Collaborative governance has been widely adopted since the early 2000s to manage complex natural resource issues, such as water quality and land degradation. Most research has focused on the main features and potential benefits of collaborative governance. However, few studies have studied how collaboration facilitates (or limits) implementation of natural resource planning policies, such as water planning. Studying how collaborative governance works during implementation sheds light on how the environmental outcomes are achieved. This research uses the Great Barrier Reef as large case study of water quality, which was implemented through six regional collaborative governance efforts. The Reef is one of the most important marine ecosystems of Australia. Water quality remains one of the main threats to the Reef's environmental health and resilience. Since the beginning of the 21st century, collaborative governance approaches have been adopted in the Reef's water quality planning to improve water quality conditions. Drawing on document analysis and semistructured interviews with key stakeholders, the study shows how nested collaborative governance arrangements operated in the achievement of environmental outcomes. Although the nested regional level of collaboration proved to be a useful spatial scale at facilitating reductions of land-based runoff, the environmental outcomes achieved were moderate due to collaborative issues with state and federal levels, the powerful actors of the collaborative arrangements. This suggests the importance of improving collaborative processes within the nested governance approach (i.e., deliberation between the main actors on the policy instruments or collaborative "tools" for plan implementation).
