River Murray Operations
Joseph Davis
LMW Growers Conference - 20 October 2020 Outline
• State Sharing • River Murray System Resources • Capacity and shortfall Issue
20 October 2020 20 October 2020 Inflow trends
Inflows 2019/20 ~ 3,810 GL 3rd consecutive dry year Storage Trends
20 October 2020 System Inflows
• Inflows for the 2019-20 water year were ~3,760 GL (88% Annual Exceedance Probability)
• For the first four months of the 2020-21 water year Murray System inflows were ~2,690 GL (69% AEP)
• Catchments have fluctuated between dry and wet since August, smaller rain events ‘prime’ catchments for larger flow responses when catchments are wet
• Flow to SA were unregulated from June 27 to 25 September.
20 October 2020 Storages and system conditions and storages
Storages continuing to fill as we enter the key inflow periods for the River Murray System
Dartmouth 58% - 2,240 GL •Transfers remain at the minimum rate – ‘’riparian’ flows near 200 ML/day
Hume 72% - 2,180 GL •Releases at minimums for 4 months, now delivering operational and environmental demands since September Total active storage is ~4,850 GL Menindee 27% - 470 GL •Remains in NSW control, small environmental delivery increased downstream release to 410 ML/d
Lake Victoria 94% - 640 GL • Unregulated flows have ended and Lake Vic assisting in meeting SA demands
Lake Alexandrina – Average five day level 0.88 m AHD Barrage releases increasing in October to 11,300 ML/d as unregulated flows have reached the end of the system
20 October 2020 Bulk water shares : End Sep 2020
20 October 2020 Capacity and shortfall
• Concern of shortfall risk since the mid 1990s • Millennium drought saw focus move away from capacity to water availability • Since 2012-13 increased focus on capacity issues with the change in crop types and location • Risks • Reduced capacity at the Barmah choke • Impacts on the Lower Goulburn River • Climate Change • Perceptions • Increased water use downstream of the Choke • Environmental Flows downstream of the Choke • MDBA heading up intergovernmental investigation into capacity and shortfall Area of horticultural crops (2003-2018) 70,000
60,000
50,000
40,000
30,000
plantings (Ha) plantings 20,000 Area of Horticultural of Horticultural Area 10,000
0 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 Victoria South Australia New South Wales
Source: Irrigated crop area data for the Lower Murray-Darling 2003 to 2018 www.mdba.gov.au/sites/default/files/pubs/irrigated-crop-area-data-for-the-lower-murray-darling-2003-to-2018.pdf (accessed on 12 August 2020) Water use in summer
IVT January-April Environmental water and cons. trade to SA 2000 Use minus IVT SA Entitlement Order
1500
1000
Useage (GL) Useage 500
0
-500
1993/94 1994/95 1995/96 1996/97 1997/98 1998/99 1999/00 2000/01 2001/02 2002/03 2003/04 2004/05 2005/06 2006/07 2007/08 2008/09 2009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16 2016/17 2017/18 2018/19
Source: HARC (2020) Review of historical use of water: Barmah to South Australian border https://www.mdba.gov.au/sites/default/files/pubs/review%20of%20historical%20use%20of%20water%20barmah%20to%20south%20australia.pdf Climate change
Reduced inflows 1895 – 2000 Increases risk of water availability risk
Increased temperatures
Heatwaves more intense Increase the risk of delivery shortfall Increase conveyance
2000 – 2020
Source - Interim Inspector-General of Murray–Darling Basin Water Resources 2020, Impact of lower inflows on state shares under the Murray–Darling Basin Agreement, Canberra Environmental Water Holdings
Murrumbidgee
Lower 655 GL 2209 GL SA Murray Darling 93 35 226 543 GL GL GL GL Murray US Barmah 438 GL 1639 GL 577 1193 GL GL
Murray DS Barmah
545 Held Environmental Water 1278 GL Sustainable Diversion Limit GL Goulburn Barmah Choke Capacity
• Trade restriction in place Capacity downstream of • Has been since 2007 Yarrawonga (ML/day) (enforced 2014) 1980’s ~11,500 • Slowly losing transfer capacity 2003 ~10,300 Currently ~ 9,500 • So what is going on • current thinking is that sand has (is) moving into the Choke reach reducing capacity and causing the river banks to move (erode) • Interactions are complex – geomorphic & hydrologic • Major focus over the next period, however no simple answers • Lifting constraints - separates environmental and consumptive demand • Bypass options – very expensive – may move the problem to the next reach
20 October 2020 • Sources of sediment
• Landuse change • Gold mining • Land clearing • River management • Desnagging • Regulation – Hume and Yarrawonga
The evidence indicates the sand is a result of European settlement
20 October 2020 Land clearing & Gold mining
Beechworth and Mitta Mitta gold mining Sand movement - Preliminary results Managing shortfall risk
• MDBA • River operator, manages releases from storage, transfers between storages • Operates to the MDB Agreement and direction of States through Basin Official Committee (BOC) • Forecast demands based on state advice • States • Manage entitlements and allocations • Control all works licences (rate of extraction) • Collate data and provide advice to MDBA on expected use • Manage all trade of water – allocation and entitlement • Define and enforce any restriction in their jurisdiction 20 October 2020 Shortfall Response plan
MDBA advising States State States implement (WLWG, RMOC, BOC) Applying mitigating measures Ministers restrictions Exploring options for reinstating delivery capacity
• Strategic use of storages below the Choke • By-passing the Choke • Detailed investigation being proposed • What this means for the choke trading restriction – key issue • Managing Sediment within the Choke • Riparian Works within the reach between Yarrawonga and Torrumbarry • Potential relaxing capacity constraints • greater than 15,000 ML/day downstream of Yarrawonga for environmental flow Office locations Adelaide Griffith Albury-Wodonga Mildura Canberra Murray Bridge Goondiwindi Toowoomba
mdba.gov.au 1800 630 114 [email protected]