text:
Sydney Catchment Authority's
Operating Licence
Final Report
Prepared for IPART by
Review of the Performance Criteria in
Sydney Catchment Authority's
Operating Licence
Final Report
Prepared for IPART by
Research Paper RP21
July 2003
This is copyright. The Copyright Act 1968 permits fair dealing for
study, research, news reporting, criticism and review. Selected
passages, table or diagrams may be reproduced for such purposes
provided acknowledgement of the source is included.
QVB POST OFFICE NSW 1230 . The views expressed her are those of the author alone and do not reflect the position of IPART or the New South Wales Government.This report was commissioned by the Independent Pricing and Regulatory Tribunal. Sydney NSW 2000 Ph 02 9290 8400 Fax 02 9290 2061 www. The author of this report is SKM Inquiries regarding this paper should be directed to Michael Sedwell 02 9290 8487 Independent Pricing and Regulatory Tribunal of New South Wales Level 2.au ALL CORRESPONDENCE TO: PO BOX Q290.ipart.gov. 44 Market Street.nsw.
............3......................................40 6.............. Water Supply System Yield and Performance Criteria... 21 Performance Criteria Objectives.................1 The SCA Supply System.................1............................... 5 2...........3.......................................... Security of Supply Performance Criteria Elsewhere..............39 6......1 2.............. 21 3... 37 6.............................3................ 34 Summary.................................................. 1 Study objectives................6 Option 6: Maintaining Equal Supply Assurance Across the Entire System 40 6...........................................3 Water Management Licence Requirements .................18 3.............................1............... 3 2........1...........................2 3..........2 5...........................................................................2 4.... 10 Performance measures used for water supply systems.. 25 4................................ 2 Layout of this report.............1 3.....3 5.............1 Option 1: Status Quo........ Options for Adopting Appropriate Security of Supply Criteria for Sydney.......................26 Relevance to Sydney's water supply system................ 37 6....... 23 Compliance with Performance Criteria......3 Option 3: With Distinction of Security Specifications for Different Types of Use..................10 Yield estimation......................................Contents Executive summary 1...............................4 Objectives of Supply Authorities within Australia and Overseas................3 1....... SCA's Current Operating Licence and Performance Criteria Objectives........ 1 Methodology .............4 What is appropriate for SCA's Operating Licence?...DOC FINAL PAGE i ...........................................................................2 2...1 5...5 Option 5: System Yield Only.........3..... Introduction ................................ 23 3...................................................................................1 4................................................................................... 38 6.......................................1 The context of performance criteria ...............................2 Interactions with Other Relevant Regulatory and Legislative Instruments.........................24 4..2 2.......................................3....................40 6.4 Option 4: Stating the System Yield ...................................................................... 29 5............2 Determining compliance................................ 34 6......39 6............. 11 2........................3 Performance Criteria .................... 5 2..2 Option 2: A Set of Primary and Secondary Criteria ......... 29 How Should These Objectives be Achieved?...1 Performance Criteria used by the Bulk Water Suppliers.1 3..........2 Non-resource constrained areas .3.............................................. 7 Operational Considerations .... 41 WC02486:FINAL REPORT JUNE 2003..... 27 5............................................3 Appropriate Combinations of Criteria......... 29 Objectives Relevant to Sydney's system...25 Resource constrained areas.................................................3............................... 37 6..................1...........................................................4 Background to the review of the performance criteria..............3.................................................24 Yield estimation............. 9 Supply Constraints......... Objectives Underlying Performance Criteria ........1.1 Desirable Attributes of Performance Criteria........3 2...................................3........................ 25 4......................39 6....2 1.....................1 1................... 1 1.............................................................................
... 43 7....... Conclusions and Recommendations ............................1 What is Appropriate as the Buffer Storage Level ....................................... 47 8................................................2 Example......... 47 Recommendations ......... Expressing the Criteria .............................2 Conclusions ................................................DOC FINAL PAGE ii ......................................... 44 7..... 43 7..........................1 Proposed Form and Content.......................................4........................................................................................1 8......3 Information Recommended for Removal From Schedule 2 of the Operating Licence......................................41 7..................... 46 8............. 47 WC02486:FINAL REPORT JUNE 2003.......6....................
Doc Pat Little Dr Paul Pretto Independent Pricing and Regulatory Tribunal Review of the Performance Criteria in Sydney Catchment Authority's Operating Licence Final Report R06 WC02486 WC02486:FINAL REPORT JUNE 2003. Quantity R04 1 Michael Sedwell (by e-mail) R05 4 copies + email 1 copy e -mail Michael Sedwell.Document History and Status Rev. (by e-mail) 2 copies (mail) Michael Sedwell Printed: Last Saved: File Name: Author: Project Manager: Name of Organisation: Name of Project: 3 July. Simone Greenaway (SCA). Date Reviewed By Approved By R01 26/05/03 Paul Pretto Paul Pretto R04 03/06/03 R05 06/06/03 David Barnes. Erlanger Paul Pretto R06 (Final) 30/06/03 Pat Little Peter Revision Details Paul Pretto Paul Pretto Paul Pretto Distribution of copies: Copy No. 2003 2 July.DOC FINAL PAGE iii . 2003 R06 Name of Document: Document Version: Project Number: Issued To Michael Sedwell I:\Wcms\Wc02486\REP03_04.07\Final\R06_IPART_Prl.
Environment Protection Authority of NSW
Department of Infrastructure, Planning and Natural
Independent Pricing and Regulatory Tribunal of NSW
Metropolitan Water District of Southern California
State Environmental Planning Policy
Sydney Catchment Authority
Sydney Water Corporation
Water Filtration Plant
Hawkesbury Nepean River Management Forum
The body established to make recommendations to the NSW government on
environmental flow provisions for inclusion in the Sydney Catchment Authority's
Water Management licence.
Pump mark
The "pump mark" is the level of overall system storage at which pumping commences
from the Shoalhaven system in order to increase water availability to Sydney.
Currently the pump mark is set at 60 % of overall storage.
95th Percentile Flow
The 95th percentile flow is the flow which occurs or is exceeded 95% of the time. It is
a relatively low flow.
Translucent flow releases
Releases whereby a percentage of inflows to a dam must be released. This involves
passing a fixed percentage of the actual inflow to the dam and aims to mimic natural
flow patterns.
Transparent flow releases
Releases from water storages that are matched to inflows to the storage.
PAGE iv
Executive Summary
Background to the Review of the Performance Criteria
The Independent Pricing and Regulatory Tribunal of New South Wales (IPART) is the
Operating Licence Regulator for the Sydney Catchment Authority (SCA). A number
of issues were identified relating to the Performance Criteria contained in Schedule 2
of the Operating Licence during the Mid Term Operating Licence Review and the
2001/2002 Operational Audit. Those issues related to:
The applicability of one of the criteria, the "security" criterion which, strictly, was
found to be non-compliant for the purposes of the audit, although by an
insignificant margin;
The difficulty of understanding and interpreting the criteria;
Framing of the criteria in terms of the forecast rather than the actual demand of
Sydney Water Corporation; and
Assessment of compliance based on probabilistic modelling which means there is
inherent uncertainty in assessing performance.
Study Objectives
The study objectives are to review the expression and form of the performance criteria
and assess whether they are:
Clear, concise and appropriate; and
Whether alternative expressions and/or forms of the criteria are more suitable.
The review of the criteria was undertaken with particular reference to:
Criteria adopted by comparable bulk suppliers;
The appropriateness of the criteria in the context of SCA's operating environment;
Comments by operating licence auditors and, in particular, the 2001 audit;
Comments made in submissions to the Mid-term licence review and by
participants at the associated Tribunal workshop; and
Ease of application and clarity.
The methodology used for this study involved a survey of the major Australian (and
some overseas) urban bulk water suppliers to ascertain current practice for
performance criteria and the objectives underlying those criteria. This was followed
by consultation with key stakeholders to the SCA water supply system to determine
the range of objectives that they would wish the performance criteria to satisfy. The
stakeholders consulted were:
Sydney Catchment Authority (SCA);
Sydney Water Corporation (SWC);
Environment Protection Authority of NSW (EPA);
PAGE v
NSW Ministry for Energy and Utilities;
The Hawkesbury-Nepean River Management Forum and its Independent Expert
Shoalhaven Water and Wingecarribee Shire Council;
NSW Health; and
The NSW Department of Infrastructure, Planning and Natural Resources
The outcomes of the survey of water supply authorities and discussions with
stakeholders were then used as a basis for reviewing and assessing the performance
Practice elsewhere and performance criteria objectives
The survey of other water authorities revealed that practice varied according to
whether or not the water resource was constrained in being able to provide continuous
supply to system demands without restriction. In areas where the water resource was
abundant, and the reliability perceived to be 100 percent, the approach using explicit
performance criteria (other than 100% reliability) was not used. In resource
constrained areas, similar to Sydney, a similar approach to that of Sydney's was
adopted using water restrictions to protect a buffer storage by applying water
restrictions in time of drought. The performance criteria used generally dealt with the
acceptable frequency, severity and duration of restrictions.
Discussions with the key stakeholders provided clarity regarding the performance
criteria's major objectives, which are summarised as :
The Primary Objective is to ensure the system does not run out of water;
The secondary, supporting, objectives are to ensure that the frequency, duration
and severity of water restrictions that may be anticipated in ensuring the primary
objective is achieved are acceptable to the community being served.
The discussions indicated that the revised environmental flow requirements (currently
being addressed by the Hawkesbury-Nepean Management Forum) would be contained
in the Water Management Licence issued by DIPNR, and hence would not need to be
explicitly addressed by the Performance Criteria. The concept of stating the
sustainable yield of the system as part of the Performance Criteria was suggested in
order to provide a focus for demand management initiatives, and promote the
sustainable yield of the resource. There was also agreement that the anticipated
demand reductions for various levels of water restrictions, as currently stated in
Schedule 2 of the Operating Licence, were overly optimistic and should be reviewed.
Current modelling practice by the SCA does not allow for the demand fluctuations
induced by climate variability (eg that in dry years the demand would be greater than
average) and it was considered that this practice by the SCA should be revised.
Sydney's system may be regarded as supply limited – for example, the area designated
for the Welcome Reef Dam, which previously had been the preferred next major
augmentation scheme, has been proclaimed as a nature reserve. There is a clear
community expectation that the water supply should be managed within current
resources. This sentiment should be reflected in the Operating Licence by not
PAGE vi
and sufficient pressure. The model uses the projected average water demands. too severely. or for excessively long periods. on average. The probability of the system storage levels falling to the buffer storage level shall not exceed 1 occasion in 1. to all parts of the system. based on the preferences of the community. measurable. shall include a contingency plan. The following is an example of the suggested form and content of the criteria. together with the Drought Response Plan: (a) Have the primary objective of ensuring that the water supply system should not run out of water . A minimum operating storage equivalent to x months of total restricted demand (or y % of storage) shall be maintained as a buffer to assure supply continuity. 2) Performance Criteria (a) Supply Continuity. (b) Achieve this objective without imposing water restrictions too frequently.000 years (for example).DOC FINAL PAGE vii . and 3) A statement regarding the system yield. (b) Water restrictions frequency. achievable.that is that the supply can continue to meet the restricted demand requirements with water of acceptable quality. and (d) Are intended to promote the sustainable use of the available water resources. there is a degree of modelling uncertainty. (c) Describe the standard of service to be provided to customers in terms of the frequency. Restrictions will not need to be applied. triggered by impingement of the storage buffer.including criteria expressed in a way that drive the SCA to increase the available supply in order to comply. The performance criteria are used in a computer model of the water supply system that can estimate the likelihood of certain events occurring. A Drought Response Plan. WC02486:FINAL REPORT JUNE 2003. drawn up in collaboration with Sydney Water Corporation. adjusted to reflect climatic conditions. controllable and relevant. more often than once every ten years (for example). Appropriate Performance Criteria Revised criteria should be clear. severity and duration of water restrictions which may be anticipated. Because of the uncertainty around future climatic conditions. to ensure that basic supplies can continue to be met for an indefinite period. The proposed form for the criteria is that they comprise: 1) An introduction including a statement of the Performance Criteria Objectives 2) The Performance Criteria. which is allowed for in the performance criteria. and other factors. "Catchment Infrastructure Works Performance Criteria 1) Introduction and Objectives of the Performance Criteria These performance criteria.
