The Optirrig model for the generation, analysis and optimization of irrigation scenarios: rationale and scopes

The chronicle of irrigation decisions and constraints controls the necessary plot-scale crop production, at the risk of affecting regional-scale resource availability and competing usages. Preserving this fragile equilibrium certainly demands the establishment of adaptive irrigation strategies, to be decided from the fine temporal dynamics of soil reserve fulfilment by rain. The classical irrigation optimization issue is to produce more than a target yield, with as little irrigation as possible, seeking the maximal benefit. Now there is a clear incentive toward so-called deficit irrigation but its viability requires a carefully-dimensioned financial reward to compensate production losses. Whatever the assigned objectives and variables of interest, Optirrig allows to evaluate the merits, drawbacks and relevance of irrigation logics and strategies then to generate new, context-dependant and alternative scenarios. The model relies on a parsimonious description of soil water budget, plant growth, properties and biomass production to rather place emphasis on plot-scale water management.