Hydro Risk Curves

Current Status

New Zealand  and South Island Hydro Risk Meter

The graphs below compare New Zealand and South Island controlled storage to the relevant Hydro Risk Curves.

As at 21 October, New Zealand and South Island controlled storage is below average.  The risk meter for the New Zealand and the South Island is set to Normal.

Find out more about hydro risk curves
Latest New Zealand Hydro Risk and South Island Hydro Risk Curves [ pdf 59.7 KB ]
Hydro Risk Curve Update Log [ pdf 679.48 KB ]
Hydro Risk Curve Input Assumptions [ pdf 898.38 KB ] (Effective from 12 October 2018)
Hydro Risk Curve Data for 2018 [ xlsx 33.77 KB ] (Effective from 12 October 2018) 
HRC Demand forecast update note - January 2018 [ pdf 707.58 KB ]
Simulated Storage Trajectories [ pdf 167.03 KB ] (Updated 25 September 2018)
Simulated Storage Trajectories: Assumptions [ pdf 680.11 KB ] (Updated 25 September 2018)

HRC assumptions

Thermal fuel limitations

Transpower is seeking feedback on our proposed treatment of potential limitation of thermal fuel availability in the Hydro Risk Curve (HRC) assumptions.

In late-2017 we received information from Genesis Energy regarding a potential limitation of thermal fuel availability. This a prompted a review of the treatment of thermal fuel, and specifically potential thermal fuel limitations, in the Hydro Risk Curves Input Assumptions.  We have finished this review and have proposed a modified process for the treatment of thermal fuels in the HRC assumptions, described in the consultation document below.

As such we are seeking feedback on the treatment of this information with respect to the HRC assumptions, as required by  clause 6.3 of the Security of Supply Forecasting and Information Policy [ pdf 425.37 KB ]. We ask you provide feedback no later than 5:00pm Friday 6 July.

Consultation document for Thermal Fuel Limitations in the Hydro Risk Curves [ pdf 546.71 KB ]

Previous Consultation

HRC Assumption thermal fuel limitations [ pdf 796.65 KB ]
Thermal fuel limitation consultation – Update 6 March 2018
Thermal Fuel Limitation Submissions 
Bryan Leyland [ pdf 19.44 KB ] Contact Energy [ pdf 22.43 KB ] Cumulus [ pdf 397.32 KB ]
Genesis [ pdf 280.06 KB ] Mercury [ pdf 40.06 KB ] Meridian [ pdf 205.78 KB ]
MEUG [ pdf 100.46 KB ] Murray Ellis [ pdf 13.81 KB ] Nova [ pdf 184.5 KB ]
Shell [ pdf 92.75 KB ] Trust Power [ pdf 471.72 KB ] Unison [ pdf 276.25 KB ]
Vocus [ pdf 49.67 KB ]    

Tekapo Contingent Storage

220 GWh of controlled storage at Lake Tekapo is classified as contingent storage from 1 October to 31 March. This contingent storage only becomes available once reported controlled storage falls to the 4% risk curve. The Hydro Risk Curves (HRCs) are being adjusted to exclude this contingent storage at Lake Tekapo to align with the SoSFIP. As a result of this adjustment, HRCs from January to March as well as in October will decrease, while HRCs in other months will increase. For example, the 10% HRC will increase by a maximum of 213 GWh in September and decrease by 144 GWh in March. It is important to note that reported storage will be 220 GWh lower from 1 October to 31 March – this effect is illustrated below. The reported nominal full values have also been adjusted accordingly.

The change to reported storage from 1 October to 31 March offsets the decrease in the HRCs from January to March (and October), and as such the net impact is to effectively increase the HRCs for all months. That is, while the HRCs have decreased, reported storage will be decreased by a greater amount.

We appreciate that one consequence of this change is to increase the complexity of the Hydro Risk Curves, and as such we are readily available to discuss with anyone should they require further clarification or information.  Please contact Bennet Tucker if you require further information using bennet.tucker@transpower.co.nz.