WATER SHARING PLAN FOR THE GREATER METROPOLITAN REGION UNREGULATED RIVER WATER SOURCES 2011 - REG 32 Environmental flow releases in the Upper Nepean and Upstream Warragamba Water Source

WATER SHARING PLAN FOR THE GREATER METROPOLITAN REGION UNREGULATED RIVER WATER SOURCES 2011 - REG 32

32 Environmental flow releases in the Upper Nepean and Upstream Warragamba Water Source

(1) Subject to subclause (12), in addition to the daily release requirement specified in clause 33 (1), a daily release of water must be made from Wingecarribee Reservoir into the Wingecarribee River equal to 3 ML/day.

(2) The volume of water released under subclause (1) must be measured at the Wingecarribee River at Sheepwash Bridge gauge (212275) or at such alternative flow reference points or by such methods as determined in writing by the Minister.

(3) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Avon Dam in accordance with the following:

(a) subject to subclause (12), when the daily inflows into Lake Avon are less than or equal to the 80 th percentile daily inflow, a daily release of water which is equal to the daily inflows must be made,

Note : 6.8 ML/day corresponds to the estimated 80 th percentile daily inflow.

(b) subject to subclause (12), when the daily inflows into Lake Avon are greater than the 80 th percentile daily inflow, a daily release of water which is equal to the 80 th percentile daily flow plus 20% of the daily inflows above the 80 th percentile daily inflow must be made,

(c) for the purposes of paragraphs (a) and (b):

(i) daily inflows into Lake Avon must be calculated by a method approved in writing by the Minister either:

(A) taking into account flows measured at the Avon River at Summit Tank gauge (2122111) and the Flying Fox No. 3 Creek at Fire Road gauge (2122112), or such alternate flow reference points as determined in writing by the Minister, and an estimate of any other tributary inflows, or

(B) taking into account changes in water storage levels, net evaporation, other losses and outflows, and

(ii) the volume of water released must be measured in a manner approved in writing by the Minister.

(4) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Cataract Dam in accordance with the following:

(a) subject to subclause (12), when the daily inflows into Lake Cataract are less than or equal to the 80 th percentile daily inflow, a daily release of water which is equal to the daily inflows must be made,

Note : 14.5 ML/day corresponds to the estimated 80 th percentile daily inflow.

(b) subject to subclause (12), when the daily inflows into Lake Cataract are greater than the 80 th percentile daily inflow, a daily release of water which is equal to the 80 th percentile daily inflow plus 20% of the inflow volume above the 80 th percentile daily inflow must be made,

(c) for the purposes of paragraphs (a) and (b):

(i) daily inflows into Lake Cataract must be calculated by a method approved in writing by the Minister either:

(A) taking into account flows measured at the Loddon River at Bulli Appin Road gauge (2122322) and the Cataract River at Corrimal No. 1 gauge (2122323), or such alternative flow reference points as determined in writing by the Minister, and an estimate of any other tributary inflows, or

(B) taking into account changes in water storage levels, net evaporation, other losses and outflows, and

(ii) the volume of water released must be measured in a manner approved in writing by the Minister.

(5) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Nepean Dam in accordance with the following:

(a) subject to subclause (12), when the daily inflows into Lake Nepean are less than or equal to the 80 th percentile daily inflow, a daily release of water which is equal to the daily inflows must be made,

Note : 20.1 ML/day corresponds to the estimated 80 th percentile daily inflow.

(b) subject to subclause (12), when the daily inflows into Lake Nepean are greater than the 80 th percentile daily inflow, a daily release of water which is equal to the 80 th percentile daily inflow plus 20% of the inflow volume above the 80 th percentile daily inflow must be made,

(c) for the purposes of paragraphs (a) and (b):

(i) daily inflows into Lake Nepean must be calculated by a method approved in writing by the Minister either:

(A) taking into account flows measured at the Nepean River at Nepean Dam gauge (2122051) and the Burke River at Nepean Dam gauge (2122052), or such alternative flow reference points as determined in writing by the Minister, and an estimate of any other tributary inflows, or

(B) taking into account changes in water storage levels, net evaporation, other losses and outflows, and

(ii) the volume of water released must be measured in a manner approved in writing by the Minister.

(6) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Cordeaux Dam in accordance with the following:

(a) subject to subclause (12), when the daily inflows into Lake Cordeaux are less than or equal to the 80 th percentile daily inflow, a daily release of water which is equal to the daily inflows must be made,

Note : 4.5 ML/day corresponds to the estimated 80 th percentile daily inflow.