DOC FINAL PAGE viii ." Recommendations The following recommendations are made: q That the Performance Criteria as drafted for the example provided above be taken forward for further consideration as part of the End of Term Review of the SCA's Operating Licence. by the system modelling). Restrictions for continuous periods exceeding 24 months (for example) shall not be required. WC02486:FINAL REPORT JUNE 2003. (d) Water restrictions severity: Water restrictions requiring a demand reduction of 50% (for example. That the modelling procedure used to assess performance of the system against the Performance Criteria specified in Schedule 2 must be consistent with appropriate and acceptable industry practice. to provide an average yield of 600 GL/year (or such other figure as may be determined. q That the implications of the proposed Performance Criteria be investigated to ensure they are achievable within the context of current policy. q That the table of water restriction levels.(c) Water restrictions duration. The system shall be operated. more than once in 200 years (for example). no be longer included in the SCA's Operating Licence. and To actively work with other Authorities/bodies to ensure that appropriate water demand management. or whatever demand reduction is anticipated by the highest level of restrictions) shall not be required more often.1): − − − − To ensure that the system is operated consistent with maintaining the yield stated in Schedule 2. showing anticipated savings and average occurrence probability. but be transferred to an alternative. on average. and water recycling and reuse strategies are in place. for example it should incorporate the impact of climate variability on the system demands. In addition to operating the supply system consistent with providing the yield as specified in Schedule 2. on average. from time to time. be omitted from Schedule 2 of the Operating Licence and carried over to the SCA's Drought Response Plan. than once in 200 years (for example). q That the modelling procedure used to assess performance of the system against these criteria must be consistent with acceptable industry practice. the current pattern of demands and restriction rules stated in the Drought Response Plan. q That the water demand projections. for example as stated by the NSW Premier in March 2003 (Premier of New South Wales. 2003). currently included with the Performance Criteria. based on the above criteria. to meet the requirements of the Water Management Licence. relevant and publicly accessible document. q That consideration be given as to whether the Operating Licence should be amended to clearly reflect the following obligations on the SCA (potentially included as sub-clauses under the current Clause 8. specifically for the release of environmental and riparian flows.
DOC FINAL PAGE ix .q That the anticipated demand reductions following the implementation of water restrictions should be reviewed in the light of the introduction of water conservation measures and other factors. WC02486:FINAL REPORT JUNE 2003.
DOC FINAL PAGE x .WC02486:FINAL REPORT JUNE 2003.
000 months). it makes recommendations regarding the most suitable expression and form that these criteria should take. The review should consider whether adopting extreme monthly event criterion is deliverable. to an acceptable degree of accuracy by the model process. 2001/02 Audit q Review the applicability of the "security" criterion as part of the mid-term review of the Operating Licence. The current study was designed to provide further information to enable the criteria to be reconsidered during the end of term review. q The criteria and assessment of compliance is framed in terms of the Catchment Authority's capacity to meet Sydney Water Corporation's forecast demand. for conformity to the performance requirements contained within their Operating Licence.DOC FINAL PAGE 1 . which means there is inherent uncertainty in assessing performance. In addition. The following issues were noted in relation to the performance criteria during the 2001/02 Operational Audit and during a Mid-term Operating Licence Review. The SCA's Operating Licence was issued in April 2000 under the Sydney Water Catchment Management Act 1998. rather than Sydney Water Corporation's actual demand. the review should consider whether the level and likelihood set by the criterion is appropriate (the level of the operating storage should not fall below 5 % more often than one month in 100.1 Background to the review of the performance criteria The Independent Pricing and Regulatory Tribunal of New South Wales (IPART) is the Operating Licence Regulator for the Sydney Catchment Authority (SCA). through Operational Audits. Introduction 1.2 Study objectives The study objective were to review the expression and form of the performance criteria and to assess whether they are: WC02486:FINAL REPORT JUNE 2003.1. q The assessment of compliance with the criteria is based on probabilistic modelling. Mid-term Review q The criteria are expressed in an unnecessarily complicated way that makes them difficult to interpret. requiring that a Mid-term Review be undertaken in about January 2002 to determine whether the Licence is fulfilling its objectives. Specifically. The Mid-term Review recommended that there was "insufficient information to recommend changes to the criteria at this time" but that "these criteria be reconsidered at the end of term review". q If the "security" criterion is deemed technically feasible. 1. the operations of the Sydney Catchment Authority are reviewed by IPART.
The review of the criteria was undertaken with particular reference to: q Criteria adopted by comparable bulk suppliers. the 2001 audit. q q Comments made in submissions to the Mid-term licence review and by participants at the associated Tribunal workshop. in particular.q Clear. q The appropriateness of the criteria in the context of SCA's operating environment.3 Methodology The methodology used for this study is shown schematically in Figure 1-1. n Figure 1-1 Project Methodology Project Inception Determine Practice Elsewhere Performance Criteria Objectives Performance criteria and objectives for other large bulk suppliers Stakeholder contact to document objectives Criteria assessment Assess criteria against objectives Stakeholder consultation Reporting Draft report Presentation to IPART Final report WC02486:FINAL REPORT JUNE 2003. concise and appropriate. 1. and q Whether alternative expressions and/or forms of the criteria are more suitable. and Ease of application and clarity. q Comments by operating licence auditors and.DOC FINAL PAGE 2 .
§ Ministry for Energy and Utilities. § Shoalhaven Water and Wingecarribee Shire Council. A list of the organisations contacted can be found in Section 4. clarity of interpretation and ease and effectiveness of application. 1. Section 2 briefly describes the physical water supply infrastructure concerned to provide the context for the performance criteria. The assessment also considered the appropriateness of the criteria in relation to practical assessment capabilities. § The Environment Protection Authority of New South Wales. the background rationale for adopting those criteria. as far as possible.DOC FINAL PAGE 3 . § Sydney Catchment Authority. and § DIPNR. in particular regarding the objectives that should underlie the performance criteria.The main tasks involved the following: q Determination of Practice Elsewhere: Major urban bulk water suppliers throughout Australia were requested to provide information regarding the performance criteria that they used.4 Layout of this report This report has adopted the following layout and logic: q q Section 1 introduces the subject and provides background information. WC02486:FINAL REPORT JUNE 2003. § The Hawkesbury-Nepean River Management Forum and its Independent Expert Panel. The following organisations were consulted through interviews with members of the project team or for review of documents: § Sydney Water Corporation. Assessment of the Performance Criteria: An assessment of the SCA's existing performance criteria was undertaken. q q Determination of Performance Criteria Objectives: The key stakeholder organisations associated with Sydney's water supply and with management of its water supply catchments were also consulted to obtain their input to the review. what were the specific objectives in relation to supply security that needed to be satisfied and how did these relate to the criteria against which performance in achieving them is measured? Two overseas organisations that manage large urban water supply systems with similar characteristics to Sydney's were also requested to provide similar information. § NSW Health. considering both the criteria employed by the other large urban bulk water suppliers consulted and the relevant objectives identified in the preceding tasks. This assessment involved consideration of the appropriateness of the existing criteria and whether any alternative forms of criteria could be used to better satisfy the objectives. These organisations were also asked to provide. In particular.
and the means of addressing the various issues raised by the key stakeholders. q Section 4 discusses the results of a survey of the performance criteria used by other water supply authorities both within Australia and overseas.DOC FINAL PAGE 4 . It also assesses the relative merits of the options and recommends. WC02486:FINAL REPORT JUNE 2003. and the regulatory framework within which SCA operates. the key criteria for consideration in relation to the SCA's supply system.q Section 3 presents the current Performance Criteria and the objectives underlying those criteria as perceived by SCA. q Section 6 identifies the various options for adopting appropriate performance criteria for Sydney in terms of the desirable attributes of those criteria. q Section 8 summarises the principal conclusions and recommendations from this investigation. q Section 7 addresses the appropriate form and expression to be adopted to define the key criteria. in conceptual terms. particularly concerning the objectives they see the performance criteria should satisfy. and presents an example of the performance criteria for consideration. q Section 5 presents the feedback received from discussions held with the key stakeholders involved with Sydney's water supply.
comprises six main components: q The Prospect Reservoir System. as well as to local government areas outside the Sydney distribution system. the system supplies. and notes some of the relevant performance constraints on the system. owned and operated (under agreement with SWC) plants. through a network of pipelines and canals. Bulk water is supplied from the SCA's system of 18 major dams and 2 diversion weirs. q The Warragamba Dam and Warragamba Pipeline System. the Upper Nepean Dams and the Woronora Dam. Water Supply System Yield and Performance Criteria This section of the report briefly describes the key characteristics of the bulk water supply system for Sydney. The SCA system does not include the water filtration plants . It also describes how the system yield of water supply systems.SWC owns and operates five of these. such as the Sydney system.2. which effectively define the points of demand on the SCA bulk water supply system. pipelines or the Upper Canal.000 million litres of bulk water per year for over 4 million people. as operated by the Sydney Catchment Authority (SCA). to 11 water filtration plants. one is owned and operated by the Wingecarribee Shire Council and the remaining one by the Shoalhaven City Council. q The Shoalhaven System. Overall. 2.DOC FINAL PAGE 5 . q The Woronora Dam System. over 600. four are privately built. The supply system. on average. Small volumes of raw water are also supplied to a small number of minor customers directly from the storages. The supply system incorporates infrastructure including the Shoalhaven System. It concludes by providing a short review of the performance criteria that can be applied to water supply systems in general. WC02486:FINAL REPORT JUNE 2003. shown schematically in Figure 2-1. is determined and provides important definitions for the terms commonly used. the Warragamba and Blue Mountains Dams. q The Upper Nepean Dams and Upper Canal System. The system is operated to supply demands drawn through the water filtration plants.1 The SCA Supply System The SCA supplies bulk water to the Sydney Water Corporation (SWC) for treatment and supply to the Sydney metropolitan area. and q The Blue Mountains System.
2.3) Cascades WFP Greaves Creek Dam Penrith/Lower BlueMts Supply Zone Greaves Creek WFP Fish River Water Katoomba/Leura Supply Zone Sydney Metropolitan Supply Zone Prospect Reservoir Orchard Hills WFP Medlow Dam Prospect WFP Riparian Blackheath/Mt Victoria Supply Zone Macarthur Supply Zone Warragamba WFP Hawkesbury-Nepean River Warragamba Dam Warragamba Supply Zone Sutherland Supply Zone Upper Canal Broughtons Pass Weir Woronora WFP Macarthur WFP Pheasants Nest Weir Helensburgh Supply Zone Nepean Tunnel Woronora Dam Cataract River Wollondilly River Woronora River Nepean River Picton/Bargo Supply Zone Cordeaux River Cataract Dam Avon River Cordeaux Dam Nepean WFP Upper Cord. Canal.DOC FINAL PAGE 6 Proposed Treated Water Pipeline . Dam No1 Nepean Dam Legend Illawarra WFP Wingecarribee Reservoir Glenquarry Cut Control Structure Wingecarribee River BOO WFP SWC WFP Other WFP Bowral Supply Zone Dam or Reservoir Fitzroy Falls Reservoir Pumping Station Kangaroo Pipeline Control structure Supply Zone Kangaroo Valley Supply Zone Bendeela Pondage River Channel Raw Water Pipeline. Dam No2 Avon Dam Illawarra Supply Zone Nepean-Avon Tunnel Upper Cord.n Figure 2-1 Schematic Outline of SCA's Bulk Water Supply System (source: SCA) Cascade Dams (1. etc Shoalhaven River Treated Water Pipeline Tallowa Dam To Nowra WC02486:FINAL REPORT JUNE 2003.
