CLIMATE CHANGE AND THE AVAILABILITY OF WATER RESOURCES IN BENIN

It is likely that climate change in the coming decades, even very few, will produce more important impacts on thesocio-economic systems than in the past, due to the growth in world population and the increasing sophistication of technology and development issues (Issa, 1995). According to UNESCO (2006), climate change will be responsible for 20% of the worsening water scarcity in the world. This looming water crisis will be induced by changes in the parameters that determine the water cycle (Totin, 2005). The study is based on analysis of a baseline from which the main meteorological parameters (rainfall, flow, etc.) are projected to 2025 time horizon. It corresponds to the horizon of the prospective study for 2025 in Benin. From these basic parameters, the main elements to characterize water resources (such as infiltration, the volume of water available water bodies, etc.) were determined for each time horizon. Research carried out in different regions of the Benin on climate issues, surface and ground water (Gbatcho 1992; Boko, 1998; Boukari, 1998 Linsoussi, 2000; Sadji, 2004; Amoussou, 2003 and 2005; Totin, 2003 and 2005; Tossa, 2005; Vissin et al., 2006 ; Vissin, 2001 and 2007 ; Alassane and Boukari, 2007; Idiéti, 2009 ; Totin, 2009) attest ruptures occurred in hydro-climatic chronicles during the 1970s and indicate a downward trend in superficial water resource two to four folds greater than that of rainfall in key watersheds. Similarly, the aquifers record deficit on refill aquifers (Boukari, 1998; Totin, 2005) and a variation of hydro-chemical caracteristics (Alassane, 2004). If this climate and hydrological trend continues, hydrological drought will lead to a considerable reduction of water resources and a potential shortage. Similarly, the water quality will be affected in various ways. Very wet weather events would induce an increased transfer of pollutants to the water bodies as opposed to dryness that would accentuate deterioration especially of the bacteriological quality of water resources. Facing to the quantitative and qualitative degradation of both surface and groundwater should develop strategies to increase the potential availability of the resource. To this end, it is important above all to protect areas of groundwater recharge, stabilize stream banks and water bodies. Improving the quality of water resources in a changing climate context implies that people are aware of the risks of shortage and of agricultural good practices (no use of chemical fertilizers and synthetic pesticides), management of solid and liquid waste. The water law must be adapted to the context of climate change and vulnerability of the water resource

Peuplement Spontané Et Accès À L’éducation Primaire Dans La Commune De Bantè Au Centre Du Bénin

Achieving universal primary education is the second Millennium Development Goals that Benin missed in 2015 with a national rate of 74 percent. The reasons for this failure are varied with notable spatial specificities. The present research aims to contribute to the analysis of the specific causes of this failure in the Bantè Commune. The data used relate to the number of children enrolled in schools, the number of schools, and the number of settlements (villages, hamlets, and manned farms) on several dates in the Commune. In addition, information was collected from selected households in several localities. Individual interviews and groups as well as direct field observations were the collection techniques used. The tools and parameters of the descriptive statistics and the cartographic approach made it possible to process the data collected. The results show a disparity in the spatial distribution of primary schools compared to inhabited places. The result shows a geographical inaccessibility of schools for the children of many hamlets and farms. This situation is mainly inherent to a spontaneous settlement dynamics which characterizes the Commune. This concern, therefore, deserves consideration if access to primary education is a global challenge that is again relaunched by 2030. This is usually done within the framework of the Sustainable Development Goals

Traditional Adaptation Strategies to Hydrosystem Degradation for Sustainable Management of the Aheme Lake in Benin (West Africa)

The water system like the lake Aheme are abundant in halieutic species (fish, crabs, shrimps…) exploited by resident populations. Over exploitation and high degradation of ecosystems of the lake Aheme induce inexorably fish productivity reduction. Halieutic production reduction generates a subsequent fall of incomes of the households depending primarily on the fishery activities. The fall of halieutic production involves today significant migratory movements of the fishermen and socioeconomic problem. Thus, adaptation strategies are developed for sustainable management of the lake Aheme. These strategies consist in holding as sacred a part of the lake with the divinity Avlekete, fishing holes creation and mangrove restoration. Sacred lake park called ‘’Avlekete-tin’’ is the most important traditional strategy. These endogenous methods of ecological conservation constitute actually effective strategies of productivity and fishing development on the Aheme lake

Trend and variability in a new, reconstructed streamflow dataset for West and Central Africa, and climatic interactions, 1950 – 2005

International audienc

Near-term impacts of climate variability and change on hydrological systems in West and Central Africa

