ENSO-based streamflow forecasting and its application to water allocation and cropping decisions - an Australian experience

Abstract

High climatic variability in northeast Australia, combined with limited water resources and increasing demand, makes the task of managing irrigation water and cropping decisions more complex. In this paper we explore the relationship between the El Niño-Southern Oscillation (ENSO) and the Inter-decadal Pacific Oscillation (IPO) on long-term streamflow. A functional relationship for forecasting streamflow and water availability will allow improved management of water resources and cropping decisions. Our results show that streamflow can be forecast during the peak irrigation demand period (October–January) using the Southern Oscillation Index (SOI) up to four months in advance. The impact of ENSO on streamflow is modulated by IPO phases with a substantial strengthening of La Niña episodes during the cold (negative) phase of IPO. Simulation of dam inflow and water allocation shows that the volume of irrigation water in La Niña years is significantly more than that in El Niño years; the resulting increase of some 20% in total crop area has a potential revenue of Au$40 million in the study catchment. Economic analysis using gross margin shows that SOI-based planting strategies would result in the best economic return for cotton growers in this region.