SWC draws water from the Hawkesbury-Nepean River at North Richmond for supply to customers in that region.1 Water Management Licence Require ments In addition to providing water for urban use. No environmental flow releases are required when the works are spilling naturally. currently specifies provisional environmental flow releases required for each of its water management works.9 ML/day 3 ML/day 1.7 ML/day 1. The SCA is not required to make specific bulk supplies for North Richmond. This is also the case for agricultural demands drawn from the river below the SCA's storages. Flows from local catchments and environmental releases from the SCA's storages sustain supply to that plant. and the glossary) while inflows are equal to or greater than those flows. which is issued and regulated by DIPNR.DOC FINAL PAGE 7 .5 ML/day 1. These release requirements are being reviewed through the Hawkesbury-Nepean River Management Forum and it is envisaged that a more rigorous environmental flow regime. and provides a supplement to the Blue Mountains supply sources. consistent with sustaining the long term health of the Hawkesbury–Nepean system. these agricultural demands and the demand at the North Richmond WFP are not explicitly included as part of the demand for bulk water upon which the yield of the SCA's supply system is based. As such.1. and passing the natural inflow when this is less than the 95th percentile flow. n Table 2-1 Environmental flow release requirements specified in SCA's Water Management Licence – 95th percenti le flows Water Management Works Warragamba Dam Cataract Dam Nepean Dam Pheasants Nest Weir Broughtons Pass Weir Cordeaux Dam Wingecarribee Dam Avon Dam 95th Percentile Flows 33. This connection has provided increased flexibility to source the best quality water.3 ML/day 4. In addition. This water is treated at the North Richmond Water Filtration Plant.8 ML/day 2 1 Notes: WC02486:FINAL REPORT JUNE 2003.4 ML/day 10. as required.In the early 1960's the Blue Mountain System was connected to the Fish River water supply scheme. will be recommended to Government. during dry periods or whilst maintenance work is carried out.3 ML/day 1. The releases currently specified correspond to passing the 95th percentile flows (shown and explained in Table 2-1. 2. SCA's Water Management Licence.
a flow of only 1. A release of 90 ML/day or natural inflow (whichever is less) must also be maintained from Tallowa Dam until environmental flow provisions recommended by the Shoalhaven-Illawarra Water Management Committee have been endorsed in a Water Management Plan. Where natural inflow to Tallowa Dam is between 90 ML/day and 180 ML/day (inclusive). With the existing dam infrastructure. In addition. a smaller release rate). in this case the daily flow equalled or exceeded on at least 95 days out of 100. In addition annual high flow releases (800 ML/day for at least 3 days per year) from January 2003 are required. the SCA must release Shoalhaven City Council's supply requirements (up to a maximum of 90 ML/day) in addition to the environmental flow releases. The Water Management Licence also has rules governing releases and transfers between the Shoalhaven and Hawkesbury-Nepean catchments and from Wingecarribee Reservoir to the Wollondilly River and to the Nepean Reservoir (Schedule 3 of the licence). and the SCA must ensure a flow equivalent to five thirds of the inflow of Wildes Meadow Creek into Fitzroy Falls Reservoir is maintained over the Fitzroy Falls. This amount was designed to mimic the pre-dam inflow volume and is subject to review during the course of the licence. 2) Currently. The SCA must release a minimum flow of 10 ML/day from Warragamba Dam in addition to the environmental flow releases. Releases from Woronora Dam are required under an adaptive environmental flow management regime. WC02486:FINAL REPORT JUNE 2003. nor cater for. the Water Management Licence specifies riparian release requirements. A riparian flow release equivalent to 1 ML/day must also be made from Wingecarribee Dam. When inflow to the Dam is less than 40 ML/day.8 ML/day cannot be released from Avon Dam. The Hawkesbury-Nepean River Management Forum is currently reviewing the environmental flow provisions and is investigating options that could potentially reduce the yield for consumptive purposes below the current estimate of 600 GL/year.DOC FINAL PAGE 8 . the SCA must ensure that a minimum flow of 50 ML/day is maintained over Penrith Weir. which occurs or is exceeded 95% of the time. It is a relatively low fl ow.1) The 95th percentile flow is the flow. the minimum possible downstream release is 25 ML/day (original construction of the outlet infrastructure in the 1920s did not envisage. and translucent releases (for which a specified percentage of the incoming flow to the water storage must be released) when inflow is greater than 5 ML/day but less than 30 ML/day. This comprises transparent flow releases (for which the entire flow entering the water storage must be released) where inflow is less than or equal to 5 ML/day. due to the physical configuration of the outlet works.
the Illawarra and to Wingecarribee supply systems. q Parts of the Blue Mountains system cannot be supplied from the main part of the SCA system. Water can be transferred from Nepean Reservoir to Avon Reservoir through the Nepean-Avon Tunnel. and q in Nepean Reservoir to ensure there is sufficient head to enable transfers to Avon Reservoir through the Nepean-Avon Tunnel. or likelihood of water restrictions.2 Operational Considerations Generally the SCA supply system can be operated so that the points of demand (ie.2. This plant supplies the towns of Picton. Although water is not typically released for supply to Prospect WFP from the Nepean and Avon Reservoirs due to the need to maintain water: q in Avon Reservoir to supply the Illawarra. However. such releases from Nepean Reservoir are important in balancing overall storage levels during periods of drought. The Shoalhaven system is a combined pumped storage hydropower and water supply facility. WC02486:FINAL REPORT JUNE 2003. This ensures that consumers in different supply areas experience equal water supply assurance. the water filtration plants) can be supplied with water from several different sources. Raw water can be released from Wingecarribee Reservoir to flow into the Warragamba Reservoir. There are however some exceptions to this as follows: q The Raw water from Nepean Reservoir is the only supply source for the Nepean Water Filtration Plant (WFP) through a pumped rising main. Oakdale. and this key link in the system is used to ensure supply can be maintained to the Illawarra Supply Zone. during periods of drought. Transfers from the Shoalhaven system into Wingecarribee Reservoir are important during periods of drought to augment supplies to Sydney. with diversions from the Nepean and Shoalhaven catchments. Supply via this route would not normally be provided due to the expected high level of losses (including river diversions) between Wingecarribee Reservoir and Warragamba Reservoir and to the need to transfer water into the Nepean and Avon reservoirs to maintain supplies to the Illawarra.1. q The Illawarra WFP has its own supply by both a gravity pipeline and a pumped rising main from the Avon Reservoir. Thirlmere. Current operating rules dictate that pumping from the Shoalhaven system into Wingecarribee Reservoir would start when the total SCA system storage level falls to 60% (known as the "pump mark").DOC FINAL PAGE 9 . Buxton and Green Hills. transfers of water from Wingecarribee Reservoir to Warragamba Reservoir are made based on the balance of requirements in the different parts of the supply system.
in contrast to accessing further supply sources and building additional dams. WC02486:FINAL REPORT JUNE 2003. social and economic costs. 2.2 Yield estimation The capacity of a water supply system to supply water is assessed by estimating the system's yield. Yield can be defined as the annual volume of water that can be supplied. In September 2001. SCA). and that the Nadgigomar Nature Reserve would be established on land previously purchased for future construction of the dam (Premier of New South Wales. and not the demand that may be placed on the system. on the Shoalhaven River.DOC FINAL PAGE 10 . had been identified as the preferred option for next major augmentation of the SCA supply system. both financial and environmental.2.1. the New South Wales Minister for the Environment announced that plans for construction of this dam would be deferred indefinitely. and water recycling and reuse. in the long term. on average. In March 2003 the Premier issued a news release which confirmed that plans for the dam had been scrapped. Although there are potentially other supply side options available for investigation that could increase yield without full scale augmentation. by the system subject to: q The system configuration and operational rules. These announcements have increased the emphasis placed on management of the demand for water. which would have significant associated environmental.3 Supply Constraints In previous planning. q The seasonal pattern of water supply from the system and any associated impacts of climatic variability. The SCA system is therefore. q The variability of water inflows (typically streamflows) to the system and of any other climatic factors affecting the system. be better than the performance criteria requirements and there will be some excess capacity for the system to supply demand. to some extent. and q The level of service (water resource security performance) criteria adopted for the system. the Welcome Reef Dam. new supply source schemes are envisaged (Pers Comm. Where the demand is less than the yield. The yield therefore defines a characteristic of the supply system (its ability to supply water under a specified set of operating conditions). the system performance will. however. supply limited. no large. Full scale augmentation options would involve significant costs. 2003).
restrictions will be triggered earlier for higher average demands. By comparing the estimated yield with forecast levels of demand on the system. and water restrictions not applied. This figure can be used to illustrate the fundamental concepts underlying the main types of drought security performance criteria. there are six basic types of system performance measures related to representing water resource security for the operation and planning of urban supply systems. WC02486:FINAL REPORT JUNE 2003. or to decrease the demand through demand management in order to ensure that the system demands can continue to be satisfied within the constraints of the required performance criteria. or to supply the existing demand without violating the level of service. (b) The trigger may vary on a monthly basis. especially in areas which experience most of their rainfall at a particular time of the year. 2. the system performance will only just satisfy the criteria or will fail against some or all of the criteria. This flags the need to either investigate options for increasing the yield. an assessment of any potential lack of supply capacity in the system can be made. In general. and (c) The trigger will vary according to the predicted average annual demand . depending on whether the total storage volume is below or above (respectively) the drought restriction trigger shown.3 Performance measures used for water supply systems The typical range of measures used for water supply systems are discussed below. provide the basis for the performance criteria adopted for water supply systems. This indicates that the system has no capacity to supply any additional demand.DOC FINAL PAGE 11 .that is. Figure 2-2 provides a simple illustration of the typical behaviour over time for the volume of water stored in the storage(s) of a (hypothetical) urban water supply system. It should be noted that Figure 2-2 has been simplified and that there are at least three respects in which the line representing the boundary between "no restrictions" and "restrictions" may be more complex in practice: (a) The trigger line(s) for entering and ceasing restrictions may be separated (ie. shown as two or more lines instead of one). These measures. The diagram provides a simplified representation of two possible states for the system. and the limits set on them.On the other hand. These two states are shown as two zones – water restrictions applied. where the demand is equal to or greater than the yield. These are outlined as follows.
