Climate change and anthropization are major drivers of river flows variability. However, understanding their simultaneous impact on discharges is limited. As a contribution to address this limitation, the objective of this study is to assess the impact of climate change and anthropization on the discharges of two watersheds of Central Africa (Nyong and Ntem) over a recent period. For this, the hydropluviometric data of the watersheds concerned were analyzed using the Pettitt test. Similarly, the dynamics of the main land use modes (LUM) have been assessed, through classifications obtained from the processing of Landsat satellite images of the watersheds studied on two dates. The results of this study show that in Central Africa, annual discharges have decreased significantly since the 1970s, and yet the decline in annual rainfall does not become significant until the 2000s. The discharges of the rainy seasons (spring and autumn) recorded the most important changes, following variations in the rainfall patterns of the dry seasons (winter and summer) that precede them. Winters experienced a significant decrease in precipitation between the 1970s and 1990s, which caused a drop in spring flows. Their rise, which began in the 2000s, is also accompanied by an increase in spring flows, which nevertheless seems rather slight in the case of the Nyong. Conversely, between the 1970s and 1990s, there was a joint increase in summer rainfall and autumn flows. A decrease of summer rainfall was noted since the 2000s, and is also noticeable in autumn flows. Maximum flows have remained constant on the Nyong despite the slight drop in rainfall. This seems to be the consequence of changes in land use patterns (diminution of forest and increasing of impervious areas). The decrease in maximums flows noted on the Ntem could be linked to the slight drop in precipitation during the rainy seasons that generates it. Factors such as the general decrease in precipitation during the winter and the reduction in the area occupied by water bodies could justify the decrease in minimum flows observed in the two watersheds. These findings would be vital to enhance water management capabilities in the watersheds concerned and in the region. They can also give some new elements to study and understand the seasonal variation and fresh water availability in downstream, estuaries and coastal areas of the regional rivers.

Due to climate and environmental changes, sub-Saharan Africa (SSA) has experienced several drought and flood events in recent decades with serious consequences on the economy of the sub-region. In this context, the region needs to enhance its capacity in water resources management, based on both good knowledge of contemporary variations in river flows and reliable forecasts. The objective of this article was to study the evolution of current and future (near (2022–2060) and distant (2061–2100)) flows in the So'o River Basin (SRB) in Cameroon. To achieve this, the Pettitt and modified Mann–Kendall tests were used to analyze hydrometeorological time series in the basin. The Soil and Water Assessment Tool (SWAT) model was used to simulate the future flows in the SRB. The results obtained show that for the current period, the flows of the So'o decrease due to the decrease in precipitation. For future periods, a change in precipitation in line with the predictions of the CCCma model will lead to a decrease in river discharge in the basin, except under the RCP8.5 scenario during the second period (2061–2100), where will note an increase compared to the historical period of approximately +4%. Results from the RCA4 model project an increase in precipitation which will lead to an increase in river discharge by more than +50%, regardless of the period and the scenario considered. An increase in discharges was noted in some cases despite a drop in rainfall, particularly in the case of discharges simulated for the second period (2061–2100) from the outputs of the CCCma model. This seems to be a consequence of the increase in impervious spaces, all the more the runoff increases during this period according to the model. Results from this study could be used to enhance water resources management in the basin investigated and the region.

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Le changement climatique et l’anthropisation sont les principaux forçages qui influencent significativement la variabilité des écoulements des cours d’eau. Cependant, la compréhension de leur impact simultané sur les écoulements reste limitée. L’objectif de cette étude est d’appréhender l’impact de la variabilité des précipitations et de l’anthropisation sur les écoulements du bassin versant de la Mefou sur une période récente (1950-51 à 2018-2019). Pour cela, les données hydropluviométriques du bassin concerné ont été analysées au moyen du test de Pettitt. De même, la dynamique des principaux MOS (modes d’occupation du sol) a pu être appréciée, et ce au moyen des classifications supervisées effectuées à partir du traitement des images satellitaires Landsat du bassin étudié à deux dates. Les résultats de cette étude montrent que les débits moyens (+27,8% à +66,4%) et extrêmes (31,2% à 82,3%) de ce bassin augmentent depuis 1985-86, contrairement à la pluviométrie, qui elle diminue d’une façon générale pour toutes les saisons à compter de la décennie 1970, en dehors de l’été (+42,8%), où l’inverse est observé. Les changements d’occupation du sol (augmentation des espaces imperméabilisés et diminutions de la forêt et des plans d’eau) semblent être la cause principale de la hausse des écoulements relevée. Les évolutions pluviométriques observées dans ce bassin ont juste contribué à amplifier la variabilité des écoulements durant la période étudiée. L’été et le printemps pour lesquels les pluies ont respectivement enregistré une rupture à la hausse et une absence de rupture sont également les saisons pour lesquelles les augmentations des écoulements sont les plus importantes. A l’inverse, l’automne et l’hiver qui ont enregistré des diminutions significatives des pluies ont connu les augmentations les moins importantes. Ces résultats pourraient être utiles pour la planification à long terme de la demande et de l'utilisation de l'eau dans ce bassin, ainsi qu'à l’amélioration des simulations futures du débit du collecteur principal et la prévention des catastrophes socio-environnementales comme les inondations.     The objective of this study is to understand the impact of rainfall variability and anthropization on the flows of the Mefou watershed over a recent period. For this, the hydropluviometric data of the catchment concerned were analyzed using the Pettitt test. Likewise, the dynamics of the main land-use patterns could be assessed, using supervised classifications carried out from the processing of Landsat satellite images of the basin studied at two dates. The results of this study show that the average and extreme flows of this basin have been increased since 1985-86, unlike the rainfall, which generally decreases for all seasons from the 1970s, apart from the summer, where the reverse is observed. Land-use changes (increase in impervious areas and a decrease in forest and water bodies) seem to be the main cause of the observed increase in runoff. The rainfall changes observed in this basin have just contributed to amplifying this increase in runoff in some cases and attenuating it in others. The summer and the spring for which the rainfall recorded respectively an increasing break and no break are also the seasons for which the increases in runoff are the most important. Conversely, autumn and winter, which saw significant decreases in rainfall, experienced the smallest increases. These results could be useful for long-term planning of water demand and use in this basin, as well as for improving future simulations of main collector flow and preventing socio-environmental disasters like flooding.