WATER SHARING PLAN FOR THE GREATER METROPOLITAN REGION UNREGULATED RIVER WATER SOURCES 2011 - REG 34
Environmental flow releases in the Hawkesbury and Lower Nepean Rivers Water Source
WATER SHARING PLAN FOR THE GREATER METROPOLITAN REGION UNREGULATED RIVER WATER SOURCES 2011 - REG 34
Environmental flow releases in the Hawkesbury and Lower Nepean Rivers Water Source
34 Environmental flow releases in the Hawkesbury and Lower Nepean Rivers Water
Source
(1) Subject to subclause (8), a daily release of water must be made
from Menangle Weir in the Menangle Weir Management Zone in the Hawkesbury and
Lower Nepean River Water Source which is equal to the volume of water released
in the prior 24-hour period from Pheasants Nest Weir under clause 32 (7) plus
the volume of water released in the prior 24-hour period from Broughtons Pass
Weir under clause 32 (8), multiplied by:
(a) 1 when the total daily inflows to
Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are greater than the 80 th
percentile of the total daily inflows to those dams,
(b) 0.9 when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams, or
Note : The factor 0.9 in the
paragraph above accounts for the current best estimate of the natural
transmission loss that occurs between Pheasants Nest Weir and Broughtons Pass
Weir and the Menangle Weir Management Zone flow reference point when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams.
(c) 0.8 when the total daily inflows
to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less
than the 95 th percentile of the total daily inflows to those dams.
Note : The
factor 0.8 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Menangle Weir Management Zone flow reference
point when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are equal to or less than the 95 th percentile of the total daily
inflows to those dams.
(2) Subject to subclause (8), a daily release of water
must be made from Camden Weir in the Camden Weir Management Zone in the
Hawkesbury and Lower Nepean River Water Source which is equal to the volume of
water released in the prior 24-hour period from Pheasants Nest Weir under
clause 32 (7), plus the volume of water released in the prior 24-hour period
from Broughtons Pass Weir under clause 32 (8), multiplied by:
(a) 1 when the
total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are
greater than the 80 th percentile of the total daily inflows to those dams,
(b) 0.878 when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam
and Nepean Dam are equal to or less than the 80 th percentile and greater than
the 95 th percentile of the total daily inflows to those dams, or
Note : The
factor 0.878 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Camden Weir Management Zone flow reference point
when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are equal to or less than the 80 th percentile and greater than the
95 th percentile of the total daily inflows to those dams.
(c) 0.761 when the
total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are
equal to or less than the 95 th percentile of the total daily inflows to those
dams.
Note : The factor 0.761 in the paragraph above accounts for the current
best estimate of the natural transmission loss that occurs between Pheasants
Nest Weir and Broughtons Pass Weir and the Camden Weir Management Zone flow
reference point when the total daily inflows to Cataract Dam, Cordeaux Dam,
Avon Dam and Nepean Dam are equal to or less than the 95 th percentile of the
total daily inflows to those dams.
(3) Subject to subclause (8), a daily
release of water must be made from Sharpes Weir in the Sharpes Weir Management
Zone in the Hawkesbury and Lower Nepean River Water Source which is equal to
the volume of water released in the prior 24-hour period from Pheasants Nest
Weir under clause 32 (7), plus the volume of water released in the prior
24-hour period from Broughtons Pass Weir under clause 32 (8), multiplied by:
(a) 1 when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are greater than the 80 th percentile of the total daily inflows to
those dams,
(b) 0.871 when the total daily inflows to Cataract Dam, Cordeaux
Dam, Avon Dam and Nepean Dam are equal to or less than the 80 th percentile
and greater than the 95 th percentile of the total daily inflows to those
dams, or
Note : The factor 0.871 in the paragraph above accounts for the
current best estimate of the natural transmission loss that occurs between
Pheasants Nest Weir and Broughtons Pass Weir and the Sharpes Weir Management
Zone flow reference point when the total daily inflows to Cataract Dam,
Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less than the 80 th
percentile and greater than the 95 th percentile of the total daily inflows to
those dams.
(c) 0.748 when the total daily inflows to Cataract Dam, Cordeaux
Dam, Avon Dam and Nepean Dam are equal to or less than the 95 th percentile of
the total daily inflows to those dams.
Note : The factor 0.748 in the
paragraph above accounts for the current best estimate of the natural
transmission loss that occurs between Pheasants Nest Weir and Broughtons Pass
Weir and the Sharpes Weir Management Zone flow reference point when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 95 th percentile of the total daily inflows to those dams.