(b) subject to subclause (12), when the daily inflows into Lake Cordeaux are greater than the 80 th percentile daily inflow, a daily release of water which is equal to the 80 th percentile daily inflow plus 20% of the inflow volume above the 80 th percentile daily inflow must be made,

(c) for the purposes of paragraphs (a) and (b):

(i) daily inflows into Lake Cordeaux must be calculated by a method approved in writing by the Minister either:

(A) taking into account flows measured at the Goondarrin Creek at Kemira "D" Cast gauge (2122201) and the Sandy Creek at Cordeaux River gauge (2122205), or such alternative flow reference points as determined in writing by the Minister, and an estimate of any other tributary inflows, or

(B) taking into account changes in water storage levels, net evaporation, other losses and outflows, and

(ii) the volume of water released must be measured in a manner approved in writing by the Minister.

(7) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Pheasants Nest Weir in accordance with the following:

(a) subject to subclause (12), a daily release must be made from Pheasants Nest Weir which is equal to:

(i) the volume of water released that day from Avon Dam, Nepean Dam and Cordeaux Dam under subclauses (3), (5) and (6) respectively and clauses 37 (5) and 38 (4), plus

(ii) the volume of water that is equal to:

(A) daily inflows to the catchment between Pheasants Nest Weir and Avon Dam, Nepean Dam and Cordeaux Dam, when the daily inflow is less than or equal to the 80 th percentile daily inflow, or

Note : 4.5 ML/day corresponds to the estimated 80 th percentile daily inflow to the catchment between Pheasants Nest Weir and Avon Dam, Nepean Dam and Cordeaux Dam.

(B) the 80 th percentile daily inflow into the catchment between Pheasants Nest Weir and Avon Dam, Nepean Dam and Cordeaux Dam plus 20% of the inflow volume above the 80 th percentile daily inflow, when the daily inflows are greater than the 80 th percentile daily inflow,

(b) for the purposes of paragraph (a):

(i) travel time, transmission losses and other relevant factors may be taken into account as set out in methods approved in writing by the Minister, for the purpose of calculating the volume to be released from Pheasants Nest Weir under paragraph (a) (i) based on releases made from Avon Dam, Nepean Dam and Cordeaux Dam that day under subclauses (3), (5) and (6) and clauses 37 (5) and 38 (4),

(ii) the inflow volume to the catchment between Pheasants Nest Weir and Avon Dam, Nepean Dam and Cordeaux Dam must be measured by Water NSW in a manner approved in writing by the Minister, and

(iii) the volume of water released must be measured in a manner approved in writing by the Minister.

(8) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Broughtons Pass Weir in accordance with the following:

(a) subject to subclause (12), a daily release must be made from Broughtons Pass Weir which is equal to:

(i) the releases made from Cataract Dam that day under subclause (4) and clauses 37 (5) and 38 (4), plus

(ii) the volume of water that is equal to:

(A) daily inflows to the catchment between Broughtons Pass Weir and Cataract Dam, when the daily inflow is less than or equal to the 80 th percentile daily inflow, or

Note : 4.4 ML/day corresponds to the estimated 80 th percentile daily inflow to the catchment between Broughtons Pass Weir and Cataract Dam.

(B) the 80 th percentile daily inflow into the catchment between Broughtons Pass Weir and Cataract Dam plus 20% of the inflow volume above the 80 th percentile daily inflow, when the daily inflows are greater than the 80 th percentile daily inflow,

(b) for the purposes of paragraph (a):

(i) travel time, transmission losses and other relevant factors may be taken into account as set out in methods approved in writing by the Minister, for the purpose of calculating the volume to be released from Broughtons Pass Weir under paragraph (a) (i) based on releases made from Cataract Dam that day under subclause (4) and clauses 37 (5) and 38 (4),

(ii) the inflow volume to the catchment between Broughtons Pass Weir and Cataract Dam shall be calculated by Water NSW by a method approved in writing by the Minister taking into account flows measured at the Cataract River at Broughtons Pass Notch gauge (212230), or such alternative flow reference points as determined in writing by the Minister, and

(iii) the volume of water released must be measured in a manner approved in writing by the Minister.

(9) Subject to subclause (12), in the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Lake Lyell in accordance with the following:

(a) subject to paragraphs (d) and (e), when the daily inflows into Lake Lyell are less than or equal to 13.6 ML/day, a daily release of water which is equal to the daily inflows must be made,

(b) subject to paragraphs (d) and (e), when the daily inflows into Lake Lyell are greater than 13.6 ML/day, a daily release of water which is equal to 13.6 ML/day plus 25% of the daily inflow volume above 13.6 ML/day must be made,

(c) subject to paragraph (e), if in any water year a flow of 800 ML/day or more has not occurred for a period of at least one hour at the Coxs River at Lithgow gauge (212011), an annual channel maintenance flow release must be made which is equal to the lesser of:

