MODELLING THE COST OF IRRIGATOR RESPONSE TO SALINITY IN THE LOWER RIVER MURRAY, SOUTH AUSTRALIA

This paper analyses irrigator water demand and profit changes across varying annual water availability, crop water requirements, and river salinity conditions for irrigation activities along the South Australian portion of the Lower Murray. The results of the analysis indicate that where the salinity level of the irrigation water is particularly high, purchasing and leaching additional water, over and above the amount determined by the irrigation technology and management regime, may increase overall farm profit by avoiding potential salinity damage on certain horticultural crops. The mathematical programming model used to determine the results gives irrigators a choice between accepting yield losses (for particularly high salinity levels), and purchasing and applying additional water above the minimum requirements (similar to applying irrigation water inefficiently) in order to avoid possible salinity damage. The model then maximises the irrigator's profit subject to land, water and technology constraints to find the irrigators optimal response to rising salinity. The model, given the availability of the data, could be applied to any other region that is facing rising levels of irrigation water salinity to determine the optimal response of irrigators and the associated change in irrigation water demand.