lachlan water resource plan – sustainable diversion limit … · 2018. 11. 25. · streamflow and...

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LACHLAN SURFACE WATER RESOURCE PLAN

Sustainable diversion limit scenario model

Appendix C to Schedule F


NSW Department of Industry | INT18/192694 | i

Published by the NSW Department of Industry


First published November 2018

INT18/192694

More information

Perlita Arranz / NSW Department of Industry / Parramatta

industry.nsw.gov.au/water

Acknowledgements

[https://www.environment.nsw.gov.au/ieo/Lachlan/maplg.htm]

© State of New South Wales through the NSW Department of Industry 2018. You may copy, distribute, display, download and otherwise freely deal with this

publication for any purpose, provided that you attribute the Department of Industry as the owner. However, you must obtain permission if you wish to charge others

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website. You may freely link to the publication on a departmental website.

Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (November 2018) and may not be accurate, current or complete. The State of New South Wales (including the NSW Department of Industry), the author and the publisher take no responsibility and will accept no liability, for the accuracy, currency, reliability or correctness of any information included in the document (including material provided by third parties). Readers should make their own inquiries and rely on their own advice when making decisions related to the material contained in this publication.


NSW Department of Industry | INT18/192694 | ii

Contents Version history ........................................................................................... Error! Bookmark not defined.

Approval ...................................................................................................... Error! Bookmark not defined.

Glossary ................................................................................................................................................. iv

1 Introduction ..................................................................................................................................... 1

1.1 The Sustainable Diversion Limit scenario ................................................................................... 2

1.2 Purpose of report ........................................................................................................................ 2

2 Model development ......................................................................................................................... 3

2.1 Pre-2009 .................................................................................................................................... 3

2.2 Revisions to model ..................................................................................................................... 3

2.2.1 Post-2009 ............................................................................................................................ 3

2.2.2 Difference of SDL from PBP ................................................................................................ 4

3 Valley SDL number .......................................................................................................................... 5

4 Results and demonstration of SDL compliance ............................................................................ 6

4.1 Long-term simulation results....................................................................................................... 6

4.2 Description of representation of HEW ......................................................................................... 6

4.3 SDL Compliance and current water recovery ............................................................................. 7

4.3.1 Calculation of permitted take ............................................................................................... 7

5 SDL key model parameters ............................................................................................................. 9

6 References ..................................................................................................................................... 12


NSW Department of Industry | INT18/192694 | iii

Figures

Figure 1-1. Lachlan River Catchment ....................................................................................................... 2

Tables

Table 1. Comparison of modelled results from updated BDL and SDL scenarios (1985–2009) ................ 6

Table 2. Estimates of NSW and Commonwealth HEW via LTDLE Factors ............................................... 7

Table 3. Calculation of annual permitted take using SDL model ............................................................... 8

Table 4. SDL infrastructure and development parameters ........................................................................ 9


NSW Department of Industry | INT18/192694 | iv

Glossary Term Definition

BDL baseline diversion limit under the Basin Plan

Cap The Murray–Darling Basin Ministerial Council Cap on Diversions

EFRG Environmental Flows Reference Group

EWA environmental water allowance

ECA environmental contingency allowance

IQQM Integrated Quantity and Quality Model

LTAAEL long-term average annual extraction limit

MDB Murray–Darling Basin

MDBA Murray–Darling Basin Authority

MDBSY Project Murray–Darling Basin Sustainable Yields Project

PBP pre-Basin Plan

SDL sustainable diversion limit

WM Act Water Management Act 2000

WRP water resource plan

WSP water sharing plan


NSW Department of Industry | INT18/192694 | 1

Introduction 1The Murray–Darling Basin Plan 2012, established under the Water Act 2007, defines the maximum

limit of consumptive diversions at valley as well as basin scale. Water resource plans (WRPs) are being developed for each valley to meet Basin Plan requirements. A significant element of the WRP is that the allowable long-term average annual diversions have been set as the sustainable diversion limit (SDL). The SDL scenario is also a component of the method for determining the permitted take. The SDL is calculated using the baseline diversion limit (BDL), which is the long-term average annual diversion calculated over the period 1895-2009 that was allowable under state water planning law prior to when the Basin Plan was formulated. The SDL is the BDL minus a fixed recovery target.

These long-term average annual diversions are estimated using IQQM or Source software models of the river system. These models estimate a range of water balance components such as streamflow and diversions based on climatically derived water availability, levels of water resource development, and water sharing policies.

