Murray and Lower Darling Operations Plan. September 2018

Transcription

1 ` Murray and Lower Darling Operations Plan September 2018

2 Contents 1. Highlights Dam storage Dartmouth storage Hume Dam storage Lake Victoria storage Lake Menindee storage Supplementary access Commentary Water availability /2019 water availability for NSW Murray as of 31 August Resource assessment Prognosis for the current assessment Water Balance Notes: Significance of this resource assessment Resource assessment process Rainfall month rainfall month rainfall Inflows Dartmouth Dam Inflows Hume Dam inflows Downstream tributary inflows Operational loss Operational losses to date in NSW Murray Storage forecast Dartmouth Dam storage forecast Hume Dam storage forecast Lake Victoria storage forecast Menindee Lakes storage forecast Next 3 months scenario from the BOM forecast Outage planning... 23

3 1. Highlights Storage Status End August Dartmouth Dam was 89% (3,439 GL) of active capacity and falling. The NSW share was 1,250 GL. Release through August averaged approximately 2,700 ML/day. o Dartmouth to Hume transfers commence mid-august. Hume Dam was 51% (1,542 GL) of active capacity and rising. The NSW share was 555 GL. Release through August averaged approximately 4,500 ML/d. Lake Victoria was 50% (333 GL) of active capacity and steady. The NSW share was 114 GL. Predicted Release Patterns Releases from Dartmouth Dam have now increased, with the increasing need for transfer of water to Hume Dam. If conditions remain dry transfers will continue throughout Spring and Summer to ensure supply from Hume Dam can be maintained. Releases from Hume Dam have now increased to meet the irrigation / environmental demands and to transfer water to Lake Victoria. Releases downstream of Yarrawonga Weir are currently 13,000 ML/day for operational pruposes, and could increase to 15,000 ML/day in the period ahead, depending on demands and Lake Victoria transfer requirements. The higher flows are required to ensure sufficient water is transferred to Lake Victoria in advance of expected system demands over summer and into autumn. The diversions to the Edward River system are being maximized, and this is expected to continue throughout Summer. The use of MIL escapes is now possible, and will be used where possible to bypass water around the Barmah Choke area. However, escape use will be limited by the capacity constraints of the Edward River downstream of Stevens Weir, and the Wakool River system. Flows downstream of Stevens Weir have increased to channel capacity and are likely to remain at this level through Spring and Summer if dry conditions persist. Operating Conditions The 17th September Water Allocation Statement confirmed the general security allocation of zero, while Available Water Determinations (AWD) are 100% for towns and 97% for high security. Average carryover into is 31% of general security share components. Potential Blue Green Algae issues. o Hume Dam: Results for August show a minor diatom bloom occurring across the storage with a moderate presence of benign cyanobacteria. A minor detection of Nostocaceae sp. was noted at Ebden but otherwise not potentially toxic cyanobacteria were detected. Storage remains at green alert.

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5 2. Dam storage 2.1 Dartmouth storage 100% Dartmouth Dam storage 90% 80% 70% 60% 50% 40% 30% 20% 10% 2014/ / / / /19 0% Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun From the above figure it can be seen that Dartmouth Dam was under 80% at the start of the last water year and it is now close to 90% of active capacity. Transfers from Dartmouth to Hume totaled approximately 155GL in 2017/18, with almost 120 GL of transfers occurring in the first 2 months of 2018/19. The storage has remained steady since January, but is forecast to be drawn down substantially this year if dry conditions persist.

6 2.2 Hume Dam storage 100% Hume Dam storage 90% 80% 70% 60% 50% 40% 30% 20% 10% 2014/ / / / /19 0% Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun From the above figure it can be seen that Hume Dam was around 70% at the start of the last water year and it is slightly over 50% of active capacity. The storage was drawn down by releases for deliveries, and has not received any significant inflows due to a dry Autumn-Winter. The increase in storage volume since May 2018, is attributed to releases from the Snowy Hydro Scheme, with delivery of the required annual release. Further to this transfers from Dartmouth to Hume commenced in mid-august 2018, also boosting the storage level, but not resulting in any new resource for NSW.

7 2.3 Lake Victoria storage 110% Lake Victoria storage 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 2014/ / / / /19 0% Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun From the above figure it can be seen that Lake Victoria was under 65% at the start of the last water year and it is now just under 50% of active capacity. The storage was drawn down throughout summer and autumn by releases to meet system demands. The dry autumn and winter has provided no significant inflows from tributaries downstream of Hume Dam. The storage falling throughout August is an unusual occurrence and is due to the dry conditions and higher than expected demands and losses. Operations are currently focusing on transfers to Lake Victoria from Hume Dam to ensure the storage holds sufficient volume to meet peak summer demands.

