Operating irrigation systems when water supplies are insecure is a critical challenge for both farmers and managers. The aim of this paper is to analyse how farmers adapt to water scarcity and to investigate to what extent individual farmers' practices affected the management of a community‐managed irrigation system in an area with perennial citrus orchards in northern Tunisia. Results revealed a wide range of farmers' strategies and practices aimed at maximizing their access to surface water and groundwater according to their ability. But this resulted in increasing inequity, because the biggest farmers managed to access groundwater or practised drip irrigation, while the vulnerability of small farmers increased. In this context the introduction of drip irrigation has not led to water saving. These findings should encourage the adoption of fair collective rules that account for water scarcity and farmers' diversity. Copyright © 2017 John Wiley & Sons, Ltd.