Climate change is expected to significantly impact on the availability of water resources in West and Central Africa through changes in rainfall, temperature and evapotranspiration. Understanding these changes in this region, where surface water is fundamental for economic activity and ecosystem services, is of paramount importance. In this study, we examine the potential impacts of climate variability and change on hydrological systems by the mid-21st century in West and Central Africa, as well as the uncertainties in the different climate-impact modelling pathways. Simulations from nine global climate models downscaled using the Rossby Centre Regional Climate model (RCA4) are evaluated and subsequently bias-corrected using a nonparametric trend-preserving quantile mapping approach. We then use two conceptual hydrological models (GR2M and IHACRES), and a regression-based model built upon multi-timescale sea surface temperatures and streamflow teleconnections, to understand hydrological processes at the subcontinental scale and provide hydrological predictions for the near-term future (2020-2050) under the RCP4.5 emission scenario. The results highlight a zonal contrast in future precipitation between western (dry) and eastern (wet) Sahel, and a robust signal in rising temperature, suggesting an increase in potential evapotranspiration, across the multi-model ensemble. Overall, across the region, a significant increase in discharge (similar to + 5%) is expected by the mid-21st century, albeit with high uncertainties reported over most of Central Equatorial Africa inherent to climate models and gridded observation data quality. Interestingly, in this region, teleconnections-based regression models tend to be an alternative to hydrological models

Assessment of Spatio-Temporal Changes of Land Use and Land Cover over South-Western African Basins and Their Relations with Variations of Discharges

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

Variabilité pluviohydrologique et inondation dans la Basse vallée du Mono (Bénin, Afrique de l'Ouest). In Ben Géo : Revue semestrielle de géographie du Bénin, N° 3, Bénin. Université d'Abomey-Calavi.

International audienc

Variabilité pluviométrique et dynamique hydro-sédimentaire du bassin versant du complexe fluvio-lagunaire Mono-Ahémé-Couffo (Afrique de l'ouest)