This equates to restrictions being imposed about once every five years.1) The Frequency of restrictions. a measure based on the number of years in which restrictions are applied is not a pure measure of restriction frequency. In most cases this would be expected to provide an estimate of frequency similar to the event based measure. for the purposes of illustrating the basic concepts. For example a single continuous period of restrictions lasting for three years out of ten would be measured as a frequency of 30% if based on the number of years. This is a measure of the number of occasions in a given period on which restrictions are applied. In this sense. This equates to 169 months out of a total of 600 months (ie. a total of 169 months were affected by restrictions over the entire 50 year period. for the supply system represented in Figure 2-2. or about 28% of months overall. in reference to Figure 2-2. The main problem with this as a measure of the duration of restrictions is that. it tends to incorporate both the number of restriction events and the duration of those events. For example. This can be based on the number of drought events experienced over a defined period that result in periods of restriction being imposed. For this reason it is a more difficult concept to grasp than the more direct measure outlined in the previous paragraph. for the hypothetical system. In practice. For example. this is often taken as the number of months in restriction over the entire period considered. as the longest period over which a particular restriction event occurred. the frequency of restrictions could be based on the number of years over the period in which restrictions applied. For example. However. 12 months times 50 years). this is a measure of how long restriction events are likely to be.DOC FINAL PAGE 12 . In its simplest form. This can be expressed. and only 10% if based on the number of events. rather than a direct measure of how long restrictions would be expected to apply. Alternatively. WC02486:FINAL REPORT JUNE 2003. as for measuring the number of years in which restrictions are applied. for example. that short durations of restrictions have been lumped together with other periods of restriction). and would typically be expressed as the number of months for which restrictions are applied in that event. The duration of restrictions can also be expressed as the total amount of time over a defined period for which restrictions are applied. in cases where single restriction events last for more than one year this will not be the case. with the measure based on years in restrictions also incorporating the impacts of the longer duration of the restriction events. 2) The Duration of restrictions. This effectively gives an estimate of the proportion of time over a long period in which we could expect restrictions to apply. on average. around 10 drought events can be identified where the total storage level dropped below the drought restriction trigger over the 50 year period depicted (the number of 10 drought events is approximate and assumes. such a measure is shown (labelled as "duration") in Figure 2-2 and Figure 2-3.
DOC FINAL PAGE 14 40 50 .n Figure 2-2 Hypothetical Water Supply System Behaviour 30000 Resilience 25000 Storage Volume (million litres) No Restrictions 20000 Drought Restriction Trigger Duration 15000 Stability Restrictions 10000 Severity 5000 Drawdown Period Storage Volume Drought Restriction trigger 0 0 10 20 30 Year WC02486:FINAL REPORT JUNE 2003.
Alternatively it may experience restrictions only once in that time but for 30 months. The further the storage level is drawn down.) and of the potential for the continuity of supply for basic needs to be threatened as a result of extreme drought.DOC FINAL PAGE 15 . An example of the latter measure is shown in Figure 2-4. etc. labelled "severity". WC02486:FINAL REPORT JUNE 2003. The duration of restrictions is 30 months out of 120 or 25%.Figure 2-3 Duration of Restrictions n 30000 Storage Volume (million litres) 25000 No restrictions 20000 Restrictions Duration 15000 10000 5000 0 8 9 10 11 12 13 14 15 Year The difference between the two types of measures discussed for duration may be illustrated by using an example of a system that for ten years experiences 3 months of restrictions for each of those years. The degree of inconvenience increases with the level of restrictions. and level 3 prohibit all watering except by hand-held hose. the more severe the level of restrictions that would apply and. and so on. Severity can be measured simply as the most severe level of restrictions that would be applied – this relates directly to the inconvenience and/or hardship resulting from the imposition of restrictions. hardship. importantly. Alternatively. A severity measure therefore provides insight into the degree to which the community will be affected by the restrictions imposed (inconvenience. This provides a measure of the extent to which the system storages may be drawn down during a period of drought. in addition. severity can be measured by the extent to which the storage volume has been reduced during a drought event – this can be related more directly to the risk of running out of water. the closer the system gets to running out of water. For example level 1 restrictions may only limit times of garden watering. Figure 2-4 also illustrates how increasing levels of water restrictions would be triggered as the water storage level progressively decreases. The percentage would also be 25% but the impact felt by consumers quite different given the length of time spent in one restriction period. level 2 may. prohibit watering of lawns. 3) The Severity of the restrictions.
There are also system performance measures that relate more to the planning and operational aspects of maintaining supply such that the level of service provided to the community meets the community's expectations. This provides a measure of the ability of the supply system to recover to a satisfactory condition after the end of a drought period.DOC FINAL PAGE 16 . on the characteristics of the system. as a consumer of water. as shown in 5 (labelled as "resilience). They are therefore typically the main focus for defining standards of service for water resource security. this could be defined as the length of time taken for the storage level to recover to full supply volume. The determination of what a "satisfactory" condition might be for a particular system will depend. WC02486:FINAL REPORT JUNE 2003. Alternatively. is most interested.Figure 2-4 Restrictions Severity n 30000 Full Supply Level Storage Volume (million litres) 25000 No restrictions 20000 Drought restriction trigger 15000 Restrictions Severity Level 1 Level 2 Level 3 10000 Level 4 Level 5 5000 0 8 9 10 11 12 13 14 15 Year The above measures would typically be those in which the general community. to a large extent. could be used. As an example. the time taken for the storage level to recover to a state where restrictions are lifted. These types of measures are outlined as follows. As would be expected. 4) The Resilience of the system. these measures tend to be of greater interest to water supply authorities than to the general community.
Figure 2-5 System Resilience n 30000 Full Supply Level Resilience Storage Volume (million litres) 25000 No restrictions 20000 Restrictions 15000 10000 5000 Resilience (alternative) 0 31 32 33 34 35 36 Year 5) The Drawdown Period. Such a measure is illustrated in Figure 2-2 (labelled as "drawdown period") and in Figure 2-6.DOC FINAL PAGE 17 . Figure 2-6 Drawdown Period n 30000 Full Supply Level Storage Volume (million litres) 25000 20000 No restrictions Restrictions Drawdown Period 15000 10000 5000 0 0 1 2 3 4 Year WC02486:FINAL REPORT JUNE 2003. This provides a measure of the time taken for the supply system to move from the full supply volume condition to a level where restrictions will be imposed.
duration and severity of restrictions) can be maintained over a range of climatic and operational conditions. Because improving this reliability costs money (and in addition has social and environmental implications) these criteria also WC02486:FINAL REPORT JUNE 2003. but for large urban systems is likely to be longer. this may involve the use of a number of performance measures. The area outlined in Figure 2-7 labelled as "stability" illustrates an extended period for the hypothetical supply system over which there is relatively frequent oscillation between restricted and non-restricted periods. frequency.3. Although a measure of the stability of the system could be of interest to the community. in practice it may be used by a water supply authority more as an indicator for internal operational purposes to ensure that explicit standards of service (eg. including measures relating to the frequency. This provides a measure of the degree of fluctuation between periods of restrictions and period of no restrictions within a specified (short) period of time.From a technical perspective the term critical drawdown refers to the period from the reservoir being full to the lowest point of drawdown during the critical drought. duration and severity of restrictions.DOC FINAL PAGE 18 . Typically. The period of time considered would be chosen based on the characteristics of the supply system and on the expectations of the community (nuisance effect of restrictions being repeatedly lifted and reimposed within relatively short periods of time). A combination of measures is required to ensure that all aspects of interest to the community are dealt with. no single performance measure will generally be sufficient to adequately represent the desired standards of service. this may be of the order of six months. Typically. 2. The critical drought is the worst drought on record. 6) The system Stability.1 The context of performance criteria Water resource security performance criteria express the community expectations about the reliability of their water supply. Figure 2-7 System Stability n 30000 Storage Volume (million litres) 25000 No restrictions 20000 Restrictions Stability 15000 10000 Moved in or out of restrictions fourteen times over twelve years 5000 0 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 Year Overall.
or risk. Because the supply is dependent on rainfall and associated catchment runoff to storage reservoirs. which varies every year. of not being able to continue supply without imposing water restrictions. inconvenience and disruption caused by water restrictions in preceding droughts.DOC FINAL PAGE 19 . which historically has been less important.reflect a trade-off between the social and economic costs of disruption to. and Memories of the cost. the water supply availability needs to be expressed in terms of a probability. in some cases. As such. the acceptance of higher levels of risk of supply shortfalls. WC02486:FINAL REPORT JUNE 2003. as it leads to "demand hardening" and an associated reduction in the efficacy of water restrictions. or shortfalls in. water supplies and the social and economic cost of taking measures to ensure those shortfalls do not occur. Those measures may comprise providing new water sources or reducing demands (demand management). Demand management implicitly incorporates higher levels of risk tolerance in water resource management. Recently there has been a growing awareness of the importance of considering the environmental cost of large water supply schemes. The level of risk of water supply shortfall that societies are prepared to tolerate varies and may depend on: q q The cost of supply augmentation. the pendulum has now swung away from developing new supply sources towards demand management and.
(c) The maintenance of adequate reserves of water by the Authority. and Management and protection of the Catchment Area and Catchment Infrastructure Works to promote water quality et al. To satisfy items (b) and (c) above Sydney Catchment Authority (SCA) has an obligation under Clause 8.". that the Authority [SCA] will meet in full Sydney Water Corporation's Forecast Average Annual Demand requirements referred to in paragraph (f)….1 of the Operating Licence refers to the Bulk Water Supply Agreement between Sydney Catchment Authority and Sydney Water Corporation. 1998 was passed which established the Authority in its role as catchment manager and bulk water supplier to the Sydney Water Corporation.the percentage of months." Schedule 2 of the Operating Lic ence specifies three performance criteria relating to long-term standards of service. The Sydney Water Catchment Management Act.DOC FINAL PAGE 21 .2 of its Operating Licence to: "…. SCA's Current Operating Licence and Performance Criteria Objectives 3. and set out its' responsibilities. on average.ensure that Catchment Infrastructure Works are designed. These were defined in the Sydney Catchment Authority Operating Licence which was issued under the Act and amended in April 2000 and are.1 Performance Criteria Sydney Catchment Authority was established in 1998 to separate the responsibility for Bulk water supply from those for water treatment and distribution which. (b) The continuity of the water supply. To conduct its operations in an ecologically sustainable manner. had all been undertaken by Sydney Water Corporation.1. historically. The terms of the Agreement include stipulations concerning (a) The standard of the quality of the water supplied. and (d) The cost to be paid by Sydney Water Corporation for the supply of water to it. in summary. as follows: q q q q Compliance with the Operating Licence and all applicable laws. Clause 5. WC02486:FINAL REPORT JUNE 2003. operated and managed to provide Sydney Water Corporation with a long-term standard of services which accords with the performance criteria set out in Schedule 2. To manage the Catchment Infrastructure Works efficiently and economically and in accordance with sound commercial principles.3. These are set out as follows: Reliability Reliability is defined in Schedule 2 as "….
this measure also includes mixes characteristics of a duration measure with the frequency measure (see discussion in Section 2.". A "year" is further defined in the relevant clause as "…. Robustness Robustness is defined in Schedule 2 as: "….333 years is it permissible for the modelled trajectory of the storage levels to be less than 5%." Effectively this means that for only one month in 8. on average... This means that "…. is to be not less than 5% …. that water restrictions may be applied.".000 months. on average.. restrictions will not need to be applied more often than 30 months in 1. on average. technically. it is estimated that. is to be not less than 90% . However. Security Security is defined in Schedule 2 as: "…. WC02486:FINAL REPORT JUNE 2003.. each period of 12 months commencing on 1 July …. on average. a measure of the frequency of restrictions with time measured on a monthly scale.3). over the long term). meaning that "…." This measure is another form of frequency measurement limiting the number of years." and a year will have been affected by restrictions "….". is to be not less than 97% .. The percentage of years. meaning that "….000 months.".The performance criterion specified for reliability is that it "…..001% of the time." The performance criterion specified for security is that it "…." This means that restrictions would not be in force for more than 3% of the time overall and is therefore.DOC FINAL PAGE 22 . not more than 10 years in 100 years will be affected by restrictions. On average. more often than 0. This criterion is intended to ensure that the system would not run out of water. the level of operating storage will not fall below 5% more often than one month in 100. The level of the Authority's [SCA's] operating storage below which actual storage is not to fall.." The performance criterion specified for robustness is that it "…. Paragraph (f) in Schedule 2 of the Operating Licence specifies Sydney Water Corporation's Forecast Average Annual Demand for the five years from 2000 to 2004 as shown in Table 3-1. given that a monthly timescale is very small compared to the overall period over which the performance is conceptually being assessed (ie.. on average. it is estimated that. if in any day of that year a restriction has been applied. that the Authority [SCA] will not require a reduction in Sydney Water Corporation's Forecast Average Annual Demand for Bulk Raw Water referred to in paragraph (f) ….
