Satellite monitoring of the spatio-temporal dynamics of irrigated market garden crops in relation to collective and individual water hydraulic development : Case study of the Ouagadougou (Burkina Faso) vegetable gardening belt

In many peri urban areas of Africa, vegetable and fruits crops are expanding rapidly thanks to a fast growing market and an attractive profitability for farmers. These productions mainly grown in off season need irrigation, and water availability is then the main limiting factor of their development. In Burkina Faso a very large number of small scale dams have been built since the dry spells of years 1980 to store surface water and support irrigation. Question arise about the environmental and productive impacts of these dams as many seem under utilized. Groundwater, combined with the multiplication of individual wells and recent availability of solar powered-pumps is increasingly used for irrigation and seems a major alternative source of water. This study focuses on the off season (November – May) cropping conditions of 4 main sites of the Ouagadougou vegetable gardening belt, with comparison of two situations of farmer led development: (i) an area surrounding a small reservoir/dam, (ii) an area of lowland without reservoir. A remote sensing analysis combining a very high spatial resolution coverage (Pléiades, 0.5 m) and Sentinel 2 time series (5 days revisit frequency at 10 m spatial resolution)  is performed for mapping irrigated crop area and its monthly temporal dynamics allowing the identification of multiple crop cycles during the dry season. Coupled with climatic water balance data and remotely sensed detection of surface water availability upstream of dams, this analysis highlights the role of small dams and individual wells on groundwater availabilty and extension of the cropping period.