An estimate of BDL for the Lachlan Surface Water Source (Error! Reference source not found.) by MDBA was published in Schedule 3 of the 2012 Basin Plan. The MDBA’s Lachlan BDL estimate included the diversions from Belubula Regulated River system, a tributary in the north-east of the Lachlan Valley

This estimates has since been revised by NSW. The changes in the Lachlan Regulated River system were principally based on improved flow calibration and revisions of components of the water sharing plan (WSP) based on actual rather than assumed operation. These improvements are reported in a related technical report (NSW Department of Industry, 2018d). Improvements were made separately to the Belubula Regulated River system, which in this case meant a re-building of the actual model as described in (NSW Department of Industry, 2018a). These changes were combined to provide an updated estimate of the BDL for the Lachlan Surface Water Source.

This change in the revised BDL estimate has resulted in a commensurate revised SDL that the Lachlan WRP needs to comply with. The Lachlan WRP has been developed with water sharing arrangements and rules informed by the results of a range of modelled scenarios which have been presented and discussed by the stakeholder advisory panel (SAP).



Figure 1-1. Lachlan River Catchment

1.1 The Sustainable Diversion Limit scenario The SDL scenario is the model configured with the development conditions that currently exist and proposed management arrangements that will be in place for the WRP period to 2029. This includes development conditions such as: public infrastructure, areas developed for irrigation, and the capacity of water users to extract and store water on farm, as well as management arrangements such as the distribution and usage patterns of entitlement holders, the crop area planting decisions of irrigation enterprises, and operation of storages to supply consumptive and environmental water.

The SDL scenario demonstrates that the WRP would be SDL compliant over the historical reference period 1895 to 2009 in response to clause 10.10 of the Basin Plan. This report describes the development of the SDL scenario, and should be read in conjunction with other reports including the PBP and BDL scenario reports (NSW Department of Industry, 2018d, 2018e).

1.2 Purpose of report This report is intended primarily for MDBA to fulfil the Basin Plan requirements for WRP accreditation. This report describes how the SDL Scenario was developed, and documents the key features of the scenario.

The technical content of this report is kept to only that necessary to meet the intent. The general development and calibration of the model is described in the IQQM Cap Implementation Summary Report (Hameed et al, 2002).



Model development 2

2.1 Pre-2009 The Lachlan IQQM was initially developed in the late-1990s using an early version of the IQQM software. The capability of the model to estimate annual and long-term average diversions was established by the independent review processes under Cap governance arrangements. Cap model audits by MDBC were required to assess the following aspects:

the accuracy of the model to predict annual total diversions;

method to establish levels of development, and their incorporation into the models;

method to adjust water use for climatic variation;

the capability of the model to simulate long-term diversions; and

robustness of the model to simulate outside the calibration period.

The calibration and set up of the model is described in the Lachlan Valley Cap report (Hameed et al.; 2002). The model was accredited for Cap Auditing in 2002 based on recommendations by the Independent reviewer (Bewsher Consulting, 2002). The Independent Auditor concluded the model to be sufficiently robust and unbiased, and it could be used to simulate annual totals and long-term average annual diversions. A further review of the model was undertaken as part of the MDB Sustainable Yields Project, and to establish its fitness-for-purpose for use for MDBA modelling for the Basin Plan (Podger et al., 2010).

The Lachlan IQQM was subsequently to help formulate the Lachlan Water Sharing Plan (WSP), including establishing a Long Term Average Annual Extraction Limit (LTAAEL), also known as the Plan Limit. A separate analysis was undertaken to establish a Plan Limit for the Belubula WSP.

2.2 Revisions to model

2.2.1 Post-2009

Changes were made to the Lachlan Plan Limit scenario model to better represent elements of the WSP. These include upgrades to the accounting system, improved estimates of timing and volumes of water needed for operational aspects of the WSP such as replenishment flows, environmental water usages, etc (NSW Department of Industry, 2018d)

The WSP sets aside allowances in Wyangala Dam to provide for replenishment flows in the Lower Lachlan River for Willandra, Merrowie and Merrimajeel-Muggabah Creeks. In practice, WaterNSW replenish these flows with releases from Wyangala Dam with much lower volumes than the WSP allowed for. This was done by using unregulated and surplus flows during most years, and releases from Wyangala Dam only during dry years. The modelled replenishment behaviour was revised using data supplied by WaterNSW.

