Water supply resilience

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Due to our geography and water source locations, the Wellington region is vulnerable to the risk of supply interruption being prolonged in the event of a major shock to the water network.

A major earthquake could severely damage the Wellington region’s water supply pipelines and water treatment plants, resulting in a shortage of water. Widespread damage of the reticulation network (the pipes that take water from major trunk pipes to taps) could take many weeks to repair.

The Wellington region has three water supply plants serving an approx. 1400km2 area; the water network has long supply lines that cross known earthquake faults.

Christchurch by comparison has 55 water supply plants serving a slightly larger area; the water network has short supply lines.

The implications for the Wellington region are that on current estimates, it could be up to 70 days before normal supply to most areas, on which business-as-usual productivity depends, is restored. For some areas, such as East Wellington, it could be up to 100 days before full water supply services to households are restored.

Economic risk

If it takes too long to return to a business-as-usual economic state, many of the professional and public services in the Wellington region that are not inherently tied to this geography may leave and not return, which creates a significant long term economic risk for the whole region.

The region is inherently interdependent in respect of the water network. For example, while normal water supply to households in the Hutt Valley might be restored relatively quickly following a major shock, many workplaces in the Wellington CBD or other areas may not have normal water supply restored for 70 days. This may lead to those businesses relocating out of Wellington, in turn affecting livelihoods in the Hutt Valley.

Our approach to improving the resilience of the Wellington Region’s water network

Given the long term economic risks to the whole region of such a prolonged period without normal water supply to enable people to get back to school, work, and play, Wellington Water proposes that the region agrees on a shared goal to work towards a situation where water supply to households and businesses would be restored from about 30 days (rather than 70 days).

With a shared goal established, the focus can shift to how to achieve that goal. A number of key projects have already been identified and further planning is under way. While there is already funding allocated to some projects that will improve the resilience of the region’s water network, the next question will be whether there is a need to accelerate the overall planned programme of activity long term and how to fund this over time without compromising each local authority’s ability to deliver against other areas of responsibility. The outcome of these deliberations will be reflected in each of the local authorities’ Long Term Plans, which will be out for public consultation mid-2017. 

Working with others

The region’s overall resilience also depends on other critical infrastructure, including roading, electricity, and telecommunications. Wellington Water is working with these other providers of critical infrastructure to ensure that individual plans for improving our respective networks’ resilience are strategically integrated and will maximise efficiencies. Through such an integrated approach, underpinned by regional stakeholder alignment on what we are trying to achieve, we can speak as a unified single voice with central government about its contribution to building regional resilience to mitigate risks to GDP from loss of productivity following a major shock.

Supplying critical users

Another major part of the equation in improving the region’s overall resilience is critical users (e.g. hospitals) and businesses having their own water storage for up to seven days, as well as having other infrastructure contingencies in place. Critical to this is a shared understanding of the cost/benefit advantage of investing in their own water storage for up to seven days, compared to funding their share of public water infrastructure improvements to a higher level of service (for example, where public water supply can be relied on after three days). Wellington Water and other infrastructure providers are engaging with critical users and businesses to build this understanding and to work with them on improving their own contingency plans. 

Similarly, the region will become increasingly more resilient the faster individual households act on the recommendation to have sufficient water storage to supply themselves with water for up to seven days following a major shock. Being highly attuned to the seismic risks of living in this part of the country, households in the Wellington region are receptive to this message, as illustrated by the recent surge in demand for 200-litre rainwater tanks.         

The opportunity

The Wellington region has a great opportunity to take the learnings from the Canterbury earthquakes and to invest in improvements over time that will enable infrastructure systems to better withstand major shocks and avoid the exponentially higher costs from a sudden major system failure. A resilient region is one that will remain attractive as place to live and for businesses to operate and invest in, contributing to economic growth. Key to the region’s success in this regard will be its ability to work together.

The water supply resilience project involves developing an investment plan for client councils’ 2018 Long Term Plans to ensure our water supply networks meet agreed levels of service after a major earthquake.

Better Business Case approach

We’re using Treasury’s Better Business Case approach on the water supply resilience project. The first step of the process is the strategic business case. The strategic case describes the agreed problem, explains the case for change and the benefits of investing for that change.

We’re now working through the second stage of the process - the programme business case. In this stage, we’ll develop and seek agreement on levels of service councils will invest to achieve, and the investment criteria against which options will be measured. We’ll consider a wide range of options and what mix of options will best deliver our desired outcomes. This roadmap sets out the main steps and timeline for our programme business case.

Levels of service

We’re working with our client councils to develop and agree levels of service that are affordable and achievable within an agreed timeframe. Levels of service for water supply after a major earthquake include a number of factors:

  • how much water could or should be provided each day to residents and how far they might have to walk to get it 
  • target times to reinstate a reticulated supply to residents and to businesses 
  • how to supply critical users such as hospitals, medical centres and emergency management facilities, and how much to supply them 
  • the target time to fully recover from an event, that is, to return to normal operating conditions

Stakeholder updates

We're working with a range of stakeholders to ensure their perspectives are taken into account as we develop the programme business case.

We'll engage with stakeholders through meetings and regular updates. See below for copies of our newsletter updates.