(4) Subject to subclause (8), a daily release of water must be made from
Cobbity Weir in the Cobbity Weir Management Zone in the Hawkesbury and Lower
Nepean River Water Source which is equal to the volume of water released in
the prior 24-hour period from Pheasants Nest Weir under clause 32 (7), plus
the volume of water released in the prior 24-hour period from Broughtons Pass
Weir under clause 32 (8), multiplied by:
(a) 1 when the total daily inflows to
Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are greater than the 80 th
percentile of the total daily inflows to those dams,
(b) 0.863 when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams, or
Note : The factor 0.863 in the
paragraph above accounts for the current best estimate of the natural
transmission loss that occurs between Pheasants Nest Weir and Broughtons Pass
Weir and the Cobbity Weir Management Zone flow reference point when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams.
(c) 0.734 when the total daily inflows
to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less
than the 95 th percentile of the total daily inflows to those dams.
Note : The
factor 0.734 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Cobbity Weir Management Zone flow reference point
when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are equal to or less than the 95 th percentile of the total daily
inflows to those dams.
(5) Subject to subclause (8), a daily release of water
must be made from Mount Hunter Rivulet Weir in the Mount Hunter Rivulet Weir
Management Zone in the Hawkesbury and Lower Nepean River Water Source which is
equal to the volume of water released in the prior 24-hour period from
Pheasants Nest Weir under clause 32 (7), plus the volume of water released in
the prior 24-hour period from Broughtons Pass Weir under clause 32 (8),
multiplied by:
(a) 1 when the total daily inflows to Cataract Dam, Cordeaux
Dam, Avon Dam and Nepean Dam are greater than the 80 th percentile of the
total daily inflows to those dams,
(b) 0.858 when the total daily inflows to
Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less than
the 80 th percentile and greater than the 95 th percentile of the total daily
inflows to those dams, or
Note : The factor 0.858 in the paragraph above
accounts for the current best estimate of the natural transmission loss that
occurs between Pheasants Nest Weir and Broughtons Pass Weir and the Mount
Hunter Rivulet Weir Management Zone flow reference point when the total daily
inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or
less than the 80 th percentile and greater than the 95 th percentile of the
total daily inflows to those dams.
(c) 0.726 when the total daily inflows to
Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less than
the 95 th percentile of the total daily inflows to those dams.
Note : The
factor 0.726 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Mount Hunter Rivulet Weir Management Zone flow
reference point when the total daily inflows to Cataract Dam, Cordeaux Dam,
Avon Dam and Nepean Dam are equal to or less than the 95 th percentile of the
total daily inflows to those dams.
(6) Subject to subclause (8), a daily
release of water must be made from Brownlow Hill Weir in the Brownlow Hill
Weir Management Zone in the Hawkesbury and Lower Nepean River Water Source
which is equal to the volume of water released in the prior 24-hour period
from Pheasants Nest Weir under clause 32 (7), plus the volume of water
released in the prior 24-hour period from Broughtons Pass Weir under clause 32
(8), multiplied by:
(a) 1 when the total daily inflows to Cataract Dam,
Cordeaux Dam, Avon Dam and Nepean Dam are greater than the 80 th percentile of
the total daily inflows to those dams,
(b) 0.856 when the total daily inflows
to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less
than the 80 th percentile and greater than the 95 th percentile of the total
daily inflows to those dams, or
Note : The factor 0.856 in the paragraph above
accounts for the current best estimate of the natural transmission loss that
occurs between Pheasants Nest Weir and Broughtons Pass Weir and the Brownlow
Hill Weir Management Zone flow reference point when the total daily inflows to
Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less than
the 80 th percentile and greater than the 95 th percentile of the total daily
inflows to those dams.
(c) 0.721 when the total daily inflows to Cataract
Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less than the 95 th
percentile of the total daily inflows to those dams.
Note : The factor 0.721
in the paragraph above accounts for the current best estimate of the natural
transmission loss that occurs between Pheasants Nest Weir and Broughtons Pass
Weir and the Brownlow Hill Weir Management Zone flow reference point when the
total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are
equal to or less than the 95 th percentile of the total daily inflows to those
dams.
(7) Subject to subclause (8), a daily release of water must be made
from Theresa Park Weir in the Theresa Park Weir Management Zone in the
Hawkesbury and Lower Nepean River Water Source which is equal to the volume of
water released in the prior 24-hour period from Pheasants Nest Weir under
clause 32 (7), plus the volume of water released in the prior 24-hour period
from Broughtons Pass Weir under clause 32 (8), multiplied by:
(a) 1 when the
total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are
greater than the 80 th percentile of the total daily inflows to those dams,
(b) 0.837 when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam
and Nepean Dam are equal to or less than the 80 th percentile and greater than
the 95 th percentile of the total daily inflows to those dams, or
Note : The
factor 0.837 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Theresa Park Weir Management Zone flow reference
point when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are equal to or less than the 80 th percentile and greater than the
95 th percentile of the total daily inflows to those dams.
