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2. Wimmera- Mallee Water Resource Plan area Water flowing from Wimmera river to Lake Hindmarsh, 22 September 2016 by Kathryn Walker at Wimmera CMA. Department of Environment, Land, Water and Planning The Basin Plan establishes long-term average sustainable diversion limits (SDLs) for 110 surface and groundwater SDL resource units that are located within WRP areas. BASIN The following water resource plan areas and water resources are identified: PLAN 10.02(1) Wimmera-Mallee (surface water) water resource plan area and all surface water resources in that area as described under section 3.05(n) of the Basin Plan; and Wimmera-Mallee (groundwater) water resource plan area and all groundwater resources in that area as described by 3.06(p) of the Basin Plan. The surface water and groundwater plan areas differ slightly, with the groundwater area extending to the Murray River in the north while the surface water area excludes the irrigation districts supplied from the Murray River and a strip of land along the Victorian side of Murray River. The Wimmera-Mallee WRP areas for surface and groundwater are shown in Figure 1 and Figure 2 respectively. 2.1 Surface water boundaries The surface water component of the Wimmera-Mallee WRP area includes parts of three basins in Division IV, Murray-Darling Basin, of the Australian Water Resources Council (AWRC) Drainage Basins (Auslig 2001) as shown in (Figure 1): • Basin 15 – Wimmera-Avon • Basin 8 – Avoca • Basin 14 – Mallee. The Wimmera-Avon rivers surface water basin is not connected to the Murray River. The Avoca basin is infrequently connected to the Murray River via the Avoca floodway that connects with the Kerang Lakes during floods. The Mallee basin is a semi-arid zone that has no perennial streams, localised run off during exceptionally wet conditions and no surface water diversions. The Wimmera-Mallee WRP surface water area benefits from inter-basin water transfers from the Glenelg basin in the south, the Murray River in the north and the Goulburn system in the east. It also transfers water south to the Hopkins basin to supply towns such as Ararat. 24 | Part 2. Wimmera Mallee Water Resource Plan Wimmera Mallee Water Resource Plan Department of Environment, Land, Water and Planning Figure 1 – Wimmera-Mallee WRP area for surface water and corresponding AWRC drainage divisions and river basins AWRC drainage divisions and river basins Wimmera-Mallee WRP surface water area MILDURA M U R R A B Y O R IV U E R N R E D V A I R R Y Y E A X R Hattah C R L U U M DES THE MALLEE Ouyen LAKE SWAN HILL TYRRELL (Direl) LAKE AVOCA T ALBACUTYA Y R (Nalbagatja) R E L LAKE LAKE L C COORONG R LASCELLES EE K Y A R R I WIMMERA-AVON A M B Birchip I LAKE A C Wycheproof HINDMARSH Brim K W C IM R M E E E K R LAKE A Charlton R Warracknabeal BULOKE LODDON I V A Nhill E (Wurunibial) V R Donald O C A Dimboola R IV ER MILLICENT AV (Y a R O n I ER g COAST C N RIV a H St Arnaud n HORSHAM TAYLORS g A R ) LAKE D M S Natimuk A PINE O C NORT N RIVER K O LAKE E N N Glenorchy TOOLONDO C Z R IE Navarre E R RESERVOIR E I K V LAKE LONSDALE ER F Y Stawell Avoca A N WHITE S LAKE LAKE C R LAKE WARTOOK E E FYANS K GLENELG ROCKLANDS LAKE RESERVOIR BELLFIELD ARARAT HOPKINS Wimmera Mallee Water Resource Plan Part 2. | 25 Department of Environment, Land, Water and Planning 2.2 Groundwater boundaries Under the Murray-Darling Basin Plan, groundwater resources in the Wimmera Mallee Water Resource Plan area (Figure 2) are divided into three SDL units: • Wimmera-Mallee Sedimentary Plain SDL unit – all groundwater from the land surface to 200 metres below the surface or 50 metres below the base of the Tertiary sediments, whichever is deeper • Wimmera-Mallee Deep SDL unit– all