Incorporating weather forecasts into risk-based irrigation decision-making

ABSTRACT Irrigation decision-making is complex. It requires balancing multiple risks . We examined if incorporation of weather forecasts into irrigation decision-making improved environmental and economic outcomes on dairy farms in Canterbury, New Zealand. We focused on understanding how farmers can manage irrigation decision-making with uncertain weather forecasts, and the associated impacts on drainage, pasture growth and economics. Previous work had demonstrated that weather conditions were not used in irrigation decision-making as much as desirable and that weather forecast uncertainty was not explicitly considered. , We incorporated weather forecasts as a perfect forecast and the best available forecast. We used probability percentiles to incorporate forecast uncertainty into decision-making. The research hypothesis was that through utilising risk profiles of factors that influence environmental and economic outcomes of irrigation decisions, farmers could improve decison-makingwhen faced with uncertain future weather states. When weather forecasts were integrated into irrigation decision-making, there were environmental and economic benefits relative to a simple deficit-based irrigation decision rule. Based on a case study, we predicted 5% additional profit (approximately, $200 per hectare) may be possible when the best available forecasts was used relative to a simple deficit-based decision rule, and a further 1% profit if forecast uncertainty was considered.