefit of the built environment and a peri-urban agriculture. This study aims to analyze in part one the diachronic evolution of vegetation cover between 1987-2000 and 2000-2015, and second part its takes stock of this dynamic between 1987 and 2015. Thus, the analysis of land use dynamics in the Aghien basin is based on the the vegetation mapping of landsat images. The methodology is based on the supervised classification by maximum likelihood of landsat images The results of the dynamics of land use in the basin in 1987, 2000 and 2015 indicate a decline in forest cover and perennial crops in favor of built environment and bare soil (+10.98%), subsistence crops and fallow (+11.37) over the period (1987-2015). Urbanization and increase crops are caused modifications of vegetation cover in outskirt of basin. These changes are mainly due to demographic pressure and unsustainable agricultural practics.