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).
Lake Levels
Island Inflows and Storage
The charts below show storage over the last 13 weeks and rolling 7 day inflows for the last year in North and South Islands.
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Contingent Storage
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.