Software limitations at the time the Lachlan model was supplied to MDBA did not allow the simulation of continuous accounting. The software was upgraded in 2016 to allow for continuous accounting as it applies in the Lachlan Valley. The IQQM software only allows for a single accounting system. For this reason, the Belubula Regulated River system Plan Limit scenario model with annual accounting, was modelled separately, and the simulated Belubula end of system (EoS) flows used as an inflow to the Lachlan Plan Limit model.

In 2018, a new model using the Source software modelling platform was developed for the Belubula Regulated River system to support the development of WRP. Lachlan scenario models were updated to include the updated simulated end of the system flows from the equivalent Belubula SDL scenario models (NSW Department of Industry, 2018c). The changes to the Lachlan and Belubula regulated river system models resulted in changes to the estimate of the Plan Limit.



As the Plan Limit scenarios generally correspond to the Basin Plan BDL scenario, the estimates of BDL have changed compared with those published in the Basin Plan.

2.2.2 Difference of SDL from PBP

A Pre-Basin Plan (PBP) scenario model was also developed for both Lachlan and Belubula regulated river systems. These scenarios include updated estimates of farm development, and any changes in management arrangements, including on-farm management, compared to those included in the BDL scenario. The PBP scenario formed the basis for all proposed rule change scenarios considered in the WRP development process.

The rule changes were primarily in the Belubula regulated river system as follows:

10 ML/d Belubula end of system flow suspension trigger based on flow conditions in Flyers Creek

removal of the without debit provision in the current WSP for General Security (GS) license holders but with storage trigger to allow access to uncontrolled flows an average of 15% of the time

reduction in the GS account limit from 130% to 110%

Details of the Belubula WRP package scenario model are reported in the Belubula Regulated River System- Proposed WRP Scenario Model (NSW Department of Industry, October 2018).



Valley SDL number 3The surface water SDL for the Lachlan water resource plan area is defined by the Basin Plan as the BDL minus 48 GL/year of local reduction.

The BDL is based on the sum of the modelled diversions, un-modelled watercourse diversions and interceptions. Schedule 3 of the BP states Lachlan BDL to be 625.7 GL/year, and consists of the following components:

Regulated river diversions: 287 GL/year (including Belubula)

Unregulated rivers take (excluding take under basic rights): 16 GL/year

Take by runoff dams: 287 GL/year

Take by commercial plantations: 29 GL/year

The required Valley SDL is calculated as Updated BDL minus Required Recovery. Assuming no further changes in the shared reduction target, the Lachlan SDL is 577.7 GL/year, calculated as (625.7 minus 48).



Results and demonstration of SDL 4compliance

4.1 Long-term simulation results

Table 1 shows the average annual usage for different components of the models discussed. The results are limited to General Security, and High-Security, Conveyance, Local Water Utility, and Stock and Domestic diversions.

Table 1. Comparison of modelled results from updated BDL and SDL scenarios (1985–2009)

Usage category

Scenario

Updated BDL SDL

(long-term average usage in GL//year

General Security 249.6 176.8

Lachlan 249.6 176.6

Belubula 6.0 4.0

JIL Conveyance 14.1 16.1

High Security 10.4 10.5

Town Water Supply 8.0 8.0

Stock and Domestic 5.6 5.3

Held Environmental Water

General Security 49.0

High Security 2.5

Total regulated systems 293.7 272.1

Unmodelled (MDBA estimates)

- Unregulated 16 16

- Runoff dams 287 287

- Commercial plantations 29 29

TOTAL 625.7 604.1

4.2 Description of representation of HEW As of September 2018 NSW and Commonwealth Held Environmental Water (HEW) portfolio in the Lachlan consists of the following entitlements:

123,492 ML of General Security, all of which were recovered through irrigation licence buybacks

2,728 ML of High Security, which were recovered through irrigation licence buybacks.

Because very little is known regarding how exactly HEW is going to be used, the use of assumed demand behaviours for the HEW portfolio would introduce material risk that the resulting scenario



could show third-party impacts or benefits that are unrealistic. To avoid distortion of the scenario outcomes that may alter decisions made around other rules and options being considered, the HEW portfolio has been modelled as a consumptive use that assumes an irrigation demand pattern.

Based on this modelled representation of HEW, a deemed use can be estimated through application of the latest LTDLE factors. Results and calculation process are shown below. Estimate on current water recovery in the Lachlan is also presented in Table 2.

