A Farm Scale Hydrologic Economic Optimisation Model To Manage Waterlogging And Salinity In Irrigation Areas

Abstract

Large parts of the irrigation areas of the Murray Darling Basin have shallow watertables that threaten crop productivity and financial sustainability of irrigated agriculture due to soil salinisation and waterlogging. Planning for environmentally sustainable and economically viable management of these problems requires the development, testing and application of mathematical models which can integrate our understanding of water and salt movement with economic assessment of different cropping decisions at a farm scale. These mathematical models can help in proper selection of agronomic and engineering options to reduce recharge to aquifers and rise of watertables and thereby minimise waterlogging and salinity problems. This paper gives mathematical details and sample applications of SWAGMAN (Salt Water and Groundwater Management) Farm, a farm scale hydrologic economic model that integrates agronomic, climatic, irrigation, hydrogeological and economic aspects of irrigated agriculture. Optimum land uses for a given farm are determined by optimising an economic objective function using mixed integer non-linear optimisation techniques. SWAGMAN-Farm has been applied to several farms in irrigated areas of southeast Australia. Model results show that for given hydro-climatic and irrigation conditions some land use types result in overall discharge from soil and groundwater while others induce groundwater recharge: a proper selection of crops can help reduce waterlogging and salinity problems and ensure economic viability of farms.