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• Grassroot collective action can lead to successful groundwater co-management. • The interaction between impacting factors and collective action is dynamic. • Human and social capitals are key to successful collective action. • Collective action needs a 2-way interaction between formal and informal institutions. Resource-user participation in decision-making, through local collective action, likely contributes to effective groundwater management and protection. Despite efforts to construct generalized theoretical frameworks explaining factors influencing successful collective action in groundwater management, this is a highly complex process that remains challenging. This paper analyzes factors facilitating and impeding collective action in groundwater management, using the rare and successful collective-action example of the Angas Bremer irrigation district (South Australia). Drawing on data gathered through semi-structured interviews this paper further explores the context under which collective action arose and changed over time. The findings show a dynamic transient interaction between the following factors responsible for the rise and fall of collective action: (i) perceived crisis, (ii) small, homogenous community (iii) strong leadership from respected community members, (iv) shared norms and values, (v) shared goals, and (vi) trustworthy two-way relationship between resource users and formal institution. Although it is difficult to generalize from one case study, collective action and groundwater management are highly contextual. These findings are useful (i) for other communities with similar characteristics, (ii) to explore conditions for achieving successful groundwater governance including efficient and effective reforms, (iii) to highlight the importance of participatory management processes, (iv) to help government agencies understand what motivates communities to engage in collective action and how that leads to successful groundwater co-management, and (v) to expand on a very small body of literature documenting stakeholders narratives on collective action and groundwater management. [ABSTRACT FROM AUTHOR]

• Storage-discharge relation of groundwater was determined by a tracer-aided approach. • Dynamics of groundwater discharge in response to precipitation were assessed. • Residence time of groundwater was quantified based on storage-discharge relations. Sustainable groundwater management is becoming increasingly important due to intensifying water deficits around the world, which highlights the necessities and challenges to explore the dynamics of groundwater at the catchment-scale. In this paper, a tracer-aided approach has been developed and applied to quantify the relationships between groundwater storage and discharge, upon which the dynamics of groundwater storage and its residence time are assessed. Robust nonlinear storage-discharge relationships are found for the eight studied catchments located in a headwater region of the Murray-Darling Basin, Australia. The dynamics of groundwater storage for all the studied catchments largely show synchronization with regional climate. The estimated highest and active groundwater storages in a year are more responsive to precipitation than the lowest storages. For all the studied catchments, during dry seasons without recharge, the depletion rate of groundwater is found to decrease with the decline in groundwater storage, which can be ascribed to the vertical heterogeneity of their unconfined aquifers. The mean residence time of groundwater represented by MRT 75 (i.e. time taken for groundwater storage to diminish from its mean level to the 75th percentile) varies between 57 and 111 days across the studied catchments, suggesting considerable hydrogeological differences among the studied catchments. The groundwater dynamics observed in this research could contribute to improving hydrogeological model performance in simulating the connection between groundwater and surface water at the catchment-scale. Moreover, the findings could serve to develop guidelines for groundwater extraction when considering the constraints of environmental flow requirements. [ABSTRACT FROM AUTHOR]