Lachlan River Operations 2019

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Lachlan River Operations 2020- 21

River Operations Stakeholder Consultation Committee (ROSCCo) 24 Nov 2020

1 Recent Rainfall 1 Aug to 31 Oct 20

Nov 20

WaterNSW 2 Rainfall Deciles

1 Aug to 31 Oct 20

WaterNSW 3 Drought Inflow Comparison

Wyangala Drought Inflows for 40 Months Starting in August

Aug 1979 - Jul 1982 Aug 2002 - Jul 2005 Aug 2007 - Jul 2010 Aug 2017 - Oct 2020 (39 months) Aug 1944 - Jul 1947 1000

900

800

700

600

500

400 CumulativeInflows GL in 300

200

100

0 0 5 10 15 20 25 30 35 40 45 No of Months 4 Current Storage Status

• Wyangala: as at 23 Nov 20 • Storage Volume: 795,206 ML • Storage Percent: 65.3% • System Inflows since 1July20 – 31Oct 20: 856,017 ML • System Inflows in Nov 20 – 24 Nov 20: 74,000 ML(54 Dam + 20 GL d/s tribs)

• Lake Cargelligo: • Storage Volume: 24,391 ML • Storage Percent: 60%

• Lake Brewster: • Storage Volume: 49,500 ML • Storage Percent: 34%

5 Wyangala Dam Operations

Lachlan River Operation 2020-21

Dam Inflows (Monthly) Dam Release Extractive Orders_Upper Lachlan Dam Level 8000 100%

7000 55.5GL 83GL 411.5GL 42.5GL

6000 75% 54GL

Trans release 5000

4000 50%

Flows in ML/d in Flows Dam Level in % in Level Dam 3000

2000 25%

1000

0 0% 01-Jul-20 01-Aug-20 01-Sep-20 01-Oct-20 01-Nov-20 01-Dec-20 01-Jan-21 01-Feb-21 01-Mar-21 01-Apr-21 01-May-21 01-Jun-21

6 Water Availability in 2020-21 Water Allocation Statement Nov 2020 • Towns and S&D – 100% AWD • High Security – 100% AWD • Conveyance Licence – 15,200 ML • General Security – 38% AWD and All account balance available • S&D replenishment flows – to be delivered in 2021 • ECA – zero (require additional 21% AWD to GS to get allocated, 16 + 38 + 21 = 75%) • WQA – 10 GL assessed as likely use in 2020-21

7 Water Account Summary 31 October 2020 - Lachlan

Sum of Sum of Allocation Allocation Sum of Share Sum of Account Sum of Available Sum of AWD Sum of Assignments Assignments Row Labels Component Balance Water Vol Carryover In In Out Sum of Usage DOMESTIC AND STOCK 10,954 10,521 10,365 10,954 - 8 - - 425 DOMESTIC AND STOCK [DOMESTIC] 176 174 174 176 - - - 2 DOMESTIC AND STOCK [STOCK] 1,599 1,590 1,590 1,599 - 0 - - 9 LOCAL WATER UTILITY 15,545 14,732 14,597 15,545 - - - 813 REGULATED RIVER (CONVEYANCE) 17,911 14,718 14,718 15,221 107 - - 610 REGULATED RIVER (GS Irri) 469,309 185,836 182,990 150,177 22,509 7,833 20,532 8,778 REGULATED RIVER (GS Env) 123,492 18,801 18,801 39,518 13,728 2,739 43,347 22,157 REGULATED RIVER (HS Env) 24,952 33,323 33,225 24,952 - 26 17,681 4,816 4,468 REGULATED RIVER (HS Irri) 2,728 16,327 16,327 2,728 - 41,575 1,133 26,844 Grand Total 666,667 296,021 292,787 260,869 36,309 69,828 69,828 64,104

8 Resource Availability/Distribution end of October 2020

WaterNSW 9 Translucent Flow Event 2020 Translucent Flow Event - 2020 6000

Translucent Flows at Willandra weir 5000 Aug/Sept20

4000

Translucent Flows at Willandra weir Nov20

3000 Flow Flow ML/d Translucent Flows 2000 ceased @Willandra Licenced Env Flows weir to provide smooth recession 1000

16-Oct-20 02-Oct-20 04-Oct-20 06-Oct-20 08-Oct-20 10-Oct-20 12-Oct-20 14-Oct-20 18-Oct-20 20-Oct-20 22-Oct-20 24-Oct-20 26-Oct-20 28-Oct-20 30-Oct-20

18-Sep-20 02-Sep-20 04-Sep-20 06-Sep-20 08-Sep-20 10-Sep-20 12-Sep-20 14-Sep-20 16-Sep-20 20-Sep-20 22-Sep-20 24-Sep-20 26-Sep-20 28-Sep-20 30-Sep-20

