The majority of agricultural production systems in the GMS receive all or most of their water from rainfall, and thus are vulnerable to climate variability. There is great potential for improving productivity, sustainability and resilience in these systems, particularly by better control and use of water resources. All national governments consider expanding their irrigation to be an important priority. Irrigated areas are increasing but economic and physical constraints prevent full implementation in some areas. Upgrading rainfed agriculture promises large social, economic and environmental paybacks, particularly in terms of reducing poverty and boosting economic development.