Water governance remains a challenge for human societies, especially when the variation in resource inflow is large and the resource users are heterogeneous. We analyze with a coupled social-ecological systems (SES) model how socioeconomic and environmental changes affect the resilience of social norms governing resource use. In our model, agents have access to water as a common-pool resource and allocate it between rainy and dry seasons. While it is socially optimal to save water for the dry season, it is individually optimal to take water immediately. In our model, punishment of norm violators is the mechanism that may sustain cooperation. We show that the resilience of social norms could be affected by changes in socioeconomic and environmental conditions. Particularly, we find that social norms may collapse in times of resource scarcity and variability, especially if several drivers act in concert. Finally, we find that user heterogeneity in the form of different skills and inequality in land endowments may undermine cooperation. This implies that climatic changes and increased inequality – both potential drivers in the field – may affect community resilience and may lead to an erosion of social norms.