Hydro Lake Storage Improves

Hydro lake storage improved during September, with strong inflows at the beginning and end of a month during which energy was transferred from the North Island to the South Island on most days.

On September 1st, national hydro lake storage stood at 73% of average, or 1653 GWh. However, as the month progressed, this value crept slowly upward hovering at or below 80% of average until September 22nd when it began rising following strong inflows.

Lake inflows were below average on 15 days, with storage receiving a boost between September 2nd and 7th and between the 20th and 28th when above average amounts of water flowed into the storage lakes. Despite this, national hydro storage was consistently lower than at the same time last year until the 26th, when it reached 90% of average at 2038 Gigawatt hours (GWh).

By the end of the month storage was still below average (91%) at 2064 GWh, a figure 3% higher than at the same time last year, but still at or slightly below storage figures for 2004 and 2003.

The erratic inflows reflect inconsistent snowmelt and changeable weather as brief cold snaps were experienced in both islands. Anecdotal evidence of water levels improving in shallow wells in inland Canterbury while the deeper wells showed little change during September tends to confirm the dry trend.

Once again, electricity managers protected southern lake levels by ensuring that north-to-south electricity transfers exceeded south-to-north transfers until the 26th and on the 29th. Electricity was transferred in greater amounts from the South Island between the 26th and 29th to utilise a dramatic increase in lake inflows, which briefly peaked at 207% of normal on the 26th.

The inflow trend for October is now crucial in eliminating the 9% deficit in storage to take us back to average levels before the commencement of the dry summer which is expected in some lake catchments.

[Compiled from data supplied by M-co.]

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