This article shows that the impacts of mining interventions on communities and their water resources go beyond quality and quantity features; mining profoundly reconfigures customary and formal water control arrangements around, among, and within rural communities. It demonstrates the inherent contradictions that accompany these reconfigurations, many of which happen through processes of formalizing water tenure relations. Although formalization, as a state-endorsed legal instrument, may provide security to some user groups and communities by officially recognizing their uses, it also inevitably introduces new political-normative hierarchies between communities and, at the same time, erodes existing water sharing and management arrangements. The article illustrates these contradictions through an examination of the interactions between communities, the state, and the Las Bambas mining company in Apurimac, Peru. It highlights how new claims to water provoked by the mining company generate tensions with rural communities' existing water management arrangements, ultimately threatening to make them and the logics upon which they are based disappear. A better understanding and consideration of actually practiced local water arrangements can lead to more respectful policies towards rural communities and help reduce tensions among water users in contexts of mineral extraction.