Groundwater is essential for early-season agriculture in many arid regions. In such regions, however, groundwater recharge is generally low, leading to groundwater degradation. State responses are seldom effective in addressing this issue, which leads to fatalist narratives of the unsustainability of profitable agricultural growth and the collapse of aquifers. We argue that such narratives make it difficult to recognise more promising instances in which communities find solutions to groundwater degradation. We call for a fine-grained analysis of the social practices around the use of groundwater, which, we argue, represent a process of commoning. We do so while recognising that the collective action of communities is embedded in an intricate set of relations with other stakeholders including the state, and that the positive environmental and transformative social change that is often associated with commoning cannot be taken for granted at the outset. Building on the case of the arid Drâa Valley in Morocco where watermelon production has expanded rapidly, we illustrate how the process of commoning evolves through different social practices, including: 1) the use of new farming practices that reveal the potential of the aquifer; 2) the representation of the aquifer as severely degraded and the development of a narrative around it being a collective good to be protected against outsiders; 3) the defining and negotiating of rules to control groundwater access and use; and 4) the engagement in negotiations and the resolving of conflicts. Our analysis shows that commoning, as performed by young local farmers, is about extending the lifespan of the aquifer for agricultural production rather than preserving it indefinitely; however, an examination of commoning practices also reveals the capacity of the community to change the course of the future.