The aim of this work is to evaluate the sustainability of water management for agriculture in a specific territory through the creation of a synthetic index resulting from the aggregation of multiple indices (environmental, economic, and social). The resulting synthetic index can be used to set sustainability standards and to guide the choices mandated by the Common Agricultural Policy 2023–2027. In this work we intend to show how the Multiple Criteria Decision Analysis (MCDA) method facilitates a complex process such as establishing a degree of sustainability in a certain area and, therefore, provides support to national or regional policies and communities. The integration of MCDA and GIS increases the efficiency of the support activity. A case study is presented evaluating the level of sustainability in the Irrigation and Reclamation Consortium of Piacenza and Emilia Centrale, in the Emilia Romagna region.