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Published 29/07/2020

Planning for a sustainable water supply

The Wellington Region’s potable water supply and storage capacity is sufficient to adequately supply our current needs, but at Wellington Water we take a long-term approach to working with our client councils to plan for a growing population and changing environment. 

The region’s water supply is primarily river-based. For more than 10 months of a typical year, these rivers (and the aquifer fed by Te Awa Kairangi) supply more than we need. In summer, river flows decrease and water demand increases, so supply is then supplemented by water from the two storage lakes at Te Marua.

One of the issues we have to consider in terms of planning for sustainability of supply is that water consumption in our region is comparatively high relative to our population. To delay the expense, disruption and carbon cost of constructing new bulk storage, as a community we need to look at ways of managing our water consumption.

Currently, we do this on a seasonal basis to manage immediate demand on the storage lakes when rainfall is low. Each summer, we introduce alternate day watering restrictions across the region (Upper Hutt chooses to have these in place year-round). When we have a drier summer than normal we have occasionally stepped up restrictions to a sprinkler ban. Only once in the past 25 years have we had to institute full outdoor use restrictions across the region, when one lake was out of service for a resilience upgrade.

Longer-term, managing demand requires a smarter water network, providing more detailed information on how and where water is being used. Greater Wellington Regional Council asked Wellington Water to report on the options and potential benefits of installing meters within the potable water network.

Metering can help manage demand in two main ways. Firstly, it enables high-quality monitoring of flow levels within the network, meaning significant leaks can be identified, located and repaired faster and more cost-effectively. Secondly, it can provide greater awareness of local usage levels, informing consumer decision-making in relation to consumption.

Ultimately, decisions around investment in drinking water capacity and consumption management will be made by councils, as representatives of the community. Wellington Water’s role is providing detailed technical advice to support their decision-making processes. We have advised that increased water metering across the region provides substantial network management benefits, and would be a key tool in implementing our shareholder councils’ expressed preference for a strategy which includes responsible demand management alongside increasing supply.

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