21-Aug-20 17-Aug-20 19-Aug-20 23-Aug-20 25-Aug-20 27-Aug-20 29-Aug-20 31-Aug-20

01-Nov-20 03-Nov-20 05-Nov-20 07-Nov-20 09-Nov-20 11-Nov-20 13-Nov-20 15-Nov-20 17-Nov-20 19-Nov-20 21-Nov-20 23-Nov-20 25-Nov-20 27-Nov-20 29-Nov-20

Flows @ Willandra Weir Flows arriving Willandra OT

Translucent Accounted at Dam Lake Releases 6 GL of under delivery at flows = 179 GL Brewster Releases the dam 29 Oct – 2 Nov Aug/Sept 2020 129.5 GL 0 10 GL released as recession 12 – 21 Nov 36.7 GL 36.8 GL 4.3 GL from 6 Nov 22 – 23 Nov 6.8 GL 0 3.5 GL 10 Airspace Operations

11 Climate Outlook

Dec 20 to Feb 21 Dec 20 to Feb 21

12 Wyangala Airspace Assessment in 2017

13 GS Allocation Reset due to Storage Spill

14 Likely AWD due to GS Reset from storage spill

15 Planned Outage

• Lake Cargelligo Inlet Regulator – Rehabilitation work date TBA – Dry work site with block bank in u/s

• Wyangala Dam low level Ring Follower Valve and Hydro Electric Power Station guard valve – planned outage for winter 2021, TBA

• Lake Brewster main embankment southern face protection – repair work in progress, no planned outage

16 Determine what % of remaining GS balances is deliverable – from 1 December in 2020-21 – Belubula River -Only an indicative calculation

• Dam holding = 11,400 ML (32% of FSL)

• Dam Inflow = 100 ML (min. inflow stats Oct – June)

• Useful Tribs Inflow = 2,600 ML

• Total = 14,100 ML

• GS available use = 5,000 ML (77% of GS balances, in 2019-20 = 46%)

• HS likely use = 1,095 ML

• S&D likely use = 0 ML

• Less Transmission Losses = 1,200 ML

• Less Operational Surpluses = 800 ML

• Less Dam net evaporation = 900 ML

• End of System Flows = 2,100 ML • Total likely Distribution = 11,095 ML

• Potential storage volume on 30 June 21 = 3,005 ML (8%)

WaterNSW 17 Discussions and Recommendations

• Potential irrigation water use in 2020-21 and carryover into 2021-22 • Potential environmental water use in 2020- 21 • S&D replenishment flows in 2021 • Water utilities – progress on projects funded to source Groundwater supplies https://www.waternsw.com.au/waterinsights/ • WaterInsights water-insights

18 To keep updated

Visit the website at: waternsw.com.au/drought For information on the Macquarie Valley including water availability reports and drought reports go to: waternsw.com.au/supply/drought-information/regional- nsw/macquarie-valley

Call us on: 1300 662 077

Subscribe at: waternsw.com.au/subscribe For weekly customer drought updates and more information

WaterNSW 19 Thank you for joining us today

WaterNSW 20 Translucent Flow Rules

• Translucent flows are triggered when 250 GL inflows into WY dam from 1 January

• Inflows to Wyangala + trib flows to produce flows at Brewster weir min 4,000 ML/d (WY <50%) or 3,500 ML/d (WY >50%)

• Rate of release from the dam not exceeding the daily inflows and to target max flows at Brewster Weir on a sliding scale based on WY dam % to 8,000 ML/d

• Translucent Flows stop when surplus flows at Brewster Weir from 1 June exceed 350 GL

• Water orders are released on top of translucent flows

• Releases from the lakes may be substituted for all or part of the translucent flows released from WY if dam releases are likely to cause flooding

• Excess flows above max target flow arriving Brewster Weir are stored in the lakes or used to meet other demands

• Translucent period at the dam 15 May to 15 November

21 Modified Translucent Flow Rules – 2020-21 (to utilise LB Volume)

• Deliver majority or all storage releases required for the translucent release from Lake Brewster and Lake Cargelligo

• Nil or only minimal release from Wyangala Dam

• Rate of release from the storage is calculated as provided for under WSP rule

• Releases from Lakes are subject to no detrimental water quality in the lakes

22 23 24 Extreme event stages

Stage Water quantity Water quality

Stage 1 Raw water can be treated Continue to deliver water as normal with usual methods Normal management

Operational surface water measures to Stage 2 conserve supplies Minor adjustments to treat raw water Emerging water shortage Potential or actual impacts on groundwater

Restrictions on water for: Major adjustments are Stage 3 ∙ High priority licences needed to treat raw water Severe water shortage ∙ General security licences Unacceptable groundwater impacts Water only available for critical human Not possible to treat raw needs water with standard Stage 4 processes Restrictions on all licences Critical water shortage Raw water likely to remain Risk to long term availability of the untreatable over the longer groundwater resources term