" Performance Criteria Objectives Discussions held with Sydney Catchment Authority indicated that the objectives for the performance criteria within their Operating Licence were as follows: q The fundamental objective was to ensure that the system would not run out of water. WC02486:FINAL REPORT JUNE 2003.05% of time. not more than 0. or last too long from the perspective of the community.DOC FINAL PAGE 23 .000 Paragraph (d) of Schedule 2 of the Operating Licence states that these performance criteria assume "….000 2003 584. This also raises the question as to what SCA can actually do to ensure that the criteria are met and hence what its obligations are.3% of time. Sydney Water Corporation will reduce its demand for water from the Authority in accordance with the following restriction levels: Level I Level II Level III Level IV Level V 3. In this respect the performance criteria should be interpreted in a context that includes the Drought Response Plan.3 Compliance with Performance Criteria IPART carries out an annual audit of SCA's compliance with the Operating Licence obligations for which SCA must demonstrate compliance with these performance criteria. not more than 0.000 2004 583. q q Clear documentation of the service standard to be provided to the community. not more than 0. not more than 3% of time. The performance criteria were originally an engineering device to assist planning which recently had also been adopted as a customer service standard. at least a 20% demand reduction.n Table 3-1 Sydney Water Corporation's Forecast Average Annual Demand as set out in paragraph (f).5% of time. That. Provision of an important tool for long term planning that indicates the need to bring available supplies and demand into balance.000 2001 588. the water restrictions to be imposed should not be excessively frequent. 3. at least a 50% demand reduction. This issue is discussed in Section 5.3. contingent upon the Authority [SCA] giving Sydney Water Corporation reasonable prior written notice of the need to do so. The criteria that govern the frequency. severe. q In achieving this primary objective. duration and severity of restrictions must be seen as a package in which the individual criteria can be traded off against each other to guard a minimum volume of storage and maintain supply continuity. at least a 30% demand reduction.2 at least a 7% demand reduction. not more than 1% of time. at least a 12% demand reduction.000 2002 586. The following deals with how compliance may be determined. Schedule 2 of SCA's Operating Licence Year 2000 Forecast Average Annual Demand (ML/year) 595.
These are then compared to the standard of service criteria to determine whether or not the system (as represented by the model) complies. in particular that they relate to performance. The SCA utilises a monthly water supply system simulation model developed to represent the behaviour of its supply system. whilst satisfying the supply security criteria. This model has been developed using the WATHNET simulation modelling software. on average. The very nature of the performance criteria. Similarly other factors influencing demand such as population change and climate change should be included in the projections to ensure they are as realistic as possible. such an assessment cannot be based on observed system performance. To assess this compliance. The present performance criteria do not specify whether the projected demands to be used in the model should be the average demands as stated in Table 3-1 or whether those demands should be adjusted to include climate induced variability. over the long-term. the model is run setting the annual demands on the system equal to the Sydney Water Corporation's Forecast Average Annual Demand (Table 3-1) and the performance measures outlined above (for reliability. and will tend to prevent over estimation of the system yield. the SCA WATHNET modelling provides a yield estimate of 600.1 Determining compliance In order to determine whether or not the SCA supply system complies with the longterm standards of service defined by the licence performance criteria. WC02486:FINAL REPORT JUNE 2003. 3.DOC FINAL PAGE 24 . This gives the annual volume of water that could be supplied from the system. Current practice is to use the former. Actual observations of system behaviour will typically be limited to only short periods of record over which system operation (including the level of demand supplied) is representative of the conditions relevant to the assessment. These observations will also only give a "snapshot" of how the system has performed over a relatively short period. means that some form of model must be used to represent the response of the system in supplying the required demands. robustness and security) are calculated from the model output. The WATHNET model of the SCA's supply system therefore provides the means by which compliance with the long-term standard of service criteria can be assessed. on average.3. an assessment must be made of the levels of service provided for the forecast average annual demands shown in Table 3-1. and will not provide a reliable guide of long-term performance. The inclusion of variable demands according to climatic conditions is considered more realistic.2 Yield estimation The yield of the SCA supply system is estimated by running the WATHNET model for different levels of average annual demand and determining that level of demand for which the system is just able to meet all the performance criteria. Based on the currently available information.3. From a practical perspective.3.000 million litres (ML) per annum for the SCA bulk water supply system in its current configuration and under current operating practices. It has been recommended (SKM 2003) that this practice be adopted in preference to current practice and this recommendation is endorsed here.
The performance criteria used by these organisations varied principally in relation to the rainfall variability and exposure to multi-year droughts of their region. Security of Supply Performance Criteria Elsewhere 4. which were considered to have similar conditions to Sydney (ie multi year storage. They were also requested to provide the underlying objectives of the performance criteria. In addition. These areas may be described as "non. n Table 4-1 Organisations contacted for survey of performance criteria Water Supply Agency Supply area ACTEW Barwon Water Brisbane Water/ Gold Coast Water Hobart Water Hunter Water Melbourne Water Power and Water SA Water Water Corporation of Western Australia Overseas Department of Water Affairs Metropolitan Water District of Southern California Canberra Geelong Brisbane Gold Coast Hobart Newcastle Melbourne Darwin Adelaide Perth Australia South Africa Los Angeles Respondents generally provided their performance criteria in terms of the specific criteria that they utilised to protect minimum storage levels and the maximum frequency. which tended to be the limiting constraint rather than the dams. and exposure to multi year droughts) were contacted.resource constrained". Very little information was provided on the objectives underlying those criteria and it appears likely that the criteria have been adopted on the basis of acceptance of conventional practice. duration and severity of restrictions. two overseas organisations.1 Non-resource constrained areas The focus in these areas was generally on the water delivery system.1 Performance Criteria used by the Bulk Water Suppliers A selection of the major bulk water supply agencies within Australia were contacted to provide the performance criteria that they use to manage and operate their water supply systems. Those with highly dependable supply systems that have the capacity to reliably supply all demands without restrictions did not utilise criteria similar to those for Sydney. as commonly river flows are sufficiently large and reliable to require minimal storage requirements.1. 4. The organisations contacted are listed in Table 4-1. high rainfall variability. This is in contrast to most areas in Australia which are "resource constrained". and where the supply systems do not have the capacity to supply all demands without restrictions in times of drought.DOC FINAL PAGE 25 . WC02486:FINAL REPORT JUNE 2003.4.
Some Australian water authorities also have. That authority adopts a policy objective as follows: Through the implementation of the Integrated Resources Plan. Not all authorities used all of the above criteria. effectively. The region's water supply is estimated to be 100 percent reliable during the next ten years. WC02486:FINAL REPORT JUNE 2003. q Not imposing restrictions for excessively long periods.2 Resource constrained areas The performance criteria used by authorities in areas where the water resource was more constrained. q Fairly detailed specification of the level of curtailment and differentiation between the different types of customer . q In one instance the minimum storage to be protected was stated as a proportion of the average annual demand rather than as a proportion of total storage. for which water should be provided at a very high level of assurance. and assume a 100 percent reliability of their water supplies with a "no failure" approach. MWD estimates the demands on its system to be 6 to 16 percent higher than the projections presented in the member agencies' urban water management plans (MWD. q Not imposing restrictions too frequently. and q Not imposing restrictions that are excessively severe.1. according to MWD (MWD 1996) there is an assurance that all demands for Southern California retail customers can be satisfied for all foreseeable climatic conditions over the next ten years.The Metropolitan Water District of Southern California (MWD) supplies water to a service area supporting over 16. to provide a "margin of safety". and some specified additional aspects: q A minimum duration for restrictions (of two weeks) to prevent customer confusion.DOC FINAL PAGE 26 . This model also recognised "strategic" water consumers. This policy is considered by the MWD to provide a solid foundation for a strong economy. and hence is not appropriate to adopt for Sydney. Furthermore. This approach is not suitable for resource constrained areas such as SCA's. They included criteria for: q Planning to ensure a minimum buffer storage would be maintained within the system as a contingency against a drought sequence more severe than could be foreseen based on the historic record. Metropolitan and its member agencies will have the full capability to meet full-service demands at the retail level at all times. This means that.for example. This additional allowance on top of the demand projections provides a further layer of supply assurance. 2003). were generally similar to those currently used for Sydney. between domestic and industrial consumers. requiring significant storage capacity.5 million people and a US$500 billion economy. non-resource constrained systems. such as power stations. MWD's current practice for implementing this is "to develop supplies that are available at least ten years in advance of need to ensure water supply reliability". 4. (Pers Comm. MWD).
2 are therefore relevant. The form of criteria discussed in Section 4.2 Relevance to Sydney's water supply system Sydney's system is resource constrained rather than non-resource constrained.DOC FINAL PAGE 27 .1. It is considered that the performance criteria in the SCA's Operating Licence generally cover the requisite areas conventionally used by bulk water suppliers for such systems. WC02486:FINAL REPORT JUNE 2003. The concept of linking the planned minimum storage to a proportion of average annual demand that is closely related to the time required to implement a drought contingency plan may be beneficial for (and worth further consideration in relation to) the Sydney system.4.
2).1. WC02486:FINAL REPORT JUNE 2003. 5. These secondary objectives aim at ensuring that the frequency. environmental and social/health consequences of such an occurrence would not be tolerated by a modern society.3. § Realism of the expected reduction in demand in response to restrictions – especially in the light of demand hardening following the introduction of water conservation measures. This objective is fundamental to all stakeholders. q Ensuring a continuous water supply requires that the supply authority has a robust Drought Response Plan. including allowance for environmental and other approval processes that may be required. A set of secondary objectives would then be required to focus on the level of disruption this may cause. Objectives Underlying Performance Criteria In order to ascertain the key objectives underlying the performance criteria. 5. These discussions. for resource constrained system such as the SCA's (see Section 4. a series of discussions were held with the organisations listed in Section 1.5.1 Objectives of Supply Authorities within Australia and Overseas The feedback received from the survey of urban bulk water suppliers is summarised as follows: q The community would consider it unacceptable for a large city to run out of water. are summarised in this section. To ensure the key primary objective (not to run out of water) is met would require. at least. § Allowance for possible water quality problems associated with low flow and low storage levels in the usual sources. that the water supply be curtailed in times of drought. combined with the responses from the survey of urban bulk water suppliers. The economic. § Allowance for the differing water security requirements of different types of consumers. duration and severity of those curtailments are not excessive for the consumers. It would need to be robust in.DOC FINAL PAGE 29 .2 Objectives Relevant to Sydney's system Figure 5-1 illustrates the relationships between the Sydney Catchment Authority and other key stakeholder organisations that are relevant in relation to its bulk water supply operations and in relation to the performance criteria. the following senses: q § Realism of lead times for the implementation of emergency supply augmentation. and § Allowance for modelling uncertainty.
