A cross disciplinary framework for linking farms with regional groundwater and salinity management targets

Irrigation delivers major benefits in food security and human development. Irrigation also leads to waterlogging and salinity which threaten the sustainability of irrigated agriculture and pose major socioeconomic and environmental risks. The issue can be addressed by limiting net recharge to groundwater such that the water and salt keep natural equilibria. Often the information on net recharge within catchments is unavailable, particularly at lower spatial scales such as the farm or paddock; this offers little guidance for on-farm land and water management decisions—basic decisions that ultimately impact regional net recharge and waterlogging and salinity dynamics. This paper develops a cross disciplinary framework based on the concept of net recharge for setting paddock scale targets and to link these to the regional targets and community's goals for sustainable irrigation management. A management model, cast in a dynamic programming format to integrate a detailed hydrological model with an economic model was applied to estimate the productivity, profitability and sustainability of irrigated agriculture in a region of the Murray Darling Basin in Australia. SWAGMAN® Farm model was used to determine paddock scale net recharge. This interactive model enables an individual farmer to choose a profit optimizing crop mix while lowering net recharge; this in turn leads to a win-win outcome for all farmers. The net recharge metric can be used for the conversion of diffuse source groundwater recharge to a point source recharge at paddock scale, enabling the definition of private property rights to a common pool problem and assigning individual responsibilities for its management—a vexing issue and a new concept for the commons literature. Net recharge shows significant spatial and temporal variation which warrants a targeted/zonal approach to address the issue. Regional and targeted strategies and actions to address the issue are identified. Apart from its applied and action research orientation, the development of paddock scale net recharge metric is perhaps the most significant conceptual contribution of this research which can lead to shared management of groundwater aquifers.