This thesis aims to highlight the relationship between climate and water balance process on the basin of the complex river-lagoon Mono-Aheme-Couffo. A better analysis rain/flow is made using rainfall spatialization from interpolation, taking into account altitude and geographical coordinates of hydrometeorological stations. Also, pluvio-hydrological variability and surface states dynamics impacts on sedimentation are examined. Runoff variability and sediment dynamics in the watershed Mono-Aheme-Couffo over the period 1961-2000 in a context of integrated water resources management (IWRM) were analyzed according to the rainfall depths, effects of water releases from the Nangbeto dam operational since september 1987,the dynamic of surface state and geological bedrock (crystalline basement and sandstone). Thisapproach combined the use of meteorological, hydrological, land use land cover, sedimentological data, associated with a previous studies and field observations data have enabled us to develop efficient statistical methods for achieving the objectives of this study.The results show that rainfall deficits of the 1970s and 1980s have multiplied by 4 deficit of flow, due to recharge lack. But, slight high rainfall (3%) of 1988-2000 period compared to the sub-period 1965-1987, caused an excess flow of 0.1 % on Couffo basin and 37 % on Mono basin. Effects of the dam Nangbeto result in an increase of 97 % of low flows whereas rising flows fall of 3 %. This shows the role of the dam Nangbeto on stream flow and flood reduction and consequently perpetuation of the flow on the downstream of the basin. The GR2M model proves effective enough to simulate the average flows despite the influence of water releases from the dam Nangbeto.In contrast, the low runoff coefficients and the low correlation between runoff and recharge, show that precipitation is not the only factor explaining the hydrological basin functioning, but also geological bedrock and surface conditions play also key role. These determine the suitability of soils for infiltration, runoff and erosion. From 1956 to 2000, there was a regressive evolution of natural forestland and increase of agriculture land. Human pressure on the catchments induce decrease of over60 % of the forest and savannah land, which play a moderating role on the flow, make easier infiltration and reduce sediment transport towards the rivers beds. Natural vegetation degradation could only lead to runoff and evaporation increase, decrease of infiltration and groundwater shortage and so accelerated erosion and sedimentation process.To this effect, pluvio-hydrological change linked to land use land cover change has contributed to increase of sediment transport which largest part reach the river bed during the period of high waterhold only 8 % of this time. These solid charge contributions are both marine and continental origins;the most important are drained by rivers. They have contributed to the water bodies area reduction of 4 % in the lower valley. Mono sediment inputs before the dam Nangbeto drive the lagoon system closing of 1.6 mm/year and could cause the biocenose destruction and therefore disappearance of fishstocks.L’objectif de cette thèse est de mettre en évidence la relation climat/bilan hydrologique. Pour une meilleure analyse de la relation pluie/débit, une spatialisation pluviométrique est faite à partir de l’interpolation, en tenant compte de l’altitude et des coordonnées géographiques des stations.L’impact de la variabilité pluvio-hydrologique et de la dynamique des états de surface sur la sédimentation est aussi examiné.La variabilité des écoulements et la dynamique sédimentaire dans le bassin-versant Mono-Ahémé-Couffo pendant la période 1961-2000 dans un contexte de gestion intégrée des ressources en eau (GIRE) ont été analysées, en fonction des lames d’eau précipitées, des effets de lâchers d’eau du barrage de Nangbéto mis en service depuis septembre 1987, de la dynamique des états de surface et du substratum géologique (socle et grès) en place. L’approche combinée de l’utilisation des données météorologiques, hydrologiques, d’occupation du sol, sédimentologiques, associées aux études antérieures et aux observations de terrain, ont permis de développer des méthodes statistiques efficaces pour atteindre les objectifs fixés pour cette étude.Les résultats montrent que les déficits pluviométriques des décennies 1970 et 1980 ont multiplié par 4les déficits de l’écoulement, avec pour conséquence un déficit de la recharge. Mais, avec la légère reprise pluviométrique (3 %) de 1988 à 2000 par rapport à la sous-période 1965-1987, on assiste à un excédent d’écoulement de 0,1 % sur le Couffo et 37 % sur le Mono. Les effets du barrage de Nangbéto se traduisent par une augmentation de 97 % des débits d’étiage alors que les débits de crue ont connu une baisse de 3 %. Ceci montre le rôle joué par le barrage de Nangbéto sur le débit d’écoulement et l’atténuation des inondations et par conséquent une pérennisation de l’écoulement en aval du bassin.L’utilisation du modèle GR2M se révèle assez efficace à simuler les débits moyens malgré l’influence des lâchers d’eau du barrage de Nangbéto.En revanche les faibles coefficients d’écoulement et la faible corrélation entre écoulement et recharge,montrent que la précipitation ne constitue pas le seul paramètre expliquant le fonctionnement hydrologique du bassin, mais qu’interviennent aussi le substratum géologique et les états de surface.Ces derniers déterminent l’aptitude des sols à l’infiltration, au ruissellement et à l’érosion. De 1956 à2000, on note une évolution régressive des formations végétales naturelles au profit des formations anthropiques, du fait des pratiques agricoles. Cette pression humaine a entraîné une diminution de plus de 60 % des formations de forêts et de savanes arborées, qui jouent un rôle modérateur sur l’écoulement, facilitent l’infiltration et ralentissent les apports solides vers les lits des cours d’eau.Leur dégradation entraînerait donc une augmentation de l’écoulement et de l’évaporation au détriment de l’infiltration, accélérant le déficit des réservoirs souterrains ainsi que l’érosion et donc la sédimentation.À cet effet, la variation pluvio-hydrologique, associée à la dégradation actuelle des unités paysagiques, a contribué à l’augmentation des charges solides dans le bassin, dont les plus importantes parviennent au lit en période des hautes eaux, et occupent seulement 8 % de ce temps.Ces apports sont à la fois d’origine continentale et marine, dont les plus importants sont ceux drainés par les cours d’eau. Ils ont contribué à la réduction des superficies des plans d’eau de 4 % dans la basse vallée. Avec les apports du Mono avant la construction du barrage de Nangbéto, le système lagunaire se comble de 1,6 mm.an-1 et pourrait engendrer, la destruction de la biocénose et donc la disparition des ressources halieutiques

Lutte contre l'érosion pluvial: cas de l'arrondissement d'Abomey-Calavy

National audienc

systèmes traditionnels endogènes de gestion durable du lac Ahémé au Bénin (Afrique de l'ouest).

Les plans d'eau du Bénin tels que le lac Ahémé regorge une diversité d'espèces halieutiques (poissons, crabes, crevettes, etc.) exploitées par les populations du sud Bénin. La dégradation poussée de l'écosystème du lac Ahémé entraîne inexorablement la diminution de la production halieutique. Ainsi, des stratégies d'adaptation et de gestion du lac s'avèrent nécessaires pour un accroissement de la production halieutique. Les populations riveraines, à défaut de draguer le lac, adoptent la technique de trous à poissons. Par ailleurs, la sacralisation de certains endroits du lac avec le fétiche Avlékété (appelé « Avlékété-tins » : enclos entourant le Vodoun Avlékété) constitue une autre forme de gestion du lac. Cette pratique consiste à conserver la ressource halieutique pour une pêche durable. Ce système de gestion traditionnelle est aujourd'hui approuvée par les autorités administratives et promu par le Centre d'Action Régional pour le Développement Rural (CARDER). Cette méthode de conservation écologique endogène constitue aujourd'hui une stratégie efficace de développement de la pêche sur le lac Ahémé; auquel s'ajoute la restauration des forêts de mangrove aux abords du lac pour une forte productivité