8 2.4 Lake Menindee storage Menindee Lakes storage 100% 90% 2014/ / / / /19 80% 70% 60% 50% 40% 30% 20% 10% 0% Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun From the above figure it can be seen that Lake Menindee was around 45% at the start of the last water year and it is now just under 10% of active capacity. The storage was drawn down by releases for deliveries. The storage reached the 480 GL trigger in mid-december, at which time releases were reduce to the minimum required to maintain system connectivity, the first drought management action in this sequence. Wilcannia has recorded just 14 GL since that time. 3. Supplementary access 3.1 Commentary There have not been any supplementary events in the NSW Murray or Lower Darling since the start of the 2018/19 water year.

9 4. Water availability /2019 water availability for NSW Murray as of 31 August 2018 Licence category Sum of share component Sum of carry over in Sum of AWD volume Sum of trade In Sum of trade out Sum of usage Sum of account balance Domestic and Stock 13, , ,350 11,398 Domestic and Stock 1, , ,052 [Domestic] Domestic and Stock 2, , ,943 [Stock] Local Water Utility 33, , ,486 31,611 Regulated River 330, ,994 38, ,389 32,450 (CONVEYANCE) Regulated River 1,674, , ,028 83,083 98, ,439 (General Security) Regulated River 189, ,017 11,912 50,026 6, ,908 (High Security) Regulated River (High Security) [Community and Education] Regulated River (High Security) [Research] Regulated River 3, , (High Security) [Town Water Supply] Grand Total 2,247, , , , , , ,774 General security available water determination Date Allocation (ML/Share) Total (%) 1 July % NSW Murray Allocation Licence category Date of allocation (ML/Share, %) 0.00 / 0% General security 1 July / 97% High security 1 July / 100% Domestic and stock 1 July / 100% Local water utilities 1 July / 27% Conveyance 3 September 2018

10 No General Security AWD has been announced since 1 July In this current water year, 0% Available Water Determination (AWD) has been announced on 17 September 2018 for General Security (GS). For High Security water users the AWD is 97% while for Domestic and Stock as well as Local Water Utilities users the AWD is 100%. For conveyance the AWD is 27%. Average carryover into is 31% of general security share components. Further general security AWD s are possible throughout the year. The sum of account balance refers the amount of water available to the account of the users after trades and usage.

11 4.2 Resource assessment Source: data/assets/pdf_file/0007/170359/was-murray pdf Source: data/assets/pdf_file/0007/170359/was-murray pdf

12 4.3 Prognosis for the current assessment Murray and Lower Darling Operations Plan - September 2018 Forecast General Security allocation (per cent) using Dry Tercile # (Any carryover water can be added to these indicative allocations) Potential Inflow Conditions 1 Nov 2018 General Security Allocation 99 chances in 100 (extreme) (99%) chances in 10 (very dry) (90%)^ 0^^ 5 3 chances in 4 (dry) (75%) 0^^ 14 1 chance in 2 (mean) (50%) chance in 4 (wet) (25%) ** 1 Nov 2019 General Security Allocation # Outlook modelling using inflow data for the driest one-third of years only and GS carryover of 31% ^ June to August 2018 conditions have been tracking at 89% AEP ^^ Conveyance estimated to be at least 130 GL at 1 Nov 2018 in the 90% and 165 GL in the 75% scenarios ** Borrow from B-M Allowance is fully repaid 4.4 Water Balance Notes (1) Supply Distribution and Remaining Commitments the distribution of supply and commitments is being provided on a monthly basis. The volumes in the categories shown are only those relating to NSW s share of the resource, at the end of the preceding month. The categories include the following: Water in storage: Volumes in the dams at the end of the previous month. (Excludes water in storage unavailable to NSW under the water sharing arrangements of the Murray Darling Basin Agreement). Estimated use since 1 July: Estimated NSW usage to-date, reconciled periodically with hydrographic updates (meter readings). Forecast inflows: NSW s share of forecast inflows into the River Murray System based on assumed extremely dry future conditions (includes Snowy Hydro s guaranteed inflows for the water year). Murrumbidgee IVT: Total Murrumbidgee system water bought by Murray system users that is yet to be delivered, as reported in the Murrumbidgee IVT account balance. A negative IVT balance will appear as a commitment of NSW Murray water to the Murrumbidgee, until trades between the two valleys brings the IVT balance up to nil.

