The paper presents an application of the new version of the 'Decision Support for Irrigated
agriculture' DSIrr designed to integrate water and agricultural policy analysis and to support
participatory decision process. The tool is a scenario manager for bio-economic farm models
considering climatic, agronomic, hydraulic, socio-economic and environmental aspects. The paper
offers some insight on the decomposition approach adopted to integrate economic analysis at different
scales by illustrating a case study conducted in Italy to support an ex ante evaluation of a water
management system reorganisation. Reduce water consumption is a strategic objective which pricing
policy cannot address given technical constraints. The replacement of the existing low-efficiency
irrigation system could be the solution, but the recover of cost creates an affordability problem.
Results suggest that a dual network, integrating agricultural and rural urban sectors, represents a
real challenge for the Irrigation Board since this option meets the environmental goal and pass the
economic sustainability test