Table 2. Estimates of NSW and Commonwealth HEW via LTDLE Factors

Usage category

LTDLE

factor

NSW and Commonwealth HEW

Entitlement (shares) SDL deemed use (GL/y)

Calculation → [1] [2] [3]=[2] x [1]

Domestic and Stock 0.402 0 0

Local Water Utility 0.530 0 0

High Security 0.927 2,728 2,530

Conveyance 0.834 0 0

General Security 0.396 123,492 48,923

TOTAL 126,220 51,453

4.3 SDL Compliance and current water recovery The estimate of current recovery in Lachlan is 51.4 GL, which is 3.4 GL more than the target of 48 GL. Based on figures in Table 1 and Table 2, the expected long-term average diversion over the period 1895 to 2009 is 552.8 GL (604.2 minus 51.4 GL), which is about 24.9 GL lower than required SDL of 577.7 GL discussed in Section 3.

4.3.1 Calculation of permitted take

Section 10.10 of the Basin Plan requires the WRP for each SDL resource unit to set out the method for determining the maximum quantity of water that the plan permits to be taken for consumptive use in each water year after 30/06/2019. For the Lachlan, this method consists of running SDL scenario model over the year of SDL compliance audit and assessing simulated take against actual take.



Table 3. Calculation of annual permitted take using SDL model

Water take Nodes/Value # of

Nodes

IQQM

Output

variable

Post-

processing Comment

Modelled

High Security

(HS)

Node type

3.2 with HS

labels

6 2 none

Demand with restriction

based on the storage

volume. Restriction not

applied.

Stock &

Domestic

Node type

3.2 with

S&D labels

4 2 none




applied.

Lachlan General

Security (GS)

Node type

8.0 22 1 none GS irrigation

Belubula

General Security n/a n/a n/a n.a

Refer to Belubula WRP

report Table xxx

Local Water

Utility

Node type

3.2 with

TWS labels

6 2 none




applied.

Conveyance

Node type

3.0 node#

322

1 2 none JIL conveyance

Environmental

GS

Node type

8.0 node#

321

1 1 none GS Env with LicVol of 111

GL

New GS

Environmental

Node type

3.8 node#

319

1 2 none 'New GS Env Lic' ds Lake

Brewster with 12 GL Lic vol

Environmental

HS

a) Node type

3.2 node#

375

1 2 none Label “Env HS Irr”

Unmodelled (as estimated by MDBA)

Unregulated1 16.0 n/a n/a

Adopt

estimate

Schedule 3 (13b) of BP

2012

Basic Rights n/a n/a n/a As above Yet to be estimated

Runoff dams 287 n/a n/a As above Schedule 3 (13d&e) of BP

2012

Commercial

plantations 29 n/a n/a As above Schedule 3 (13f) of BP 2012

Total Sum all

values

1 Excludes extraction under Basic Rights



SDL key model parameters 5Table contains key configuration information for the SDL scenario.

Table 4. SDL infrastructure and development parameters

Items Description

General

System File Name LachP069.SQQ (updated 2018 Belubula SDL)

IQQM Version developed in 7.91.8 Rev3013

Available Simulation Period 01/01/1895-30/06/2015

Water Year July to June

Valley Development Levels

Maximum Crop area

Crop Mix

Licence Volume

Crop Planting Decision

2012/13

2012/13

2012/13

2012/13-2014/15

Catchment Information

Storages modelled

Wyangala

Inactive storage (GL)

Full supply volume (GL)

Lake Cargelligo



Brewster Weir



Lake Brewster



1

1217

15

45

0

15

16

160

Inflows (GL/y for 1/7/1895-30/6/2009)

u/s Wyangala

Lachlan gauged tribs

Belubula

719

227

136

Entitlements

General Security (Shares)

Upper Lachlan Irrigation

Lower Lachlan Irrigation

Environment ds Whealbah

Downstream Lake-Brewster

285,099

184,210

111,492

12,000

High Security (Shares)



Items Description

Irrigation

Environment

Town Water Supply

Stock and Domestic

JIL Conveyance

24,952

2,728

15,545

12,245

17,950

Irrigation Development

Maximum irrigable area (ha) 62,546

On-farm storage capacity (GL) Nil

Pump capacity (ML/d) 25,000

Accounting System

Type

Debiting type

Maximum balance (%)

