West African basins play a vital role in the socio-economic development of the region. They are mostly trans-boundary and sources of different land use practices. This work attempts to assess the spatio-temporal land use and land cover changes over three South Western African basins (Volta, Mono and Sassandra basins) and their influence on discharge. The land use and land cover maps of each basin were developed for 1988, 2002 and 2016. The results show that all the studied basins present an increase in water bodies, built-up, agricultural land and a decline in vegetative areas. These increases in water bodies and land use are as a result of an increase in small reservoirs, of dugouts and of dam constructions. However, the decline in some vegetative clusters could be attributed to the demographic and socio-economic growth as expressed by the expansion of agriculture and urbanization. The basic statistical analysis of precipitation and discharge data reveals that the mean annual discharge varies much more than the total annual precipitation at the three basins. For instance, in the entire Volta basin, the annual precipitation coefficient of variation (CV) is 10% while the annual discharge CV of Nawuni, Saboba and Bui are 43.6%, 36.51% and 47.43%, respectively. In Mono basin, the annual precipitation CV is 11.5% while the Nangbeto and Athieme annual discharge CV are 37.15% and 46.60%, respectively. The annual precipitation CV in Sassandra basin is 7.64% while the annual discharge CV of Soubre and Dakpadou are 29.41% and 37%, respectively. The discharge varies at least three times much more than the precipitation in the studied basins. The same conclusion was found for all months except the driest months (December and January). We showed that this great variation in discharge is mainly due to land use and land cover changes. Beside the hydrological modification of the land use and land cover changes, the climate of the region as well as the water quality and availability and the hydropower generation may be impacted by these changes in land surfaces conditions. Therefore, these impacts should be further assessed to implement appropriate climate services and measures for a sustainable land use and water management.

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Depuis sa création, le Parc national du Mont Péko est sujet à diverses pressions anthropiques. Ces pressions ont été accentuées durant les conflits armés en Côte d’Ivoire entre 2002 et 2011. L’intensification des pressions aurait entraîné une augmentation du taux de déforestation dans le parc. Pour vérifier cette hypothèse, la présente étude visait à déterminer l’effet des conflits sur la dynamique forestière du parc. À cet effet, quatre images satellitaires Landsat ont été analysées pour examiner les changements d’occupation des sols avant, pendant et après les conflits. Les résultats de ces travaux révèlent une forte réduction des surfaces forestières durant les conflits, qui s'est accentuée pendant la période post-conflit. En effet, 5,65 % de pertes se sont produites avant les conflits à un taux annuel de 0,42 %, contre 28,03 % pendant les conflits à un taux annuel de 3,92 %, et 34,02 % après les conflits à un taux annuel de 14,41 %. Cette aggravation de la déforestation dans le parc est liée à la culture illégale du cacao. L’infiltration massive des populations paysannes dans cette aire protégée pendant les conflits a entraîné une exacerbation des pressions. Une surveillance constante et un aménagement des zones converties en plantation de cacao afin d’accélérer la régénération dans le parc s’avèrent donc nécessaires. En outre, les résultats soulignent la vulnérabilité des aires protégées lors des conflits et l’urgence de la prise de mesures de sécurisation de celles-ci pour prévenir les risques de dégradation.

The management of water resources in watersheds has become increasingly difficult in recent years due to the frequency and intensity of drought sequences. The Lobo River catchment, like most tropical regions, has experienced alternating wet and dry periods. These drought periods have a significant impact on the availability of water resources in the basin. The objective of this study is to analyse the impact of meteorological drought on flows in the Lobo River catchment. Therefore, using the Normalized Precipitation and Evapotranspiration Index (SPEI) and the Drought Flow Index (SDI), the characteristics of droughts were studied. The results of this study show that meteorological droughts were more frequent than hydrological droughts in the Lobo River watershed. However, the hydrological drought was longer and more intense than the meteorological drought. The greater relationship between meteorological and hydrological drought was observed at the Daloa and Vavoua station (0.43 < r < 0.50) compared to the Zuenoula station (r < 0.5). In addition, there was a resumption of precipitation and runoff between 2007 and 2013 in the basin. The study of these climatic trends would be very useful in the choice of management and adaptation policies for water resources management.

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

From medium-resolution satellite images (Landsat TM, ETM+ and OLI), the spatial dynamics of land cover and land use are highlighted. The objective of this study is to quantify the evolution of land use in the watershed of the Lobo River upstream of Nibéhibé between 1986 and 2019 in order to analyze the impacts of human activities on the landscape. The study method was based, on the one hand, on the processing of satellite images, for the analysis of the dynamics of land use and, on the other hand, on the CA-Markov model, for the prediction of land use by 2050. It emerged from this study that the land use maps produced made it possible to highlight the spatio-temporal dynamics of land use on the basin. For the period from 1986 to 2019, there is a decrease in the area of forests in favor of built-bare ground and crops and fallows. A land use scenario for the years 2019 and 2050 was simulated with an accuracy of 87.11%. The regressive trend in forests seems to continue in the future with current land use practices.

Management of hydroelectric dams is an aspect of sustainability that comes with resolving problems locally. The use of global indicators has not been a sustainable solution, thus the need for local indicators. Besides, current sustainability assessment tools lack the integration of climate, making assessments in a climate change context impossible. In this paper, we present management and sustainability assessment in a climate change context using sustainability indicators. We modeled a change in the climate using normal, moderate, and extreme climate conditions defined by Standardized Precipitation Indices (SPI) values. Out of 36 years analyzed, 24 years fall in the near-normal climate regime, and the remaining 12 years in moderate and extreme conditions, making near-normal climate regime the basis for managing the Taabo Dam. The impact of climate, techno-economic, and socio-environmental indicators on sustainability were investigated, and the results were analyzed according to scenarios. Climate adaptation shows higher sustainability indices than techno-economic and socio-environmental scenarios. Probability matrices show high and low values, respectively, for environmental and flooding indicators. Risk matrices, on the other hand, show that even with small probability values, risks still exist, and such small probabilities should not be taken as an absence of risk. The study reveals that sustainability can be improved by integrating climate into existing assessment methods.

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