Australia's Murray-Darling Basin exemplifies complex governance challenges raised by large-scale trans-boundary river systems. The Basin contains a varied and fragmentary mosaic of human perspectives and practices, situated in a dynamic biophysical system that accounts for a significant portion of Australia's agricultural produce and is home to diverse and iconic ecosystems. Severe drought, high river-flow variability, and persistent ecosystem degradation have been impetus for water policy reforms culminating in the highly contested 2012 Murray-Darling Basin Plan. We analyzed public-record content from opinion editorials and speeches by policy elites, 2010-2012, to examine public discourses and discourse coalitions associated with development of the Plan. We focus on three domains of discourse: definition of problems, promotion of solutions, and assertions of fact. Discourses illustrated divergent, exclusionary, and largely un-reconciled perspectives about how water resources should be managed, as well as how plural interests should be represented in decision-making. We identify discourse coalition-linked narrative scripts, develop an understanding of constitutive dynamics relevant to ongoing processes of policy development and implementation, and discuss implications for adaptive governance of water resources.