(c) 0.687 when the
total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are
equal to or less than the 95 th percentile of the total daily inflows to those
dams.
Note : The factor 0.687 in the paragraph above accounts for the current
best estimate of the natural transmission loss that occurs between Pheasants
Nest Weir and Broughtons Pass Weir and the Theresa Park Weir Management Zone
flow reference point when the total daily inflows to Cataract Dam, Cordeaux
Dam, Avon Dam and Nepean Dam are equal to or less than the 95 th percentile of
the total daily inflows to those dams.
(8) Daily releases of water under
subclauses (1)-(7) are not required to be made for the respective weir when:
(a) the release requirements cannot be met due to an emergency situation at
that weir or an upstream weir and the holder of the water supply work approval
notifies the Minister in writing within 7 days of becoming aware of the
emergency,
(b) the Minister is satisfied that the release requirements cannot
be met due to water supply work capacity constraints or necessary maintenance,
refurbishment or modification work, at that weir or an upstream weir, that has
the potential to temporarily affect the flow rate or behaviour of water for a
period of more than 24 hours and has granted permission in writing,
(c) the
Minister requires an alternate release to be made due to an emergency
situation or a maintenance activity at that weir or an upstream weir and has
notified this in writing,
(d) the stage of the weir is less than the stage
necessary to deliver the required environmental release at that weir or an
upstream weir over the 24-hour period, or
(e) the respective weir is spilling
at a rate that equals or exceeds the respective release requirement specified
in subclause (1)-(7), or
(f) from Years 1 to 5 of this Plan, the release
requirements cannot reasonably be met despite the best endeavours of the
holder of the water supply work approval to meet them.
(9) Subject to
subclause (10), a daily release of water must be made from Wallacia Weir in
the Wallacia Weir Management Zone in the Hawkesbury and Lower Nepean River
Water Source which is equal to the volume of water released in the prior
24-hour period from Pheasants Nest Weir under clause 32 (7), plus the volume
of water released in the prior 24-hour period from Broughtons Pass Weir under
clause 32 (8), multiplied by:
(a) 1 when the total daily inflows to Cataract
Dam, Cordeaux Dam, Avon Dam and Nepean Dam are greater than the 80 th
percentile of the total daily inflows to those dams,
(b) 0.810 when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams, or
Note : The factor 0.810 in the
paragraph above accounts for the current best estimate of the natural
transmission loss that occurs between Pheasants Nest Weir and Broughtons Pass
Weir and the Wallacia Weir Management Zone flow reference point when the total
daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal
to or less than the 80 th percentile and greater than the 95 th percentile of
the total daily inflows to those dams.
(c) 0.640 when the total daily inflows
to Cataract Dam, Cordeaux Dam, Avon Dam and Nepean Dam are equal to or less
than the 95 th percentile of the total daily inflows to those dams.
Note : The
factor 0.640 in the paragraph above accounts for the current best estimate of
the natural transmission loss that occurs between Pheasants Nest Weir and
Broughtons Pass Weir and the Wallacia Weir Management Zone flow reference
point when the total daily inflows to Cataract Dam, Cordeaux Dam, Avon Dam and
Nepean Dam are equal to or less than the 95 th percentile of the total daily
inflows to those dams.
(10) Daily releases of water under subclause (9) are
not required to be made when:
(a) the release requirements cannot be met due
to an emergency situation at that weir or an upstream weir and the holder of
the water supply work approval notifies the Minister in writing within 7 days
of becoming aware of the emergency,
(b) the Minister is satisfied that the
release requirements cannot be met due to water supply work capacity
constraints or necessary maintenance, refurbishment or modification work, at
that weir or an upstream weir, that has the potential to temporarily affect
the flow rate or behaviour of water for a period of more than 24 hours and has
granted permission in writing,
(c) the Minister requires an alternate release
to be made due to an emergency situation or a maintenance activity at that
weir or an upstream weir and has notified this in writing,
(d) the stage of
the weir is less than the stage necessary to deliver the required
environmental release at that weir or an upstream weir over the 24-hour
period, or
(e) Wallacia Weir is spilling at a rate that equals or exceeds the
applicable release requirement specified in subclause (9), or
(f) from Years
1 to 5 of this Plan, the release requirements cannot reasonably be met despite
the best endeavours of the holder of the water supply work approval to meet
them.
(11) If the Minister determines that any of the release requirements
specified in this clause cannot reasonably be met despite the best endeavours
of the holder of the water supply work approval to meet them, the Minister is
to conduct a review by the end of Year 5 of this Plan of the factors that
prevent the release requirements from being met and the ways in which those
factors can be addressed, for the purposes of determining how those those
factors should be addressed, whether the system operation rules specified in
this clause should be amended and/or whether the water supply works specified
in this clause require modification in order to pass the required releases.