There was general acceptance of the objectives for the performance criteria as outlined in Section 5.DOC FINAL PAGE 30 .n Figure 5-1 Inter-Organisational Structure: Sydney Catchment Authority IPART Operating Licence Regulator NSW GOVT DIPNR Water Managemnt Licence Regulator WAMC SYDNEY CATCHMENT AUTHORITY NSW Planning NSW Health EPA Hawkesbury. q The primary objective is to ensure that the system does not run out of water.1 above and restated below. WC02486:FINAL REPORT JUNE 2003.Nepean River Management Forum Independent Expert Panel Catchment Management Boards/ Committees CUSTOMERS (TREATED WATER) • Sydney Water Corporation • Wingecarribee Shire Council • Shoalhaven City Council OTHER CUSTOMERS (RAW WATER) Including direct supply of raw water from bulk water supply conduits eg Upper Canal System BUISINESS AND RESIDENTIAL CUSTOMERS Discussions were held with the key stakeholder organisations during the period from 7th to 9th May 2003.
§ It was unclear whether the system performance criteria belong in an Operating Licence given that the criteria relate to planning as opposed to operations. § It was unclear whether the inclusion of forecast water consumption was appropriate. As such they wished the criteria to be expressed in a manner that promoted the sustainable use of the resource. Managing of the demand. Table 5-1 is an indication that the anticipated savings may be over optimistic.DOC FINAL PAGE 31 .q The secondary objectives are to ensure that the frequency. Results were expected in October 2003. Ongoing review (particularly during drought operations) of the Drought response Plan and associated actions may result in different trigger levels for operational measures and actions for different parts of the supply system in order to maintain equal security of supply. This is not an explicit requirement of the Operating Licence. § SWC and the SCA endeavour to maintain equal security throughout all parts of the system. and § SWC is not wholly responsible for the demand for water. Although the projected savings are not directly comparable. in order to moderate it. Table 5-1 Anticipated savings from water restrictions Metropolis Melbourne Sydney Savings as percentage of average annual demand Level of Drought Voluntary Stage 1 Stage 2 Stage 3 Stage 4 Stage 5 restrictions 0 6% 11% 18% 22% N/A 0 7% 12% 20% 30% 50% Note: N/A means not applicable. Environment Protection Authority (EPA) § EPA's concern related to the environmental outcome of the performance criteria. q § SWC/SCA were conducting a survey on customer preferences on water conservation versus water restrictions. § It was necessary to review the assumed water savings in response to restrictions. WC02486:FINAL REPORT JUNE 2003. These had not been tested and would have been affected by demand hardening following the introduction of water conservation measures. duration and severity of water restrictions that may be anticipated in ensuring the primary objective is achieved are acceptable to the community being served. for example because of the difficulties it introduced if consumption in a given year exceeded the forecast consumption. required a "whole of government" approach to achieve maximum success. In addition some of the added perspectives were: q n Sydney Water Corporation (SWC) § The fundamental issue was "never" running out of water. Furthermore one of the objectives set for the Melbourne supply is that restrictions should never exceed Stage 3 restrictions. The use of the word "never" needed to be understood in the context of the Drought Response Plan which included a Contingency Plan. There was concern that the inclusion of the criteria may unduly limit operational flexibility.
Calculations to determine the environmental flow requirements are based on over 100 years of the flow regime. upon implementation. as these flows will be specified (in the Water management Licence) in terms of "transparent" and "translucent" flows which reflect inflows (see glossary for explanation of these terms). § EPA would prefer a whole of catchment approach that stated the whole yield of the system and apportionment to the environment and to all other users. As such. Potentially. 600 GL/year) so that it reflected the limited nature of the resource and provided a focus for demand management. Changes in the environmental flow requirements would most likely be accompanied by more stringent flow measurement and monitoring requirements. § The Hawkesbury-Nepean River Management Forum Expert Panel is looking at the potential impacts of environmental flow requirements on yield. § Security criteria should apply to all parts of the system equally. § There is a potential equity issue regarding water transferred from the Shoalhaven system. Hawkesbury-Nepean River Management Forum and Independent Expert Panel § The curtailment of environmental flows in times of drought is already addressed outside the SCA's performance criteria. substantially reduce the system yield below the current estimate of 600 GL/year (Hawkesbury-Nepean Management Forum (2003). § The criteria must adequately address competing uses for the water. It requires a "whole of government" approach.q § The way the performance criteria are currently expressed is undesirable. and § Before any changes were implemented to the criteria the cost implications would need to be assessed.DOC FINAL PAGE 32 . § Transparency and simplicity of the criteria to be adopted would be a key issue. The environmental flow options currently under investigation may. before the introduction of restrictions (stage 1) at 55% of overall system storage. Separate criteria are not required for the environmental flows. means that the water resources in the Shoalhaven system may become stressed before restrictions are commenced in the Sydney Metropolitan supply system. § EPA would prefer the sustainable yield to be explicitly stated (eg. periods of drought are already taken into consideration. § The security criteria are currently too generic – different water supply securities were suggested for different types of water use. § The Forum is also interested in the issue of whether some areas may not (due to the more isolated nature of their connection to the system) currently meet the supply performance criteria. WC02486:FINAL REPORT JUNE 2003. § Demand management cannot be carried out by Sydney Water alone. this could be supported by cost differentiation between different levels of security. as they appear to be demand driven rather than supply limited. Setting the pump mark (see glossary) to 60%.
§ The performance criteria should be matched to the performance criteria for Sydney Water. § The joint survey to establish customer preferences on water restrictions. which seem to relate more to an obligation to ensure that supply can meet (potentially increased) levels of demand into the future. § Sydney Catchment Authority echoed many of the issues raised by Sydney Water. Sydney Catchment Authority § Sydney Catchment Authority consider that it is appropriate for the performance criteria to remain within the Operating Licence. These included: § The need to review water savings that could be achieved by imposing water restrictions in the light of demand hardening and other issues. § The need to simplify the criteria to make them easier to understand.§ q Shoalhaven Water and Wingecarribee Shire Council § q q The performance criteria need to be considered more broadly in terms of all users of water across the catchment. It is anticipated that the broader water allocation requirements for the catchment would be accounted for in the Water Management Licence specifications. and be complementary to them so that the two organisations are not driven in opposite directions.DOC FINAL PAGE 33 . as they provide an important indicator of the standard of service to be provided to customers. by itself. This is because they also have alternative sources that have different characteristics to the SCA sources. This also provides an enforceable vehicle that is regularly monitored. This would provide a clear and transparent statement of the yield and establish the SCA's accountability to operate the system consistent with providing that yield. The SCA's performance criteria should focus on supply management and Sydney Water's on demand management. This is in contrast to the specifications in the current Licence. § Sydney Catchment Authority advises against reducing the level of reliability from 97% to 95%. and § Sydney Water. as this reduces the contingency for modelling uncertainty and the likely overoptimistic estimates for water savings from restrictions. and should not have constraints that may not be relevant governing the operation of their systems. they do not consider it appropriate to incorporate security of supply for their systems in the SCA Operating Licence. Although these two organisations source a significant amount of their bulk water supply from the SCA's system. and § It is considered that it may be useful to include the yield estimate together with the criteria in order to provide a focus for demand management. A "whole of government" approach is required for this. WC02486:FINAL REPORT JUNE 2003. could not control the demand for water. § Their joint operational endeavours to maintain equal security across the entire system. Ministry for Energy and Utilities § It is appropriate for the performance criteria to remain within the Operating Licence to reassure customers that their water supply is safe.
That the performance criteria need to be simplified in order that they can be more easily understood.4 Summary The discussions with key stakeholder organisations provided a clear consensus regarding the nature of the objectives for the performance criteria. Traditionally the focus was on increasing supply to match demand. q Management of the system in a manner that is consistent with maintaining the existing yield and ensuring that appropriate practices for assessing system performance and estimating yield are used. from demand driven to supply limited management. 5. duration and severity of water restrictions that may be anticipated in ensuring the primary objective is achieved are acceptable to the community being served. duration and severity of restrictions) to the community. the perceived community expectations regarding the behaviour that the Licence should promote are: q Not to increase yield by developing new sources. There were also a number of issues of which (as they were not addressed in each of the discussions) it cannot be said that there is clear consensus. by ensuring that the level of demand does not exc eed available supply. q The environmental water requirements are being addressed by the HawkesburyNepean Management Forum. whilst maintaining a certain desired level of service (in terms of frequency. Community expectations have now changed – there is a shift to managing within the available developed resources – that is. alternatively.DOC FINAL PAGE 34 . and § The secondary objectives would be to ensure that the frequency. and q Working with other Authorities/bodies to ensure that water demand management.5.3 How Should These Objectives be Achieved? The key objectives outlined relate to not running out of water. q That environmental flows be released in accordance with the requirements of the Water Management Licence. These are summarised as follows: q q There should be the following primary and secondary objectives: § The primary objective is to ensure that the system does not run out water. Whereas currently the Licence obligations on the SCA appear to reflect the need to adjust (increase) supplies to meet (increasing) demand. They are being formulated in a manner that will implicitly address the management of the release of the environmental water WC02486:FINAL REPORT JUNE 2003. However. and water recycling and reuse strategies are in place. These can be achieved by ensuring there is sufficient water available to meet demand or. these issues are unlikely to be contentious and are outlined as follows: q The anticipated water savings that may be achieved by introducing water restrictions are overly optimistic and should be reviewed.
and the need to. q That the performance criteria should be complementary to those applicable to Sydney Water. as is the case for most operating performance criteria).1. It is recommended that these issues may be more appropriately addressed in the Drought Response Plan and/or in specific bulk water supply agreements between the SCA and its direct customers (retail water suppliers). q The inclusion of the estimated yield (currently 600 GL/year) together with the performance criteria. that equal assurance is maintained to all consumers. maintain equal supply assurance across the whole system. Whereas the SCA and SWC endeavour to ensure. q The desirability of. Although it is not possible to assess the performance criteria directly in an operational sense (ie. There was not agreement over the following issues: q Sydney Water Corporation expressed reservations about inclusion of the performance criteria within the Operating Licence. this issue is pertinent to the supplies to the Nepean and Illawarra WFPs and some centres supplied from the Blue Mountain Reservoirs. based on observed performance over previous periods. WC02486:FINAL REPORT JUNE 2003. which receive supplies from Tallowa and Wingecarribee Reservoirs respectively. operationally. q It would be desirable to state the sustainable yield of the system together with the performance criteria in order to promote the sustainable use of the resource. Shoalhaven Water and Wingecarribee Shire Council.3. given that the criteria relate to planning as opposed to operations. have indicated their preference not to be included within the Operating Licence arrangements.requirements in times of drought. All other organisations interviewed expressed the opinion that it was appropriate for the performance criteria to remain within the Operating Licence as it documented important customer service standards within an audited vehicle.DOC FINAL PAGE 35 . In practice. at times this may not be totally achieved. they can be assessed using the supply system modelling techniques discussed in Section 3. They therefore do not need to be explicitly covered by the Performance Criteria.
