Evaluation des performances techniques de l'irrigation au Burkina Faso

In Burkina Faso, faced with the persistence of severe climatic conditions that compromise mainly rain-fed agricultural production, the development of irrigation appeared as a promising alternative to secure, intensify and increase sustainably agricultural production.
However, one of the main constraint to irrigation development is the availability of water, scarcity or shortage of water on irrigated areas.
This research contributed to the reflection on the problem of water on irrigated areas in Burkina Faso through the evaluation of the technical performance indicators, the irrigation management analysis and the irrigators organizational efficiency, while first examining the general context of the development of irrigation.
The study shows that overall, relatively large quantities of water fall in Burkina Faso. However, the distribution of this water in time and space is very uncertain and does not guarantee a good rainy season for agricultural production. The implementation of water harvesting techniques and the practice of supplemental irrigation would help secure agricultural production during the rainy season. This random rainfall context justifies the choice of producers and policies to develop irrigated agriculture.
Irrigation in Burkina Faso is essentially gravity and is poorly developed, with 33% of areas developed on an irrigable area of 233,500 ha.
Efforts are made in the construction of irrigation infrastructures. However, irrigation management is poorly controlled and producers poorly organized to ensure the proper management of water and the maintenance of hydraulic infrastructures.
Furthermore, if the water used for irrigation does not present any risk for crops and soil, on the other hand, poor management of fertilizers and pesticides has been highlighted, which could have negative consequences for the environment in more or less long term.
In order to evaluate irrigation performance, a bibliographic synthesis allowed to review and clarify the concepts of water use efficiency and productivity according to their fields of application as well as the irrigation systems and the tools to be used for best management of irrigation.
The results show that water application efficiencies were less than 20% at Savili, and between 41 and 55% at Mogtédo. Water use efficiencies ranged from 1.12 to 3.4 kg m-3 for Allium Cepa (onion) in three networks, 0.31 kg m-3 for Zea mays (corn) at Mogtedo, and 0.34 kg m-3 for Phaseolus vulgaris (green beans) at Savili.
The modeling of the theoretical and actual irrigation schedules shows that, compared with the theoretical irrigation schedule, the actual schedule in the typical and illegal irrigation networks applied irrigation too often, with crops receiving water long before they had exhausted the available soil-water supply. The amount applied was similar at the two sites (58 mm in the Savili and Mogtéto Typical network, respectively, and 43 mm in the Mogtédo illegal network) and the method of irrigation was also similar (filling furrows or small basins).
Poor irrigation management resulted in significant water loss, estimated to be 2,999,923 m3/year for the Mogtédo and Savili sites. The main reason for this underperformance seems to be related to technical and organizational failures by producers.
This study highlights the waste of water for irrigation and the strong water competition between typical and illegal irrigation networks. Thus, the problem of water on the irrigated areas in Burkina Faso is not directly related to the lack of water but especially to the poor water management.
Improving the performance of irrigated areas around small reservoirs may require:
- strengthen the technical, organizational and operational capacities of farmers;
- improve the technical quality of land development;
- privatize the water supply of the irrigated perimeters, so that the farmer benefits from the water service.