Dynamic Adaptive Pathways Planning for a Water Resources Investment Strategy
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G. Williams (Wellington Water Ltd), J. Reed, R. Menke & E. Benn (Beca Ltd), J. Lawrence (PS Consulting & Te Herenga Waka, Victoria University of Wellington), S. K. Singh (National Institute of Water and Atmospheric Research), G. Darch (Anglian Water) & A. Allan (WSP).
Water utilities around the world are facing long-term challenges to the supply / demand balance from future uncertainties such as climate change, technology change, population growth and reduced abstractions, in order to protect or enhance environmental values. Water utilities, such as Wellington Water Ltd (WWL), have started on the journey to develop long-term investment strategies and inform key decisions in a dynamic and adaptive way.
The Wellington metropolitan water supply currently operates to a 1 in 50-year Level of Service for drought and is facing challenges including high water loss, future population growth and the requirement to integrate Te Mana o te Wai, to increase cultural and environmental flows. The current 1 in 50-year Level of Service is not being met and there is elevated risk of supply shortfall. This paper sets out and discusses the process undertaken by Wellington Water to address these issues. A Dynamic Adaptive Pathways Planning (DAPP) approach was developed to investigate and address these issues over a 30-to-100-year timescale. This paper discusses the challenges of:
• Understanding the implications of uncertainty in variables such as climate change impacts on rainfall, sea level rise, population growth and environmental regulation on investment decisions within the context of NZ water resource planning,
• How these uncertainties can lead to outcomes where planning strategies fail to meet the target objectives, and
• The impact of changing fundamental assumptions, such as the drought Level of Service or achieving water quantity objectives set out in Te Mahere Wai o Te Kāhui Taiao (Te Kāhui Taiao, 2021) on the investment plan and the subsequent timing of actions.
We also compare the approach taken by Wellington Water with those taken by water utilities within the UK regulated water industry for example Anglian Water – which has adopted a Multi-Objective Robust Decision-Making (RDM) approach to water resources planning.
We show how a dynamic adaptive pathway can be clearly communicated to stakeholders, how it can be used for investment planning and how monitoring can be integrated to track achievement of strategic objectives.