This report was commissioned by Auckland Council to demonstrate how the Catchment Land Use for Environmental Sustainability (CLUES) model can be used as part of the council’s implementation programme for the National Policy Statement on Freshwater Management (NPSFM).

The NPSFM requires regional councils to, amongst other actions, set water quality limits and, where those limits are exceeded, specify targets for water quality and implement measures to reach those targets. The Ministry for the Environment working document Freshwater reform 2013 and beyond recommends the use of models in the implementation of the NPSFM to aid communication and understanding of water quality issues among a range of stakeholders, including scientists and other experts, policy makers, regulators and community groups.

This report:

• Overviews the CLUES model and associated geo-spatial data, including default land cover (based on the Land Cover Data Base for 2002, LCDB2) supplied with the model software. (Section 2.0)
• Develops two land use scenarios relating to the years 1770 (“Pre-European”) and 2008. The Pre-European scenario was created to give an insight into historical contaminant loads which are indicative of the background or natural state of water quality in the Auckland region. The 2008 scenario updates the default land use on the basis of land cover mapped in the more recent LCDB3. (Section 2.3)
• Simulates water quality using the default, updated and Pre-European land use scenarios to provide examples of how CLUES results can be extracted and displayed for either further analysis or to aid public understanding of water quality issues. In addition to regional maps, CLUES results are aggregated and displayed in tabular form by catchment for ten river catchments and three lake catchments selected in consultation with the council. (Section 3.0)
• Demonstrates the ability of CLUES to provide current state information on contaminant loads and concentrations in the Auckland region by comparing CLUES results with long-term water quality observations. Sources of model uncertainty and error are discussed and calibration needs with respect to the Auckland region are evaluated. (Section 4.0)
• Overviews proposed changes to freshwater management in New Zealand and where CLUES fits within the context of those changes. The overview presents a number of case studies where CLUES has already been applied to aid planning. Planned user-directed improvements to the model in relation to the proposed changes are also discussed. (Section 5.0)
• Discusses the scope for further work including the need for local calibration. (Section 6.0)

Auckland Council technical report, TR2015/014

May 2015