§ Customer and consumer relations. 6. Options for Adopting Appropriate Security of Supply Criteria for Sydney 6. Memoranda of Understanding (MoUs). Planning and Natural WC02486:FINAL REPORT JUNE 2003.DOC FINAL PAGE 37 . The SCA must conduct its activities in accordance with the Operating Licence. There are a number of regulatory and legislative instruments. The list below refers specifically to the supply to Sydney Water Corporation.2 Interactions with Other Relevant Regulatory and Legislative Instruments The role and responsibilities of the SCA are established by the provisions of the Sydney Water Catchment Management Act 1998 and Regulations. and § Environmental management. which govern the operation.1 Desirable Attributes of Performance Criteria The performance criteria to be adopted for use in an auditable vehicle should have the following attributes: q q Clarity: The criteria should be easy to understand and unambiguous. and its terms are subject to review. Regional Environment Plan and plans of management – to assist in the operation of the SCA (IPART. § Management of bulk water quality. The current Licence has effect until 31 December 2004. q Controllable: the targets set by the criteria should measure parameters that are within the control of the Authority. 2003). The annual operational audit checks performance compliance for: q § Maintenance of the various Memoranda of Understanding. and q Relevant: the criteria should be relevant and important to the Authority and its customers. The Water Management Licence. The SCA's compliance with the obligations under the Licence is audited annually by IPART. planning and management of the bulk water supply infrastructure. § Management and protection of the catchments. q Achievable: The criteria should be realistic to the extent that they are achievable. q Operating Licence.6. The SCA's Water Management Licence was issued by the former Department of Land and Water Conservation (now the Department of Infrastructure. Measurable: The degree of performance should be capable of being measured in a consistent manner. § Management of catchment infrastructure and demand management. The Act establishes a number of sub-ordinate instruments – the Operating Licence. and management plans. which accounts for more than 99% of the water supplied to customers from SCA's system.
These provide the structure and processes for cooperative interaction with those bodies.DOC FINAL PAGE 38 . It outlines objectives for the SCA in relation to access to water resources within its area of operations and establishes the platform for environmental flows to be released from SCA infrastructure. the SCA also serves more than 50 additional customers. 2) Option 2: Rephrase the existing criteria.Resources . such as the SEPP 58 – Protecting Sydney's Water Supply. In addition to Sydney Water Corporation. there are important instruments.DIPNR). and outlines options and an action plan for maintaining system operation to meet the required levels of service over the medium term. 4) Option 4: Develop a set of Primary and Secondary criteria that explicitly states the system yield. q The Drought Response Plan. Memoranda of Understanding have been drawn up between the SCA and the NSW Environment Protection Authority (EPA). with the objective of maintaining adequate water supply security. with separate agreements for these customers regulating those relationships. by developing a set of Primary and Secondary criteria relating directly to the key objectives identified in this review. This plan describes the planned actions in the event of prolonged below average inflows to water storages. This plan documents the configuration and operation of the SCA's bulk water supply system. the Illawarra. and WC02486:FINAL REPORT JUNE 2003. the Southern Tablelands and the Blue Mountains. 5) Option 5: Use the system yield itself as the principal criterion. with basically similar content. aimed primarily at protecting water quality. The options listed below encompasses the main issues identified in the review: 1) Option 1: Retain the existing criteria. q The Bulk Water Supply Agreement.3 Appropriate Combinations of Criteria There is a range of options for the revised performance criteria that may be adopted for inclusion in Sydney Catchment Authority's Operating Licence. including its function and infrastructure arrangements. which further regulate the SCA's operations. which covers the conditions under which water is supplied by the SCA to SWC. It focuses on operations to deliver the required volumes of raw bulk water for metropolitan Sydney. It is a requirement of the Bulk Water Supply Agreement and was developed by the SCA in consultation with SWC. the Water Administration Ministerial Corporation (WAMC) and NSW Health. 3) Option 3: Develop a set of Primary and Secondary criteria that includes distinction between the different levels of security that may be required by different users. q The SCA's Bulk Water Supply Network Plan. This is an agreement between the SCA and Sydney Water Corporation (SWC). Furthermore. 6.
q A set of criteria. These options and their associated issues are discussed in the following sections of the report. Currently.3. however. Specification of different standards of service to apply WC02486:FINAL REPORT JUNE 2003. 6. 6.for example restriction measures may need to be amended if found to be less effective than anticipated. however. For example.1 Option 1: Status Quo Option 1 is not acceptable as the present wording is unclear. and include a criterion regarding maintenance of equal supply assurance throughout the system. ambiguous in some respects. Under this option. The criteria would be expressed in the following form: q The primary (maintaining supply continuity) and secondary (minimising societal disruption caused by water restrictions) objectives. as experience with severe restrictions is limited especially in an environment where extensive measures for demand management have been instituted. system (see Section 5. They suffer . There is also a concern that the existing criteria and the framework in which they are presented are not consistent with providing a mechanism encouraging the SCA to operate its bulk water harvesting and delivery system as a supply limited. which are stated in Schedule 2 of the Licence along with the performance criteria. from lack of clarity. comprising primary (protecting a buffer supply) and secondary criteria (the frequency. 6.3. where the need to amend the restriction rules occurs. Overall. the planned restrictions may not achieve the desired savings and may therefore need to be amended. This scenario is highly likely during periods of severe drought. and "demand hardening" has occurred. as it will impinge undesirably on operational flexibility . and not easy to understand.DOC FINAL PAGE 39 .6) Option 6: Develop a set of Primary and Secondary criteria. Difficulties may arise with this approach.3).3. domestic outdoor use may be restricted more often or more severely than industrial use.2 Option 2: A Set of Primary and Secondary Criteria The existing criteria do address the principal issues of maintaining supply continuity whilst using water restrictions that are not excessively frequent. In practice. the basic content of the performance criteria would be retained whilst eliminating the lack of clarity and ambiguity. effectively defining different standards of service to apply to different categories of water use. this information underlies the anticipated percentage demand reductions for each level of water restrictions. long or severe. This type of information is relevant to consumers and could potentially be included as specific performance criteria. rather than as a demand driven. duration and severity of water restrictions).3 Option 3: With Distinction of Security Specifications for Different Types of Use Option 3 would provide for explicit specification of the probability of restrictions being applied for different categories of water use. this option is not recommended. or than use by strategic and essential service consumers such as hospitals.
This could then be used to provide a direct link to setting meaningful demand management targets.3.6 Option 6: Maintaining Equal Supply Assurance Across the Entire System Performance criteria reflect community expectations about the desired reliability of their water supply system and the trade off between the cost of water restrictions and the cost (including social. system. It is conceivable that the cost trade off relationship differs in different parts of the SCA water supply system. 6.3. and that the supply system should be managed so as to maintain the existing system yield. The inclusion of the system yield as part of the performance criteria could further be used as a mechanism for more clearly focusing the SCA's obligations in relation to community expectations that: q q new supply sources should not be developed to increase system yield.DOC FINAL PAGE 40 . In practice however this is likely to be impractical. Given that this option provides no transparency in terms of the actual level of service the community can expect to receive. it is not recommended for further consideration. 6. This approach is considered beneficial and is recommended for further consideration. and that it is sufficient to state the system yield by itself without also referring to the criteria. 6. however do represent an important standard of service and conceivably the same yield could be achieved with a different combination of criteria. The criteria. From an equity perspective. and would provide a clear focus for demand management needs.3. rather than as a demand driven. and therefore that maintenance of equal supply assuranc es across the entire system may not necessarily be beneficial overall. it could be argued that all consumers should be treated equally and that if equal service levels cannot be maintained then differential tariffs should be introduced. and would WC02486:FINAL REPORT JUNE 2003. This would explicitly recognise the imperative to manage system demands within the available resource. environmental and economic) of matching supply with demand. the performance criteria This would provide an explicit basis for the SCA to manage and operate its bulk water harvesting and delivery system as a supply limited. which would be relevant for Sydney Water Corporation's Operating Licence and other "whole of government" initiatives.to different categories of water use may be more effectively included in specific bulk water supply agreements or in the SCA's Drought Response Plan.5 Option 5: System Yield Only It could be argued that the performance criteria are the rules for determining the system yield.4 Option 4: Stating the System Yield The objective of stating the system yield along with the performance criteria (with the criteria specified as outlined above for Option 2) would be to emphasise the limited nature of the available resource.
(b) The storage level to provide allowance for modelling and other (eg climate change) uncertainties. and water quality and hydraulic considerations. with clarification. It would ensure that adequate supply (ie. whilst maintaining supply continuity with level 5 restricted demands. The preferred option recommended for further consideration is option (a). this issue should be addressed as an operational consideration within the SCA's Drought Response Plan. as a minimum would meet basic public health needs) could be maintained at least until the contingency plan has been implemented. that which. It is therefore recommended that an equal supply security criterion should not be included in the SCA's Operating Licence. This level would include allowances for modelling and other uncertainties.be likely to increase infrastructure and operating costs relative to other potentially more efficient options for managing this equity issue. and supplemented by addition of the system yield with the objective of promoting sustainable use of the available water resources. 6.1 What is Appropriate as the Buffer Storage Level Three alternatives were considered for defining the minimum storage level to serve as a buffer to ensure supply continuity. (c) The storage level below which SCA can no longer guarantee demands can be met by the supply (ie effectively run out of water). the preferred option recommended for further consideration is Option 4. which incorporates the criteria specified for Option 2 along with an explicit statement of the system yield. This would allow for the basic content of the existing criteria to be retained. 6. It would provide sufficient time for implementation of the contingency plan. These alternatives are: (a) The storage level defining the trigger for implementation of the contingency plan. or in specific bulk water supply agreements. Rather. as this represents an extremely meaningful point at which a decision would need to be made to proceed with (and commit funds for) implementing the steps outlined in the (emergency) drought contingency plan. It would also be likely to result in committing the community to potentially costly system augmentation needs for very little marginal benefit.4.DOC FINAL PAGE 41 . WC02486:FINAL REPORT JUNE 2003. It would include allowances for water quality and all hydraulic considerations given the significant storage depletion that would prevail. Imposing an equal supply security criterion in the Operating Licence is likely to reduce the existing operational flexibility that the SCA and Sydney Water currently rely upon to manage this issue equitably across the entire supply system.4 What is appropriate for SCA's Operating Licence? Based on the discussion above.
7. a Drought Response Plan (and associated demand restriction rules) provides for further protection of the storage levels in the supply system. and q Severity of restrictions. the city will not run out of water). The primary objective relates to providing the community with the reassurance that they will not run out of water. q Where longer duration drought periods occur. These relate. and to WC02486:FINAL REPORT JUNE 2003. In summary. The secondary objective relates to minimising (to the extent required by the community) the inconvenience and cost to the community associated with implementing drought response and/or emergency measures. The specific obligations of the SCA. so as to clearly communicate the supply limited nature of the supply system managed by the SCA. and q In cases of extreme. Inclusion of an explicit statement of the estimated system yield satisfying these criteria could also be included in the Licence. that is adequate. given its constraints in terms of expanding the available supply. to setting standards of service for the expected: q Frequency. it is recommended for further consideration that the criteria be categorised as satisfying primary and secondary objectives.DOC FINAL PAGE 43 . There are three main components to this: q The supply system itself has the capacity to maintain a level of supply. in particular. prolonged drought. based on the outcomes of the review and on feedback from the key stakeholders. Expressing the Criteria 7. a workable Contingency/Emergency Plan exists that ensures that measures can be introduced such that the basic water needs of Sydney will continue to be met indefinitely (ie. over most periods. would be to: q Ensure that the system is operated consistent with maintaining the stated yield. It is proposed that the general form of the criteria should cover three important areas.1 Proposed Form and Content The criteria should be expressed in every day language. and 3) Statement of system yield. 2) Statement of the Performance Criteria with associated relevant information. q Duration. as follows: 1) Introduction and Statement of the Performance Criteria Objectives. avoiding technical jargon.
with other organisations. In addition.DOC FINAL PAGE 44 . and sufficient pressure. that is. This clause could be maintained as it is. and water recycling and reuse strategies are in place.3. 7.2 The Authority must ensure that Catchment Infrastructure Works are designed. Management of Catchment Infrastructure Works.1. operated and maintained to provide Sydney Water Corporation with a long-term standard of services which accords with the performance Criteria set out in Schedule 2. Suggested revised text for Schedule 2 is as follows: Catchment Infrastructure Works Performance Criteria 1) Introduction and Objectives of the Performance Criteria These performance criteria. and q To actively work with other Authorities/bodies to ensure that appropriate water demand management. If included in the operating Licence. consideration should be given to the overall framework surrounding the criteria and to the obligations of the SCA under the Licence. that the supply can continue to meet the restricted demand requirements catering for basic water needs. q That the modelling procedure used to assess performance of the system against the Performance Criteria specified in Schedule 2 must be consistent with appropriate and acceptable industry practice. in relation to any demand management initiatives that may be required to ensure that overall system demands do not exceed the available system yield. to meet the requirements of the Water Management Licence. The statement of the available yield figure in the SCA's Operating Licence could therefore serve to establish meaningful demand management targets for the overall Sydney water supply system.2 Example The current referral clause in the main text of the Operating Licence is as follows: 8. these obligations would most appropriately be included as sub-clauses under the current Clause 8. WC02486:FINAL REPORT JUNE 2003. with water of acceptable quality.q Be actively involved. as required. with the key revisions focusing on the content of Schedule 2. to all parts of the supply system. together with the SCA's Drought Response Plan: (a) Have the primary objective of ensuring that the water supply system should not run out of water. These issues are discussed in Section 5. q In addition to operating the supply system consistent with providing the yield as specified in Schedule 2. consideration should be given as to whether the Operating Licence should be amended to reflect the following obligations (relating to the Performance Criteria) on the SCA: q To ensure that the system is operated consistent with maintaining the yield stated in Schedule 2.1. specifically for the release of environmental and riparian flows. As such.
