Water productivity became an important issue in improving the performance of irrigation, including when focusing water saving issues. However, various concepts may be considered, which requires appropriate definitions and related analysis. Because it represents a ratio between harvesting yield and water use, a main component of the latter is crop evapotranspiration. This calls for a discussion relative to its concepts and computation, thus to identify both how crop evapotranspiration may be managed to improve water productivity and existing gaps in its knowledge. In addition, a discussion on the economic aspects relative to improved water productivity and saving is presented, including a simple analysis of economic issues and respective gaps in knowledge.