No abstract

Sustainable management of Ivory Coast's freshwater reserve at a catchment scale is an essential way in the policies of land use sustainable management. Thus, the implementation of physical conceptual semi-distributed SWAT model required a good knowledge of the watershed and a large number of physic-chemical data available that have been prior adapted to Ivory Coast's climatic and soil conditions. The whole simulation span was divided into calibration set (1982)(1983)(1984)(1985)(1986) and validation set (1987)(1988)(1989)(1990). The SUFI-2 algorithm was used for parameters optimization. The sensitivity analysis focused on 8 parameters related to runoff, soil, evaporation, main channel and groundwater. The performance criteria were based on the P-factor, R-factor and the two objective functions which are Nash-Sutcliffe coefficient and the coefficient of determination. Although Taabo river basin like African basins suffers from a significant lack of data, the objective functions showed the robustness of the model to climate variability. The calibration launched during a wet period gave objective functions higher than 0.7 while validation performed in less humid period gave performance criteria around 0.6. During the simulation period, Taabo river basin daily green water ranged from 0.044 to 50.257 mm/day with a total average of 3,090.9 mm per year. As for blue water, it is ranged from 0.032 to 0.552 mm/day with an annual total average of 29.19 mm.

Floods result from the overflow of water which submerges the surrounding land. They are frequent on the coast of Côte d'Ivoire during the rainy season and have more or less serious consequences on the populations, property and the environment. The study site is the San Pedro river basin. It is a coastal catchment area characterized by an average annual rainfall of up to 2000 mm and subject to recurrent flooding. The objective of this study is to assess the risk of flooding during the great rainy season of 2017. The study aims to study flood hazard, assess vulnerability and map flood risk areas. The methodological approach is based on the use of C-band (5.6 cm) radar remote sensing Kouassi et al.; AJGR, 3(2): 1-8, 2020; Article no.AJGR.55959 2 data acquired by the Sentinel-1 sensor at 12-day intervals. These data are in GRD (Ground Range Detected) level 1 format and were used to calculate the radar backscatter coefficient. The results obtained allowed to map the extent of the flooded areas and showed that more than 6,000 ha of land is flooded for more than 3 days. Sentinel-1 has enormous potential to identify flooding risky areas and to continuously monitor them. Original Research Article

This study aims to analyze the input data of the semi-distributed SWAT model that can be used as a hydrological study of the Lobo water reservoir. The adopted approach includes two major steps: The input data estimation and the watershed configuration. The estimation of input data consists in the collection and calculation of input data necessary for the watershed configuration. The input data collected and estimated were a digital elevation model (DEM), a soil map, soil physico-chemical parameters (grain size, K erodibility coefficient, exchangeable anions, soil density, organic carbon, soil electrical conductivity), a land cover map, information on agricultural practices and daily climate data (Temperature, Rainfall, Sunshine, Wind Speed ​​and Relative Humidity). The watershed configuration consisted of the extraction of watershed boundaries and watershed network, the integration of data, the calculation of hydrological response units (HRU) and the watershed configuration. The SWAT model permitted to extract a single type of soil for Lobo water reservoir watershed. The watershed has a dense drainage system which means that the area is heavily drained. The degraded forest occupies 37% of the watershed followed by agricultural land (30% of the territory). 213 HRU from 39 sub-watersheds were also obtained. These data are an indispensable tool for the hydrological simulation of the Lobo reservoir.

The lake system of Taabo watershed contributes at 35% in the country electrification. Besides this use, water is also used in agriculture, fishing and for drinking water. The increasing human activities in its basin led to siltation of Kossou's Lake and eutrophication of 26% of Taabo's Lake total area. However, no study has yet been performed to protect or prevent this resource against pollution. This study is the first in Ivory Coast intending to delineate three protection areas around the watershed lakes. It tries firstly to define all parameters involved in the surface water intrinsic vulnerability. Their integration in multicriteria analysis coupled to use of Geographic Information System (GIS) has then used to delineate protection area around the basin lakes. Three zones were proposed: (1) the immediate protection zone, with a radius of 2000 m around the lake including water, its islands and coastal strip; (2) the near protection perimeter, limited to intense vulnerability zones in the immediate sub-basins of lake; (3) the distance protection perimeter has been estimated to the whole catchment in order to take into account diffuse pollution. As conclusion of protection perimeters elaboration, assistance must be provided for restoring quality and quantity of basin water.