This report offers a guide on potential reform pathways towards sustainable agriculture water use, based on a thorough review of selected past water and agriculture reforms and extensive consultation with policy experts. A theory of change is developed that emphasises the importance of flexibility in the timing and design of reform processes to achieve practical and effective policy changes. Governments should prepare future reforms, via continued research, education, and governance efforts, to help take advantage of reform opportunities when the timing is right. Five necessary conditions are identified for a successful reform process: (i) support evidence-based problem definition, objective setting and evaluations; (ii) ensure that governance and institutions are aligned with the policy change; (iii) engage stakeholders strategically and build trust; (iv) rebalance economic incentives to mitigate short run economic losses; and (v) define an adjustable smart reform sequencing that provides flexibility in the long run. These conditions are found to be necessary to implement four challenging policy changes: charging water use in agriculture; removing subsidies that negatively impact water resources, regulating groundwater use and addressing nonpoint source pollution. But the relative effort that governments need to devote to fulfilling each of the five conditions will vary depending on the policy change.