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For security of supply purposes, hydro storage is divided into two categories; controlled and contingent storage. Generators can use controlled storage at any time, but contingent storage may only be used during defined periods of shortage or risk of shortage. During sustained dry periods, controlled and contingent storage are important indicators of overall supply risks. Storage is expressed in gigawatt-hours – GWh (a measure of the energy that can be produced using the water).
Total available storage for New Zealand is below average for this time of the year.
The chart below compares storage at each hydro lake for the most recent Tuesday, the Tuesday last week, and the historic average for this time of year. Percentages shown on the chart are the % of full for each lake.
The charts below show storage over the last 13 weeks and rolling 7 day inflows for the last year in North and South Islands.
- Over the last week available storage in the North Island has increased and the South Island has decreased.
- Inflows over the last 4 weeks in the North Island is above average and in the South Island has been below average.
|North Island||South Island|
Contingent storage is stored hydro that is only made available for generation at specific times to mitigate the risk of shortage. Current available contingent storage is shown on the following graph.
For more information on contingent storage and the conditions of its use, refer to the documents below.
|Contingent Storage additional information [ pdf 167.95 KB ]|
|HRC101 - Contingent Storage [ pdf 372.62 KB ]|