A regional hydrologic–economic evaluation to devise environmentally sustainable rice farming systems in southern Murray Darling Basin, Australia

Abstract

Waterlogging and salinity problems in major rice growing areas demand policies aimed at better management of land and water resources. This process can be facilitated through regional scale spatially distributed hydrologic–economic models that capture and integrate point scale processes at paddock, farm and irrigation area levels. The study develops an integrated hydrologic–economic framework that integrates hydrologic and economic responses for social and common pool optimum management in the Coleambally Irrigation Area, Australia. The results of hydrological-economic model indicate that the economic units with heavier soils and shallow watertables with minimum groundwater out flows are the best economic locations for growing rice as the total crop water requirements are minimised. Social and common pool optimum scenarios indicates, after accounting for externalities and groundwater dynamics, the optimal net returns could be achieved in about 15 years. There was not much difference between social and common pool optimum, however, common pool optimum show decline in net revenue after 23 years because of shallow watertable rise within 2 m of the surface. The current rice growing policies are mainly based on the clay content of soils and rice water use limits. This work has highlighted the importance of incorporating groundwater dynamics in deciding environmental policies for growing rice.