RESUMELe développement des ressources en eau du sous-bassin du lac municipal de Dschang suscite un intérêt croissant. En prélude à l'élaboration d'une stratégie de gestion durable de l'eau du sous-bassin, un état de lieux a été réalisé et les effets des variations climatiques sur les ressources en eau analysés. Les données climatiques sur la période 1978-2008, les données secondaires des études antérieures et les données des prélèvements en eau effectués par la Camerounaise des Eaux ont été analysées. Ces données ont été complétées par des informations observées sur le terrain et collectées lors des entretiens avec des acteurs clés. Les ressources naturelles en eau de surface ont été estimées à 24 Mm 3 . Seulement 2% des eaux de surfaces sont prélevées (0.48 Mm 3 ), tandis que la capacité du seul réservoir dans le bassin est de 0.45 Mm 3 . Il y a un potentiel d'usage pour la production hydroélectrique en aval du réservoir. La qualité microbiologique du lac laisse à désirer pendant certaines périodes de l'année. La pluviométrie montre une tendance à la baisse d'environ 2% comparée au module interannuel. Les principaux problèmes identifiés sont la faible coordination des acteurs impliqués dans la gestion, l'envasement de la retenue et le manque de données fiables pour une meilleure prise des décisions. Pour une gestion durable, une approche holistique basée sur les principes de la gestion intégrée des ressources en eau devrait être adoptée.
Rice is consumed by billions of people in the world and it is estimated that over 75 percent of the world's rice is produced using continuous flooding water management practices. Studies indicate that continuous flooding has numerous disadvantages like low water use efficiencies and high emissions of methane. In order to ensure food security faced with the increasing competition for water and also to mitigate climate change, it is desirable to propose alternate water management practices to farmers. A study was carried out in Cameroon to compare the performance of local varieties of rice under different water management practices. The objectives were to: evaluate the effect of different water management practices on the growth and yield of three local rice varieties; and to determine the effect of various water management practices on the water use efficiency and water productivity of irrigated rice. Four water management regimes (continuous flooding maintained at a depth of 3 cm, intermittent flow at depths of, 3, 5 and 7 cm) and three local rice varieties were tested in a split-plot design with three replicates. The main plot factor was water management regime and the sub-plot factor, variety. The study indicates that the various water management practice do not significantly affect plant height (p>0.05). The varieties were significantly different in plant height (p<0.05). There was a significant (p<0.05) interaction between water management regime and variety on plant height. Between 39 and 47 % of the irrigation water used under continuous flooding as is practiced by most farmers in sub-Saharan Africa can be saved by the adoption of intermittent irrigation at 3-5 cm depth. The water use efficiency in intermittent irrigation with an application of 3 cm is about 100 % greater than that in continuous flooding irrigation with the same depth. For intermittent irrigation with a depth of 5 cm, the improvement is about 80 %. Intermittent irrigation produces yields which are not significantly different from continuous flooding irrigation but with a water use efficiency of up to 100 % higher. Intermittent water application with a depth of 3 cm had a water productivity of about 88 % higher than that obtained with continuous flooding irrigation. Intermittent irrigation with applied depths of 3-5 cm should therefore be promoted in sub-Saharan Africa to ensure food security while at the same time mitigating climate change through reduced production of methane.
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