This report provides the findings of Phase 1 for the Goulburn Broken irrigation area and seeks to identify likely ecological risks associated with irrigation systems in the Goulburn Broken catchment. A list, and brief description, of likely ecological consequences of development in the catchment on which irrigation is likely to have a significant impact was developed at a workshop with relevant catchment stakeholders. Priority risks, or ecological consequences, identified included increased occurrence of blue-green algae (eutrophication); reduced native fish abundance and diversity (fish kills); spread of aquatic pest plants and animals; loss/decrease in structure and function of terrestrial/floodplain vegetation communities. Conceptual models for each of these ecological consequences have been developed. A qualitative ranking of these consequences was undertaken based on its importance in the catchment, the impact of irrigation, the probability of the consequence occurring and the scientific knowledge of the consequence. The ranking can be undertaken quantitatively when better data is assembled.