Factors explaining on-site irrigation performance variability in Triffa's irrigated perimeter (East-Morocco)

Feltz, Nicolas [UCL] Vanclooster, Marnik [UCL]

Irrigated agriculture remains the largest consumer of global freshwater resources, and improving water management in irrigated agriculture is a key issue to solve the global water and food crisis. The design, planning and improvement of irrigation often rely on the assessment of irrigation performance (IP), using efficiency indicators. However, the use of the efficiency concepts can lead to misinterpretation and is frequently criticized. Moreover, they only include technical, on-site and time-specific considerations, while socio-economical issues, management and scale effects are neglected. Actual performances are then likely to be more variable than considered, and this variability must be quantified. In this research, we aim to assess and model technical irrigation performance for the Triffa’s irrigation perimeter in East Morocco. The objectives are to characterize the irrigation long term technical performance and to analyze the variability of this performance in terms of technical, agronomic and socio-economical parameters with a particular attention devoted to the associated uncertainty in order to improve the scaling relationships of performance. For meeting the study objectives, background data (land use and land use pattern, soil data, topography,..) were collected. A field survey and farm field questionnaire allowed characterizing the irrigation practices in the subregion and collecting additional field data for performance evaluation. The data collection step was followed by a modeling step, allowing assessing i) the technical irrigation performance, ii) the uncertainty associated with the irrigation performance evaluation and iii) the factors and processes explaining the variability of assessed performance. The results show that IP, when including irrigation management practices, is much more variable than usually considered. Observed performance variability is related to total amount of irrigation water applied over the year, which can itself be linked to many factors. Some of these are agronomic or technical, such as application technology or cropping pattern, but other are socio-economical and even nearly psychological. This study indeed shows that, in the study area, IP variability is linked to farm size when drip irrigation is practiced and to both crop and "citrus area to farm area" ratio when traditional surface irrigation is. Those sometimes surprising relationship can be explained by case specific issues, highlighting the need to include such socio-economic considérations into the irrigation evaluation process. The developed method, based on the water balance, can be performed with widely available data.