Maximum use of entitlement

Continuous

Water use

200

100

Resource Assessment

Maximum Use 100%

Storage Operations

Lake Cargelligo Filled using surplus flow and kept at 16 GL in dry years by ordering water from Wyangala

Lake Brewster Filled using surplus flows

Tributary utilisation factors (%)

Boorowa R

Belubula R

Back Ck

100

100

50

In-stream requirements

Maximum caps (ML/y)

Merrowie

Muggabah

Merrimajeel

Willandra

Booberoi

8,000 (June 1 to July 15) of 180 ML/d

4,500(May 1 to June 29) of 75 ML/d

4,500(May 1 to June 29) of 75 ML/d

10,000 (June 15 to Aug 15) of 180 ML/d

12,495 (20 ML/d June to Aug, 60 ML/d

Dec and Jan, 30 ML/d Mar to Apr)

(If unregulated flows don’t reach the thresholds by certain

dates in each creek in each year, the remaining balance is

released towards these creeks after those dates.)

Minimum flow requirements (ML/d)



Items Description

Lachlan R @ Wyangala

Lachlan R @ d/s Brewster Weir

Lachlan R @ Booligal

October to March

April to September

70

20

80

30

Planned Environmental Water

Wyangala Translucency releases When Wyangala cumulative inflow from January 1 becomes

greater than 250 GL, depending upon Wyangala storage

volume, a flow event between 3,500 and 8,000 ML/d can be

maintained at Brewster between 1 June and 30 November.

The total volume of such flows cannot exceed 350 GL in a

water year.

ECA to be made available when the start of

water year allocation is 50%

5 GL/y downstream of Wyangala and 5 GL/y downstream of

Lake Brewster with a daily demand of 83 ML/d from May to

June, September to November

Water Quality allowance Average usage set to 14 GL/y. Currently modelled as

minimum flow ds Wyangala dam of 166 ML/d from January

to April when Lake Brewster is about 67% full on January 1.

It is planned to link this to Dam inflows later on.



References 6Government of Commonwealth of Australia 2007, Water Act (WA) 2007, Canberra, 2010.

https://www.legislation.gov.au/Details/C2007A00137

Department of Infrastructure, Planning and Natural Resources (DIPNR) (2004), Water Sharing Plan for the Lachlan Regulated River Water Source. NSW DIPNR 2004. https://www.legislation.nsw.gov.au/#/view/regulation/2016/365/full

Barma, D., Hughes. D, Powell, S., Wettin, P., Hameed, T., Driver, P., Harris, K, Terrill, P, Packard. P. (2010). Lower Lachlan wetlands scoping study. Final Report Barma Water Resource Consulting Pty Ltd for the NSW Office of Water, May 2010, pp 306.

Bewsher Consulting Pty Ltd (2002). Lachlan River Valley, Independent Audit of Cap Model. Bewsher Consulting Pty Ltd, August 2002, pp 91 .

Hameed, T, McDermott, G, Chowdhury, S and Arranz, P. (2002). Lachlan River Valley; IQQM Cap Implementation Summary Report. CNR, DLWC, pp 92 .

Podger, G.M., Barma, D., Neal, B., Austin, K. and Murrihy, E. (2010). River System Modelling for the Basin Plan Assessment of fitness for purpose. CSIRO: Water for a Healthy Country National Research Flagship, Canberra, December 2010, pp 64.

Murray–Darling Basin Authority (MDBA) 2011, Water Resource Assessments for Without Development and Baseline Conditions Report, MDBA, 2011.

Murray–Darling Basin Authority (MDBA) 2016, NSW BDL based LTDLE factors v20A – 25 May 2018.xlsx, MDBA, 2018.

NSW Department of Industry (2018a). Belubula Regulated River System – Baseline Diversion Limit Scenario Model. Department of Industry Water. October 2018.

NSW Department of Industry (2018b). Belubula Regulated River System – Pre-Basin Plan Scenario Model. Department of Industry Water. October 2018.

NSW Department of Industry (2018c). Belubula Regulated River System – Proposed WRP Scenario Model. Department of Industry Water. October 2018.

NSW Department of Industry (2018d). Lachlan Regulated River System – Baseline Diversion Limit Scenario Model, Department of Industry Water, October 2018.

NSW Department of Industry (2018e). Lachlan Regulated River System – Pre-Basin Plan Scenario Model, Department of Industry Water, October 2018.

https://www.legislation.gov.au/Details/C2007A00137

https://www.legislation.nsw.gov.au/#/view/regulation/2016/365/full

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