4228 NEW ZEALAND GAZETTE No. 168

3. Lakes management—The parties recognise three
   separate operating ranges of levels for each of the Lakes
   within which Meridian Energy Limited may operate, being
   Main, High and Low, as set out in clauses 4, 5 and 6 of this
   notice.

4. The Main Operating Ranges—(1) The Main Operating
   Ranges, within which Meridian Energy Limited shall
   endeavour to maintain continuous variation, are:

(a) for Lake Manapouri, levels from 176.8m to 178.6m;
and

(b) for Lake Te Anau, levels from 201.5m to 202.7m.

(2) Meridian Energy Limited shall, for each of the lakes,
aim to achieve annual mean levels within the applicable
Main Operating Ranges as specified in this notice.\n
5. The High Operating Ranges—(1) Meridian Energy
Limited shall use its best endeavours to:

(a) not exceed the maximum durations; and

(b) achieve the specified ratio in relation to the
ranges of level set out in subclause (2) of this clause,
where the actual interval (in days) between the
Lake moving below a particular range of level
and returning to within that range of level is divided
by the actual duration (in days) that the Lake was
originally within that range of level.

(2) Subject to subclause (3) of this clause, the High Operating
Ranges are:

(a) for Lake Manapouri, above 178.6m, in accordance
with the following maximum durations, minimum
intervals, and specified ratios for the ranges of level
set out:

(b) for Lake Te Anau, above 202.7m, in accordance
with the following maximum durations, minimum
intervals, and specified ratios for the ranges of levels
set out:

(3) Where the ratio derived from dividing the interval
between the lake level moving below a particular range
of level and returning to that range of level by the duration
that the lake was in that range of level immediately prior to
the interval:

(a) results in a ratio greater than or equal to the
specified ratio, then the guidelines are deemed to be
complied with.

(b) results in a ratio less than the specified ratio, then
subject to subclause (4) of this clause, the interval
occurring after a particular duration shall be added
to that duration along with the duration occurring
after that interval, in order to determine the duration
for which the specified ratio must be achieved.

(4) The period of duration within any range of level,
including accumulations as provided for in paragraph (b) of
subclause (3) of this clause, shall not exceed the relevant
maximum duration.

(5) The parties record that:

(a) High Operating Range guidelines were reviewed in
2001 and are based on the mean of the three extreme
events during the period of natural and synthetic
record from 1933 to 2000.

(b) the 1988 flood was excluded from this review
because of its damaging high levels and extended
duration. Extreme natural floods have occurred
historically, e.g. 1988: Lake Te Anau 205.41m, Lake
Manapouri 182.15m. It is accepted that guideline
breaches may occur on rare occasions despite the
best endeavours of the power station operator.

6. The Low Operating Ranges—(1) Subject to subclause
   (2) of this clause, the Low Operating Ranges are:

(a) for Lake Manapouri levels from 175.86m to 176.8m,
with an absolute minimum level of 175.86:

(b) for Lake Te Anau from 200.86m to 201.5m, with an
absolute minimum level of 200.86m:

(2) For the purposes of the Low Operating Ranges outlined
in subclause (1) of this clause, Meridian Energy Limited
shall use its best endeavours to:

(a) not exceed the maximum durations for the individual
ranges of levels specified;

(b) avoid lake levels below 201.1m for Lake Te Anau
and below 176.2m for Lake Manapouri during
the equinoxial periods (March, April, October and
November);

(c) not exceed, in any continuous period of 365 days,
twice the maximum duration specified for any
particular range of level; and

(d) ensure the rates of drawdown do not exceed the
natural rates of drawdown averaged over four
days, being 0.05m per day for Lake Manapouri and
0.03m per day for Lake Te Anau.

(3) The parties record that:

(a) in the period of natural record, the level of Lake
Manapouri has been below the absolute minimum
level of 175.86m; and

(b) these guidelines are based on the mean of three
extreme events during the period of natural record
and may result in low ranges of level being
experienced more often than would have occurred
naturally.