Hydro-climatic and Economic Evaluation of Seasonal Climate Forecasts for Risk Based Irrigation Management

Abstract

This work is focused in the Murrumbidgee catchment to help understand the value of the seasonal forecasts to rice based cropping systems. The key activities of this project include: • An overview of water allocation in the Murrumbidgee Valley • Evaluation of commonly used seasonal forecasting methods used to predict rainfall • Development of a novel water allocation model on the basis of seasonal forecasts and historic allocation data • Economic analysis of the benefits from better irrigation forecasts in irrigated catchments The key findings include: • The current system of announcing allocations does not take into account seasonal climate forecasts of rainfall and flows in the catchment. End of the season allocations are made too late and pose a serious financial risk to farmers due to inadequate information being available at the start of the summer cropping period • The SST correlations with inflows to dams has provided promising results, which can be used to forecast flows to dams with lead times of around 1 year • Artificial Neural network (ANN) approaches which can learn from historic model simulations and SST predictions can be a way forward to link climate forecasts with risk management. Results of the ANN model show good correlations with the historic water allocation trends over any given season. This tool can be used to make informed cropping risk decisions • Irrigators utilising allocation forecast information can minimise the opportunity cost of forgone agricultural production. Undertaking decision analysis, it was estimated that the net benefit of allocation forecasts to the irrigators of the CIA is between $50,000 and $660,000 per year (equivalent to $0.68/ha and $8.56/ha). This was assuming that the CIA irrigators are collectively risk averse as their risk preference is unknown As part of this project a stakeholder workshop on climate variability, climate change and adaptation in the Murrumbidgee Basin was organised, to examine research ideas on climate research for efficient irrigation management. Participants included a number of interested participants from irrigation companies, NSW Agriculture, Department of Infrastructure Planning and Natural Resources (DIPNR), Murray Darling Basin Commission (MDBC) and the local community. There is a tremendous interest in climate and water issues due to the recent drought. The farming community needs tools which can link climate forecasts with smarter agricultural water management using a risk based approach. The key barrier to the adoption of existing climate forecast tools is their lack of proven utility and the risk adverse attitude of water allocation agencies.