Contribution of GR6J model to the assessment of the water balance in the Aghien lagoon basin in southern Côte d'Ivoire

AGHIEN lagoon, a freshwater on the periphery of Abidjan city, was selected under the Renovated Partnership for Research at the Development Department of Côte d'Ivoire (PReSeD-CI), to overcome a serious problem of drinking water needs, which the megalopolis has been facing for nearly two decades. For a better understanding of the functioning of this lagoon, we set ourselves the general objective of evaluating the resource. More specifically in this article, the aim was to assess the water balance in the BETE sub-basin, the main tributary of the lagoon with a hydrological model. To achieve this, an extensive hydroclimatic data measurement network has been deployed on the lagoon watershed since 2015. The modeling was carried out using the daily data for the period 2015-2017 under the model GR6J (Rural Engineering at 6 parameters at the time step Daily). The calibration and validation of it gave satisfactory values of Nash respectively of 75% and 74%. The characterization of the main components of the water cycle over the period 2016-2017 for an average annual rainfall of 2472 mm, has given: a proportion of the flow equivalent to 50%; that of evapotranspiration is evaluated at 40% while infiltration represents 10%. These preliminary results made it possible to understand that nearly half of the precipitation of the BETE basin would flow towards the Aghien lagoon