Climate change and rainfall variability has increased the reliance upon groundwater sources in many irrigation districts in Australia. Groundwater extraction for irrigated agriculture in the Murray-Darling Basin has significantly lowered water tables, increased pumping costs, disconnected groundwater and surface water, and impacted dependent ecosystems. Water reform since the late 1990's has cut groundwater irrigators entitlements. In the Namoi Valley in NSW, the largest groundwater irrigation district in the Basin by volume, these cuts represent 80% of initial entitlements. Improved on-farm water efficiencies are potentially a key strategy to enable farmers to adjust to reduced entitlements and minimise economic and social impacts. Adaptation measures for the Namoi irrigators include modifying flood irrigation practices by more precise timing and application of water, changing from flood to overhead spray irrigation, and deepening dams to reduce evaporation losses. Research that estimates the extent of water savings if farmers adopted best-practice has failed to consider adoption rates of such practices. From data provided by 210 irrigators in the valley for the 2010-2011 growing season, we identified those farmers likely to adopt water saving practices and estimated water savings. Farmers who were likely to adopt these technologies could save the region up to half the water to be cut from entitlements. Therefore, a relatively small number of on-farm water saving technologies could substantially contribute to, and limit negative economic and social impacts of, water reforms. Efforts to engage farmers in practice change to achieve on-farm water savings should target those more likely to adopt those practices.