The Waikato River system is New Zealand’s longest river and has significant spiritual relevance for the Waikato-Tainui people and other river iwi, who regard it as an indicator of their mauri or well-being, and central to their identity. The Waikato has also been the focus of on-going tensions between Māori cultural and spiritual values and beliefs, and national engineering objectives. The Waikato River was the primary source of food, transportation and communications link for the region and of pivotal military significance in the New Zealand land wars of the 19th Century. The river system is also a strategic asset for power generation and the flow has been extensively modified with the engineering of dams, lakes, tunnels and canals used to generate one sixth of New Zealand's total electrical generating capacity via the Waikato and Tongariro Power schemes. Large scale deforestation in combination with altered hydrologic characteristics have resulted in siltation of the once navigable river. The Waikato is impacted upon by numerous sources of pollution including; Arsenic from a Geothermal Power Station; nutrient enrichment from fertilizer and effluent spreading practices in dairy farming; more than 80 point source discharges to the main stem; and 1,600 discharges to its tributaries. The river system contains numerous fish types and has an international reputation for fishing. More than twenty communities extract and treat its waters for potable use including Auckland City. Historic practices resulted in significant adverse impacts on water quality and the mauri of the Waikato. The river is now administered by a regional council. These attributes make the Waikato River a complex management challenge: a contemporary relevance of the widely known metaphor; Waikato Taniwharau (Waikato with hundreds of guardians). Aotearoa New Zealand is currently resolving policy issues for the effective management of its fresh water resource. A national survey of opinion in 2005 distilled public priorities for fresh water management. The Freshwater for a Sustainable Future consultation identified many concerns and that the management of these resources is not being carried out in a sustainable manner. The Land and Water forum acknowledged many of these issues in the National Policy on Fresh Water (2010). The New Zealand government is currently preparing to sell down its 100% control of the hydro generation assets on the river, through a sale of shares in the State owned Enterprises that manage these assets. During the initial public consultation, responses from Māori, the indigenous peoples of Aotearoa New Zealand, indicated that there existed significant dissatisfaction with past management and a lack of confidence in future policy and water management decision making. The dissatisfaction manifested as broad opposition to and indifference towards participation in consultation. In subsequent years, some Māori groups have nevertheless chosen to engage in research processes seeking improvements on past practice. A Decision Making Framework (DMF) developed in 2004 has been adopted in several of these proposals due to its ability to balance the competing priorities of engineers representing the dominant western worldview and Māori, the Tangata Whenua (people of the land). The Mauri Model DMF is unique in its approach to the management of water resources as the framework offers a transparent and inclusive approach to considering the environmental, economic, social and cultural aspects of decisions being contemplated. The Mauri Model DMF is unique because it is capable of including multiple-worldviews and adopts mauri (intrinsic value or well-being) in the place of money based assessments of pseudo sustainability using Cost Benefit Analysis. The Mauri Model DMF does this using a two stage process that first identifies participants’ worldviews and inherent bias regarding water resource management, and then facilitates transparent assessment of selected sustainability performance indicators. The assessment can then be contemplated as the separate environmental, economic, social and cultural dimensions of the decision, collectively as an overall result; or the priorities associated with different worldviews can be applied to determine the sensitivity of the result to different cultural contexts or worldviews. A sustainability assessment for the Waikato River is presented within the context of new co-management aspirations that require decision making to reflect the values of both the Government and the Waikato-Tainui peoples. How might the Mauri Model contribute in the complex context of co-management of the Waikato River? Three existing resource uses are assessed to illustrate the contribution that alternative frameworks can make to an enhanced understanding of the challenges that the new co-management regime will need to overcome.