13 Evaporation: Water set aside for evaporation for the remainder of the year. This reduces as the year progresses. River losses upstream of SA: Water budgeted for transmission losses from the River Murray system upstream of the South Australian border for the remainder of the year. Generally reduces as the water year progresses. SA non-dilution entitlement: Water to supply South Australia s entitlement flow, as required under the Murray Darling Basin (MDB) Agreement. Reduces as water year progresses. SA dilution flow: Water to provide South Australia s dilution component of flow, as required under the MDB Agreement. Reduces as the year progresses, unless Additional Dilution Flow (ADF) is triggered. MDB Agreement required reserves: Includes conveyance reserve and minimum reserve to be set aside for use in the next water year, as required by the MDB Agreement in clause 102D and 103, respectively. Water available for allocation: NSW s bulk share of the resource that can be assigned to NSW Murray entitlement holders based on the water sharing plan. This volume includes entitlement holder carryover. The allocation of this volume is provided in the above table and pie chart Significance of this resource assessment The current resource assessment at 17 September 2018 indicates that there is no general security AWD announcement in this month Resource assessment process The resource assessment is the process of calculating how much water is available based on the rules of the Water Sharing Plan (WSP). This is done at the end of the month and when any significant inflow event happens. The above resource assessment table is for the planning horizon from 17 September 2018 to 30 August 2020.

14 5. Rainfall month rainfall The above figures show that the last 6-month total rainfall is within the below average to very much below average for the majority of the NSW Murray catchment.

15 month rainfall The above figures show that the last 12-month total rainfall is in the range predominately in the below average range, with only the ranges experiencing average conditions.

16 Inflow Volume (GL) Inflow Volume (GL) Murray and Lower Darling Operations Plan - September Inflows 6.1 Dartmouth Dam Inflows Dartmouth Dam - 6 month inflows/statistical inflows 99 percentile 75 percentile 50 percentile 25 percentile Actual Inflow Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Inflows are below rainfall trends over the past 6 month period. Actual inflow for the 6 months is 194GL just below the 90 th percentile inflows (213GL): while the minimum is 92GL. Dartmouth Dam - 12 month inflows/statistical inflows percentile 75 percentile 50 percentile 25 percentile Actual Inflow Inflows are consistent with rainfall trends over the past 12 month period. Actual inflow for the 12 months is 541GL just below 75 th percentile inflows (603GL): while the minimum is 166GL.

17 Inflow Volume (GL) Inflow Volume (GL) Murray and Lower Darling Operations Plan - September Hume Dam inflows Hume Dam - 6 month inflows/statistical inflows percentile 75 percentile 50 percentile 25 percentile Actual Inflow Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Inflows are consistent with rainfall trends over the past 6 month period. Actual inflow for the 6 months is 320GL which is between the 90 th and 95 th percentile inflows ( GL): while the minimum is 106GL. Hume Dam - 12 month inflows/statistical inflows percentile 75 percentile 50 percentile 25 percentile Actual Inflow Inflows are consistent with rainfall trends over the past 12 month period. Actual inflow for the 12 months is 971GL just below 90 th percentile inflows (1,050GL): while the minimum is 124GL.

18 Inflow Volume (GL) Inflow Volume (GL) Murray and Lower Darling Operations Plan - September Downstream tributary inflows Total tribs - 6 month inflows/statistical inflows 99 percentile 75 percentile 50 percentile 25 percentile Actual Inflow Mar-18 Apr-18 May-18 Jun-18 Jul-18 Aug-18 Inflows are better than rainfall trends over the past 6 month period. Actual inflow for the 6 months is 1,186GL which is slightly better than the 75 th percentile inflows (1,076GL): while the minimum is 300GL Total tribs - 12 month inflows/statistical inflows 99 percentile 75 percentile 50 percentile 25 percentile Actual Inflow Inflows are better than rainfall trends over the past 12 month period. Actual inflow for the 12 months is 2,777GL slightly better than 75 th percentile inflows (2,266GL): while the minimum is 575GL.

