Impacts socio-économiques et environnementaux des risques d’inondation dans le bassin versant de l’Oti au Togo (Afrique de l’Ouest)

The Oti River watershed, in Togo, is currently confronted with climate variability phenomena characterised by recurrent flooding events that weaken human and environmental systems. The objective of this study is to analyse the socio-economic and environmental impacts of floods in the Oti watershed in Togo. To this end, rainfall data (daily rainfall from 1961-2017), hydrometric data (daily flows from 1961-2017) and epidemiological data from the Mango health district were used. Similarly, agricultural statistics and socio-economic survey data were used. Rainfall and flow anomaly indices and McKee's (1993) classification were used to characterise flood hazard thresholds. Field surveys were carried out among the population to find out the impacts caused by floods in the watershed. The results show that 1962, 1964 and 2015 were extremely wet years and 1968, 1999, 2012 and 2013 are very wet years in the whole Oti watershed. The hydrometric indices show a significant variation in annual maximum flows from the 1960s onwards in the Oti sub-watershed of Mango and Mandouri. This means that the evolution in the series of maximum flows is linked to the extreme daily rainfall. The risk of flooding in the watershed has socio-economic, health and environmental impacts. These impacts can be summarised as loss of human life, precious objects and income of economic actors, increase in cases of diarrhoeal diseases and malaria, psychological scars of victims, soil erosion, loss of plant and animal biodiversity, water and nature pollution, etc

Application d’un modèle conceptuel à l’analyse de la dynamique hydrométéorologique des crues dans un bassin-versant en milieu tropical humide : cas du fleuve Mono.

7 pagesInternational audienc

Farmers’ Knowledge and Management Practices of Fall Armyworm, Spodoptera frugiperda (J.E. Smith) in Benin, West Africa

Spodoptera frugiperda has caused significant losses of farmer income in sub-Saharan countries since 2016. This study assessed farmers’ knowledge of S. frugiperda, their perceptions and management practices in Benin. Data were collected through a national survey of 1237 maize farmers. Ninety-one point eight percent of farmers recognized S. frugiperda damage, 78.9% of them were able to identify its larvae, and 93.9% of the maize fields were infested. According to farmers, the perceived yield losses amounted to 797.2 kg/ha of maize, representing 49% of the average maize yield commonly obtained by farmers. Chi-square tests revealed that the severity of the pest attacks was significantly associated with cropping practices and types of grown maize varieties. About 16% of farmers identified francolin (Francolinus bicalcaratus), village weaver (Ploceus cucullatus), and common wasp (Vespula vulgaris) as natural enemies and 5% of them identified yellow nutsedge, chan, shea tree, neem, tamarind, and soybean as repellent plants of S. frugiperda. Most farmers (91.4%) used synthetic pesticides and 1.9% of them used botanical pesticides, which they found more effective than synthetic pesticides. Significant relationships exist between farmers’ management practices, their knowledge, organization membership, and contact with research and extension services. More research is required to further understand the effectiveness of botanical pesticides made by farmers against S. frugiperda and to refine them for scaling-up

Climate and extreme rainfall events in the Mono river basin (West Africa): investigating future changes with Regional Climate Models.

27 pagesInternational audienceThis study characterizes the future changes in extreme rainfall and air temperature in the Mono river basin where the main economic activity is weather dependent and local populations are highly vulnerable to natural hazards, including flood inundations. Daily precipitation and temperature from observational datasets and Regional Climate Models (RCMs) output from REMO, RegCM, HadRM3, and RCA were used to analyze climatic variations in space and time, and fit a GEV model to investigate the extreme rainfalls and their return periods. The results indicate that the realism of the simulated climate in this domain is mainly controlled by the choice of the RCMs. These RCMs projected a 1 to 1.5 °C temperature increase by 2050 while the projected trends for cumulated precipitation are null or very moderate and diverge among models. Contrasting results were obtained for the intense rainfall events, with RegCM and HadRM3 pointing to a significant increase in the intensity of extreme rainfall events. The GEV model is well suited for the prediction of heavy rainfall events although there are uncertainties beyond the 90th percentile. The annual maxima of daily precipitation will also increase by 2050 and could be of benefit to the ecosystem services and socioeconomic activities in the Mono river basin but could also be a threat