The Gnangara groundwater system in Western Australia occupies some 2,200km2, supports multiple ecological systems and human uses, and is under unprecedented stress due to reduced rainfall and over-extraction. The basin is currently managed according to command and control principles by the state's Department of Water. This paper examines some of Ostrom's "situational variables" for the analysis of institutional choice – the selfprovision of institutional arrangements in common-pool resources situations – as they relate to the Gnangara case. The paper approaches the topic of collective action not as a niche concept which may be fitted only to certain specific cases, but as a basic and natural mode of human co-operation and interaction when faced with inter-dependent interests and in the absence of militating factors. We therefore conduct the analysis from the perspective of identifying elements of the current management approach – as well as of the shared norms, expectations, and attitudes of the appropriators – which could be altered to allow collective governance to develop, at least at some scale within the overall management regime. We use data from a set of water licence documents obtained from the Department of Water, among other data sources. A number of factors are identified as inhibiting the development of collective action at present. Current arrangements are topdown in nature, with all rules, monitoring, and enforcement supplied by the state-level management agency. Current norms and expectations among the appropriators appear to be competitive rather than co-operative, and discount rates appear to be high. In view of the size of the resource, and the large number and heterogeneity of appropriators, we conclude that the use of 'nested' organisational units – beginning at the smaller scale – will be a key component of efforts to develop the requisite social and institutional capital. Further, we conclude that there are several historical and other factors in this case whose net effect is to prejudice the unassisted development of collective action institutions by appropriator efforts alone, and that significant external support will be required from government agencies. This study highlights some important aspects of the regulatory apparatus in place, their likely effects upon the resource appropriators in terms of attitudes and behaviours, and the resulting impacts on the common-pool resource upon which wildlife, ecosystems, and the appropriators all depend.