(i) a release rate of 800 ML/day, or

(ii) the maximum release rate obtainable from the outlet valves when fully open,

for a period of two hours continuously from Lake Lyell in accordance with procedures and a timeframe determined in writing by the Minister,

(d) releases under paragraphs (a) and (b) are not required to be made when an annual channel maintenance flow release is being made in accordance with paragraph (c),

(e) releases under paragraphs (a), (b) and (c) are not required to be made when the total active storage in Lake Lyell, Lake Wallace and Thompsons Creek Reservoir is less than 50,000 megalitres,

(f) when the total active storage in Lake Lyell, Lake Wallace and Thompsons Creek Reservoir has been less than 50,000 megalitres continuously for less than six months, a daily release of water must be made which is equal to the lesser of daily inflows to Lake Lyell and 9.0 ML/day, and

(g) when the total active storage in Lake Lyell, Lake Wallace and Thompsons Creek Reservoir has been less than 50,000 megalitres continuously for six months or more, a daily release of water must be made which is equal to the lesser of daily inflows to Lake Lyell and 5.0 ML/day.

(10) For the purposes of subclause (9):

(a) the volume of water released must be calculated by a method approved in writing by the Minister taking into account flows measured at the Coxs River at Lithgow flow gauge (212011), or such alternative flow reference points as determined in writing by the Minister, and

(b) daily inflows into Lake Lyell must be calculated by a method approved in writing by the Minister either:

(i) taking into account flows measured at the Coxs River at upstream of Lake Lyell gauge (212058) and Farmers Creek at Mount Walker gauge (212042), or such alternative flow reference points as determined in writing by the Minister, or

(ii) taking into account changes in water storage levels, net evaporation, other losses and outflows.

(11) Subject to subclause (12), in the Upper Nepean and Upstream Warragamba Water Source a daily release of water must be made from Lake Wallace which is equal to 0.7 ML/day. This release requirement may also be met by water released below the Lake Wallace Dam wall from the Wallerawang Power Station cooling towers.

(12) Daily releases of water under subclauses (1)-(11) are not required to be made for the respective storage when:

(a) the release requirements cannot be met due to an emergency situation 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 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 and has notified this in writing, or

(d) the respective storage is spilling at a rate that equals or exceeds the respective release requirement specified in subclauses (1)-(11), provided that in the case of Wingecarribee Reservoir, the storage must be spilling at a rate that equals or exceeds the respective release requirements specified in subclause 32 (1) and clause 33 (1).

(13) In the Upper Nepean and Upstream Warragamba Water Source, daily releases of water must be made from Thompsons Creek Reservoir in accordance with the following:

(a) between 1 September and 30 April inclusive, a daily release of water must be made which is equal to 0.8 ML/day,

(b) between 1 May and 31 August inclusive, a daily release of water must be made which is equal to 0.3 ML/day,

(c) for the purposes of paragraphs (a) and (b), the volume of water released must be calculated by a method approved in writing by the Minister taking into account flows measured at the V Notch Weirs at Thompsons Creek Reservoir, or such alternative flow reference points as determined by the Minister,

(d) daily releases of water under this subclause are not required to be made when:

(i) the release requirements cannot be met due to an emergency situation and the holder of the water supply work approval notifies the Minister in writing within 7 days of becoming aware of the emergency,

(ii) 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 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,

(iii) the Minister requires an alternate release to be made due to an emergency situation or a maintenance activity and has notified this in writing, or

(iv) Thompsons Creek Reservoir is spilling at a rate that equals or exceeds the respective release requirement under paragraph (a) or (b).

(14) Subject to subclause (15), the following rules apply to releases by weirs located in the Maldon Weir Management Zone in the Upper Nepean and Upstream Warragamba Water Source:

(a) a daily release of water must be made from Maldon Weir in the Maldon Weir Management Zone which is equal to the volume of water released in the prior 24-hour period from Pheasants Nest Weir under subclause (7), multiplied by:

(i) 1 when the total daily inflows to Cordeaux Dam, Avon Dam and Nepean Dam are greater than the 80 th percentile of the total daily inflows to those dams,

(ii) 0.9 when the total daily inflows to 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 Douglas Park Weir respectively when the total daily inflows to 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.

(iii) 0.8 when the total daily inflows to 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 Maldon Weir and Douglas Park Weir respectively when the total daily inflows to 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.

(15) Daily releases of water under subclause (14) are not required to be made when:

(a) the release requirements cannot be met due to an emergency situation 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 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 and has notified this in writing,

(d) the stage of the weir is less than the stage necessary to deliver the required environmental release over the 24-hour period,

(e) Maldon Weir is spilling at a rate that equals or exceeds the applicable release requirement specified in subclause (14), 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.

(16) If 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.