Dry Winter Planning

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Preparation work currently underway Treatment of Contingent Storage 1% Threshold Reporting and Actions  

Since February, hydro storage has been declining due to low inflows in the South Island. We are currently experiencing a dry winter.

Transpower, as system operator, has specific duties to monitor, analyse and, if required, manage dry winter situations. We also oversee the administration of policies which govern how New Zealand security of supply is managed. 

Storage in the South Island crossed the 1% Hydro Risk Curves (HRCs) on 22 May 2017, followed by storage crossing the New Zealand 1% HRC on 27 May 2017.  Storage is sitting below the 1% HRC in the South Island and below the 1% HRC in New Zealand.  Given the time of year and long range weather forecast, we don’t expect storage to increase in the short to medium term.

We are relatively late in the year in terms of winter energy risk and it is likely there is sufficient water in the storage lakes to make it through to spring inflows.  In this context, the likelihood of requiring any emergency response, such as an official conservation campaign, remains low. 

We are preparing for all possible outcomes and are taking steps to ensure we are prepared to undertake an emergency response if required.

The following is an update on the dry year planning work we have underway. 

The page is updated weekly and was last updated on 21 July 2017.

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Preparation work currently underway

Various assessments and studies are planned as described below:

  • Grid Assessments to maximise water conservation: this includes a review of planned outages with specific focus on outages constraining HVDC south transfer, constraining hydro generation on or constraining thermal generation off.  
  • We are assessing whether any temporary grid reconfigurations (TGRs) may improve security of supply.
  • We have implemented a variable line rating for the Livingstone-Naseby 1 and Naseby-Roxburgh 1 circuits.
  • We are also assessing the benefit special protection schemes, system inter trips or additional reserve arrangements.
  • We welcome industry feedback or suggestions for ways in which to maximise water conservation.

Treatment of Contingent Storage

On 8 June 2017, we received a request from Meridian Energy to consider an urgent change to our Security of Supply and Forecasting Information Policy (SoSFIP) to include contingent storage in the calculation of the hydro risk curves (HRCs). The current policy is to exclude contingent storage from the calculation of the HRCs.

On 21 June 2017, Meridian advised it would no longer seek consent for Pukaki contingent storage to be accessed at a lower risk level.  Consequently, any urgent change to the SoSFIP would apply only to Lake Hawea contingent storage being included in the HRC calculations (67 GWh of storage that becomes accessible at the 4% HRC).

Latest Update

Transpower, in its role as System Operator, has determined it will not submit a variation to the Electricity Authority to change the treatment of contingent storage.

Click for full details on the Decision on Treatment of Contingent Storage [ pdf 207.87 KB ]
Click for further information on Contingent storage

1% Threshold Reporting and Actions

We introduced additional reporting and monitoring activities when the 1% hydro risk curve was reached on 22 May 2017. See links below for more information.

Latest Update
click for Daily Security of Supply Update page
click for Hydro Risk Curves

Other Relevant Information

South Power Transfer Challenges Overview 2017 [ pdf 663.97 KB ]
Summary of 14.06.17 Dry Year Teleconference with industry [ pdf 114.66 KB ]
Summary of 06.07.17 Dry Year Teleconference with industry [ pdf 335.72 KB ]

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