Restrictions for continuous periods exceeding 24 months (for example) shall not be required. Restrictions will not need to be applied. particularly given that the community can easily make direct comparisons with publicised storage levels at any time. shall include a contingency plan. A Drought Response Plan. The probability of the system storage levels falling to the buffer storage level shall not exceed 1 occasion in 1. or for excessively long periods. or more directly as a percentage of total system storage ("y%"). severity and duration of water restrictions that may be anticipated. WC02486:FINAL REPORT JUNE 2003. (b) Water restrictions frequency. and other factors. The size of the buffer storage could be determined as recommended in Section 6. (d) Water restrictions severity: Level V (for example) water restrictions shall not be required more often. The system shall be operated.4. (c) Water restrictions duration. triggered by impingement of the storage buffer. adjusted to reflect climatic conditions.1. and (d) Are intended to promote the sustainable use of the available water resources. Because of the uncertainty around future climatic conditions. The performance of the supply system against the criteria is assessed using a computer model of the water supply system that can estimate the likelihood of certain events occurring. on average. The restricted level of demand to be supplied during that period ("x" months) could be defined based on expected demands at the highest level of restrictions. on average. The size of the buffer storage to be maintained could be expressed either as a number of months ("x") of restricted demand. from time to time. drawn up in collaboration with Sydney Water Corporation. more than once in 200 years (for example). too severely. or based on a specified minimum requirement for basic health needs ("z" litres/capita/day for "x" months). The model uses the projected average water demands. to ensure that basic supplies can continue to be met for an indefinite period.000 years (for example). with "x" being defined based on the length of time taken to implement the contingency plan responses. on average. based on the above criteria. The latter approach is more straightforward and more easily understood. than once in 200 years (for example).DOC FINAL PAGE 45 . (c) Describe the standard of service to be provided to customers in terms of the frequency. based on the preferences of the customers. more often than once every ten years (for example). by the system modelling). the current pattern of demands and the restriction rules stated in the Drought Response Plan. there is a degree of modelling uncertainty which is allowed for in the performance criteria.(b) Achieve this objective without imposing water restrictions too frequently. to provide an average yield of 600 GL/year (or such other figure as may be determined as required. A minimum operating storage equivalent to x months of total restricted demand (or y % of storage) shall be maintained as a buffer to assure supply continuity. 2) Performance Criteria (a) Supply Continuity.
at least a 12% demand reduction. and the maximum percentage of time for which each level may be applied.5% of time. It also should be updated regularly as water demand patterns and levels change. Removing these from the Operating Licence and including them in the Drought Response Plan (referred to by the Licence) provides greater flexibility for ongoing review of restriction rules to ensure appropriate operational management can be maintained during periods of drought. that the detailed information regarding the levels of water restrictions illustrated below be removed from the operating Licence and transferred to the Drought Response Plan. and as further information becomes available regarding the realistic demand reductions that can be achieved under restrictions.3% of time. not more than 0. It is further emphasised. publicly accessible document. This would ensure that transparency is maintained for the public in relation to the current levels of demand the system is subjected to and on the likely future levels of demand. This would explicitly acknowledge the supply side limitations and the importance of appropriate and sustainable management of the overall supply system by clearly setting out the demand management needs. not more than 0. It is considered that this information is too detailed for incorporation within the Operating Licence. not more than 1% of time. at least a 30% demand reduction. rather than on ensuring the supply can meet the demands into the future. not more than 0.3 Information Recommended for Removal From Schedule 2 of the Operating Licence It is recommended for further consideration as part of the End of Term Licence Review. WC02486:FINAL REPORT JUNE 2003. at least a 20% demand reduction. and how these compare to the demand management targets and the system yield stated in the SCA's Operating Licence.DOC FINAL PAGE 46 . that the projected system demands should be clearly specified in some other relevant. Likelihood not more than 3% of time. at least a 50% demand reduction. It is considered that the emphasis should be placed more on the sustainable yield the system can supply (as a means of setting meaningful and practical objectives and targets for demand management initiatives).7. In addition to specifying the anticipated demand savings for each water restriction level. It is also recommended that information on the projected system demands be removed from Schedule 2 of the operating Licence.05% of time. Restriction Level Level I Level II Level III Level IV Level V Expected Demand Reduction at least a 7% demand reduction. consideration should be given to adding a maximum percentage of time that infringement of the safety buffer storage zone may occur. however.
There is potential to include a more specific statement of the SCA's obligations under the Operating Licence. 8. Conclusions and Recommendations The following conclusions and recommendations are made following the discussions and investigations that have taken place during the course of this study. remove ambiguity and emphasise the requirement to manage the available water resources in a sustainable manner. 8.1 Conclusions q The current set of performance criteria should be modified to increase their clarity.2 of this report be taken forward for further consideration as part of the End of Term Review of the SCA's Operating Licence. and water recycling and reuse strategies are in place. This would provide clear and unambiguous drivers encouraging the SCA to operate its bulk water harvesting and delivery system in a manner consistent with current community expectations. That the modelling procedure used to assess performance of the system against the Performance Criteria specified in Schedule 2 must be consistent with appropriate and acceptable industry practice.DOC FINAL PAGE 47 . q That consideration be given as to whether the Operating Licence should be amended to clearly reflect the following obligations on the SCA (potentially included as sub-clauses under the current Clause 8. q The investigations conducted for this report have identified community expectations about the management of the water supply system that do not fall specifically within the ambit of the performance criteria themselves. q The demand reductions postulated for the various levels of water restrictions are considered to be overly optimistic. reflecting management of a supply limited rather than a demand driven system. WC02486:FINAL REPORT JUNE 2003. q That the implications of the proposed Performance Criteria be investigated to ensure they are achievable within the context of current policy.1): − − − − To ensure that the system is operated consistent with maintaining the yield stated in Schedule 2. to meet the requirements of the Water Management Licence.2 Recommendations The following recommendations are made: q That the revised Performance Criteria as drafted in Section 7. but rather relate to the framework surrounding the criteria and to the obligations of the SCA under the Licence. specifically for the release of environmental and riparian flows. These issues are discussed in Section 5.8.3. 2003). In addition to operating the supply system consistent with providing the yield as specified in Schedule 2. for example as stated by the NSW Premier in March 2003 (Premier of New South Wales. and To actively work with other Authorities/bodies to ensure that appropriate water demand management.
currently included with the Performance Criteria.DOC FINAL PAGE 48 . q That the table of water restriction levels. no be longer included in the SCA's Operating Licence. be omitted from Schedule 2 of the Operating Licence and carried over to the SCA's Drought Response Plan.q That the water demand projections. relevant and publicly accessible document. q That the modelling procedure used to assess performance of the system against these criteria must be consistent with acceptable industry practice. for example it should incorporate the impact of climate variability on the system demands. showing anticipated savings and average occurrence probability. WC02486:FINAL REPORT JUNE 2003. but be transferred to an alternative. q That the anticipated demand reductions following the implementation of water restrictions should be reviewed in the light of the introduction of water conservation measures and other factors.
DP. Stedinger. IPART 2002.. B. IPART 2002. Robustness of Water Resource System Performance Evaluation. Drought Management Plan for Victoria's Water Resources: General Applicability of Water Supply Performance Measures: Background Report L2. Metropolitan Water District of Southern California (2003). JR. Premier of New South Wales. Mid-term Review Workshop of the Operating Licences for Sydney Water Corporation and Sydney Catchment Authority. Drought Management Plan for Victoria's Water Resources: Risk in Water Supply Headworks Planning and Management: Background Report L1. Sydney Catchment Authority: Operational Audit 2001/2002. (2003). G. Loucks. Stedinger.DOC FINAL PAGE 49 . JR. Hashimoto. Rhodes. WC02486:FINAL REPORT JUNE 2003. January 2003. (1993). 1982b. Reliability. November 2001. MWD. Sydney Catchment Authority: Operational Audit 2000/2001. T. Water Resources Research. (1992). July 2001. Water Resources Research. Victoria (1996). Hashimoto. Rhodes. Volume 18 No 1 pp 14-20. Report to Minister of the Environment. Metropolitan Water District of Southern California (1996). June 1996. News Release. Southern California's Integrated Water Resources Plan.. Loucks. IPART 2003. B. September 2002. 23rd July 2002. 20th March 2003. T.Bibliography Blake Dawson Waldron 2001 Drought response Plan for Melbourne Retail Companies. Report on Metropolitan's Water Supplies: A Blueprint for Water Reliability. DP 1982a. March 2003. Resiliency. IPART 2001. Report No 1107. Volume 18 No 1 pp 2126. Water Industry Performance Standards Review.G. Hawkesbury-Nepean Management Forum (2003). March 1996. Mid-term Review of Sydney Catchment Authority's Operating Licence. Department of Water resources Victoria February 1993. May 2003. Progress Report on Stage 3 of the Work Plan. Department of Water resources Victoria January 1992. and Vulnerability Criteria for Water Resource System Performance Evaluation. Office of the Regulator-General. Blake Dawson Waldron Bulk Water Supply Agreement: Melbourne Water Corporation/ Yarra Valley Water Limited.
Merz (2003). Sydney Water Corporation. B. and Rhodes. Sydney Catchment Authority (June 2002). Letter dated 24 April 2003. May 2003. Personal Communication Metropolitan Water District of Southern California.. Stephen Arakawa. Drought Response Plan. Hunter Water Corporation. A Methodology for Developing restriction Rule Curves for Complex urban Systems. Manger Water Resource Management.Sinclair. (1999). Knight. Minutes of meeting held on 9th May 2003. Yurisich.G. R. Letter dated 14th May 2003. Report for Sydney Catchment Authority. Brisbane July 1999. Paper presented at Water 99 Joint Congress. Brendan Berghout. Independent Review of SCA's Water Supply Systems Model WATHNET.DOC FINAL PAGE 50 . Strategic Planner. Sydney Catchment Authority (April 2000). WC02486:FINAL REPORT JUNE 2003. Operating Licence.