Climate change is projected to substantially alter the hydrological cycles of mountainous regions, with pronounced consequences for the human settlements in these areas. Because projections of climatic changes and their environmental and societal impacts in local settings are uncertain, policies to reduce vulnerability and strengthen adaptation should be informed by ongoing processes in sites already exposed to climatic variability and change. This paper examines vulnerability to hydrological change in Northern Ecuador and shows how access to irrigation water mediates the ability of different groups of farmers to adapt. We argue that present vulnerabilities need to be understood in the context of the history of resource rights distribution in the area and that agricultural adaptation would be aided by a reform of current water rights, allowing water resources to be more equitably distributed.