19 Operational Loss/Sales (%) Murray and Lower Darling Operations Plan - September Operational loss 7.1 Operational losses to date in NSW Murray Operational loss is water above that which could reasonably be expected to pass end-of-thesystem gauge as the last point on Murray River being supplied with regulated flow (dam releases and controlled tributary inflows not supplementary flows). 10% NSW Murray - water delivery operational loss vs sales cumulative % 8% 6% Target below 5% 4% 2% 0% The table below shows that year to date sales and environmental delivery, including end of system flow requirement (324 GL) and operational loss (0GL). NSW Murray Cumulative totals Sales + Operational Actual Target environmental delivery surplus Jul % 5% Jul-Aug % 5%

20 Jul-16 Oct-16 Jan-17 Apr-17 Jul-17 Oct-17 Jan-18 Apr-18 Jul-18 Oct-18 Jan-19 Apr-19 Storage Capacity (%) Murray and Lower Darling Operations Plan - September Storage forecast 8.1 Dartmouth Dam storage forecast 110% Dartmouth Dam - forecast storage capacity 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% Actual Extreme dry scenario (99%) Dry scenario (90%) Near average scenario (50%) Wet scenario (25%) 0% Forecast was completed at end May, The storage forecast will be reviewed in the coming months by MDBA. The above figure demonstrates provides a range of scenarios that may occur at Dartmouth Dam under different inflow conditions through to June The chart demonstrates that only under near average or higher inflow conditions would the dam be likely to fill. Under the dry scenarios, Dartmouth will be drawn on to transfer water to Hume Dam to ensure summer demands can be met. As the forecast was complete in May, we can see that actual conditions to date this year have seen more water remain in Dartmouth Dam than forecast in the Extreme dry scenario. However, we are tracking below the dry scenario at Dartmouth.

21 Jul-16 Oct-16 Jan-17 Apr-17 Jul-17 Oct-17 Jan-18 Apr-18 Jul-18 Oct-18 Jan-19 Apr-19 Storage Capacity (%) 8.2 Hume Dam storage forecast Murray and Lower Darling Operations Plan - September % Hume Dam - forecast storage capacity 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Actual Extreme dry scenario (99%) Dry scenario (90%) Near average scenario (50%) Wet scenario (25%) Forecast was completed at end May, The storage forecast will be reviewed in the coming months by MDBA. The above figure demonstrates provides a range of scenarios that may occur at Hume Dam under different inflow conditions through to June The chart demonstrates that only under a wet inflow scenario would the dam be likely to fill, essential there is only a 1 in 4 chance of this occurring. Under all scenarios, Hume Dam will be drawn on to meet system demands. Under the driest scenarios the storage could fall to as low as 10%. In essence the chart shows that there is a 10 % chance of this occurring, and a 90% of the storage ending the season higher than this. As the forecast was complete in May, we can see that actual conditions to date this year have seen more water remain in Hume Dam than forecast in the dry scenario.

22 Jul-16 Oct-16 Jan-17 Apr-17 Jul-17 Oct-17 Jan-18 Apr-18 Jul-18 Oct-18 Jan-19 Apr-19 Storage Capacity (%) 8.3 Lake Victoria storage forecast Murray and Lower Darling Operations Plan - September % Lake Victoria - forecast storage capacity 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Actual Extreme dry scenario (99%) Dry scenario (90%) Near average scenario (50%) Wet scenario (25%) Forecast was completed at end May, The storage forecast will be reviewed in the coming months by MDBA. The above figure demonstrates provides a range of scenarios that may occur at Lake Victoria under different inflow conditions through to June The chart demonstrates that at least near average conditions or better are required to fill the storage. Under all scenarios, Lake Victoria will be drawn on to meet system demands. Under all scenarios, the storage is likely to meet the Lake Victoria operating strategy and of May storage target. As the forecast was complete in May, we can see that actual conditions to date this year have been below the extreme dry scenario. This is due to higher than expected demands through late July and August. This trend is of concern and Lake Victoria transfers from Hume Dam have commenced in August.

23 8.4 Menindee Lakes storage forecast Murray and Lower Darling Operations Plan - September 2018 A storage forecast is provided in the Lower Darling Operations Plan Next 3 months scenario from the BOM forecast 9. Outage planning Item Time Description Hume Dam N/A None Mulwala Weir N/A None Torrumbarry Weir N/A None Stevens Weir Winter Painting of the super structure. Works planned to commence in the winter drawdown to minimize the risk of impact to consumptive demands. However the duration may extend into late Winter or Spring. This risk is being considered in the planning of the outage and will be managed through the design of the maintenance process. Euston Weir N/A None Wentworth Weir N/A None Reviewed by Vladimir Stojnic on 19 September Approved by Vincent Kelly on 19 September