Irrigated agriculture is vital for the food security and prosperity of people in large river basins like the Murray-Darling and Mekong. Irrigation requires water-control structures in rivers, such as weirs, sluices and regulators. Many of these structures can have negative impacts on fish. However, these impacts can be reduced if structures are designed and operated in a way that is safer for fish. This report outlines the findings from a 4 year study of the hydraulic and biological performance of different irrigation weirs in both Las PDR and Australia.