Legitimacy in polycentric groundwater governance: Framework conditions identified in <scp>Nebraska's</scp> Natural Resource Districts

Abstract This study considers how and why agricultural groundwater users would limit their own water consumption. We find that voluntary governance arrangements are based on a form of legitimacy that stems from informal social processes. Agricultural irrigation reform in Nebraska, U.S. took place after decades of collaboration in informal social settings; this background of decentralized rulemaking contributed to legitimizing extraction limits in times of water stress. The dimensions of social legitimacy are assessed through triangulation of interview data, integrated management plans, workshop facilitation, and recordings of legal proceedings related to the Natural Resources Districts in the state of Nebraska. These districts initially placed voluntary limits on extraction but evolved to sanction violators for over‐consumption. Groundwater rules are accepted because they are set by publicly elected boards, leaders participate in a state‐wide leadership training network, and the districts are granted rule‐making authority by the state. Our results show that voluntary self‐limiting behavior can form the basis for binding legal requirements. The legitimacy of polycentric governance stems from social acceptance, inclusive membership, a prior history of collaboration, and an understanding of rules. The rules themselves are context‐specific and self‐made. We summarize these elements in an evaluation framework to test whether and how authority in other polycentric groundwater governance arrangements is justified and accepted.