New Zealand’s hydro lake storage remained well below average at the beginning of August.
On August 4th, hydro lake storage was 1912.7 GWh, which is 79% of average levels, down from 86% on July 14th. This figure is lower than storage at the same date in 2003, 2004 and 2005.
Water flowing into the storage lakes was above average in the weeks to the 14th and 21st of July, but then plunged to below average figures. During the week to August 4th, inflows stood at only 384 GWh, which is 94% of average.
National electricity demand has remained consistently above last year’s figures since the week ending 17th June. During much of July, this seems to have been met by increasing hydro generation from North Island sources, with South Island hydro generation being at or slightly below last year’s figures except for peaks on 4 days. Electricity generated from other sources (geothermal, oil, wind and gas) in the North Island has been at or below last year’s figures during July.
With major load centres located in the North Island it is often assumed that the Cook Strait cable normally carries electricity from the southern generators to meet this demand. However, energy transfers from the North Island to the South Island exceeded south-to-north transfers on 23 days during July, to meet increased southern demand and preserve the southern hydro lake storage.
The North Island hydro storage is normally replenished during winter rains whilst the South Island hydro lakes generally fill with springtime snowmelt. With national storage currently at 79% of average, this year’s melt is becoming crucial.
[Compiled from data supplied by M-co.]