When waste water becomes solution for urban agriculture… Case study in Ouagadougou (Burkina Faso)

International audienceBurkina Faso is faced by an increase of droughts since 1970’s, even if floods are also recurrent: rains are more sparse and torrential, due to the climate change. In this context, water becomes a higher problem, particularly for farmers, who constitute 80% of the people in employment. At the same time, the country knows a rural exodus, which contributes to increase the pressure on the water resource in cities, especially in Ouagadougou. Yet, cultivated areas extend, even when they need great quantities of water and increase the pressure on the resource too. How farmers achieve to cultivate in this context of water rarefaction? What strategies are set up for water access and by who? In the framework of an interdisciplinary research program (funded by the national Network of human sciences House in France), we studied urban agriculture in Ouagadougou, associating different sources: field surveys, non-participative observations, interviews of farmers and public managers and analysis of official documents. In this proposal, we focus on the results we obtained about the strategies set up for water access, in spots of market gardening – the main agriculture category in Ouagadougou.First, we have to specify the context, in which the strategies are set up. Indeed, agriculture in Ouagadougou, like in other African cities, is faced to another difficulty: it is not recognized as an urban activity. Consequently, farmers are not supported by authorities and they set up alone their strategies to develop and even maintain their activity. The access to water resources is crucial for them and solidarity can be observed at the occasion of irrigation works, more than for other activities. The water access influences the localization of cultivated lands, what confirms its importance. First, these plots were localized near dams. Nowadays they also appear near canals. These two sources can be associated in some sites and completed by a third one: water is extracted from wells too. Here appear the strategies set up by farmers: they multiply water sources, using all they can find. They cultivate at the nearest and thus even in dams and canals, when water becomes sparser and goes away during the dry season. They also adapt sometimes their crops to the water availability, choosing others during the rainy season, when their spots are flooded. But the most original strategy for water access is the use of the canals water. Indeed, theses canals collect rainwater but also waste water, poured out by households and industries. This water has the advantage to be fertile and thus provide nutrients to soil, which is not very fertile in Ouagadougou. But it has a great disadvantage to be contaminated by bacterium, metallic and chemical elements. It is used without preliminary treatment and can thus contaminate crops, becoming then a source of risk for the public health. This strategy coming from the bottom is interesting because it is a solution facing water rarefaction in a climate change context, providing a new source of water. But it needs to be improved to go beyond its limits, maybe thanks to the phytoremediation, what we begin studying