groundwater excluding groundwater in the Wimmera-Mallee Highlands and Wimmera-Mallee Sedimentary Plain SDL units • Wimmera-Mallee Highlands SDL unit – all groundwater in the outcropping Paleozoic rocks (or the in situ weathered horizon within 5 metres of the surface) from the land surface to 200 metres below the surface. These definitions may change under MDBA Basin Plan amendments being considered. The Victorian Groundwater Management Framework consists of management units that are made up of groundwater catchments, groundwater management areas and water supply protection areas (collectively known as groundwater management units). The Murray Basin is divided into the Wimmera-Mallee Catchment and Avoca Catchment managed by Grampians Wimmera Mallee Water, and the Goulburn-Murray Catchment managed by Goulburn-Murray Water. The Wimmera-Mallee WRP area consists of the Wimmera-Mallee Groundwater Catchment and Avoca Groundwater Catchment. The groundwater resources in both catchments are mostly saline located from the northern Grampians (Gariwerd) to the Murray River. It should be noted that that the groundwater SDL does not include groundwater take within the West Wimmera GMA because the groundwater resources in the West Wimmera GMA have been excluded from the water resources of the Murray-Darling Basin under the Water Regulations 2008 (Cth) (available at https://www.legislation.gov.au). This is due to the groundwater resources within the West Wimmera GMA being only remotely hydrologically connected to the Murray River and disconnected to surface ecosystems in the Murray-Darling Basin. 26 | Part 2. Wimmera Mallee Water Resource Plan Wimmera Mallee Water Resource Plan Department of Environment, Land, Water and Planning Figure 2 – Victorian groundwater management units and corresponding Wimmera-Mallee WRP area as at 1 February 2017 Groundwater catchment Groundwater management area MILDURA Water supply protection area Wimmera-mallee WRP groundwater area M U R R B A O Y R U IV R N E E R D V A I R R Y Y E A X R C R Hattah L U U M DES THE (20km either side of the border) (20km either side of South Australia/ Victoria Border Zone Zone Border Victoria South Australia/ MURRAYVILLE Ouyen LAKE SWAN HILL TYRRELL (Direl) AVOCA T Y LAKE R R ALBACUTYA E LAKE L (Nalbagatja) LAKE L C LASCELLES R COORONG EE Y K A R Wycheproof R I A M B Birchip LAKE I A HINDMARSH C WIMMERA K Brim C - MALLEE W R IM E M E LAKE WEST K E WIMMERA R BULOKE A Charlton R Warracknabeal I V Nhill E (Wurunibial) R Donald A V Dimboola O C A RI VE St Arnaud R R (Y I N a C AVO RIV E n H Natimuk R g A a HORSHAM TAYLORS n R g M D LAKE S ) A O C N R NORT RIVE K TOOLONDO O N E PINE N Glenorchy RESERVOIR C LAKE ZI R E Navarre E RIV E E K R F Avoca WHITE Y Stawell A LAKE N S LAKE LONSDALE LAKE C R LAKE WARTOOK E E FYANS LAKE K GLENELG ROCKLANDS RESERVOIR BELLFIELD ARARAT Wimmera Mallee Water Resource Plan Part 2. | 27 Department of Environment, Land, Water and Planning Figure 3 shows a simplified stratigraphy of the Wimmera-Mallee: Sedimentary Plains SDL groundwater unit in the northern part of the Wimmera-Mallee WRP area (Mallee CMA, 2013). In this SDL, there are three main aquifers (which are extensive and continue north and west into South Australia): • Pliocene Sands Aquifer (also referred to as the Parilla Sands Aquifer) • Tertiary Limestone Aquifer (also referred to as the Murray Group Limestone Aquifer) • Tertiary Confined Sands Aquifer MURRAYVILLE UNDERBOOL OUYEN MANANGATANG West Blanchetown Clay Woorinen East Aquitard Formation MURRAY RIVER Parilla Sands Aquifer (saline) Bookpurnong Formation (clay) Geera clay Murray Group (Duddo) Limestone Aquifer SAVIC BORDER clay) Renmark Group ation ( Ettrick Form Aquifer Not to scale Figure 3 – Simplified stratigraphy of the Wimmera-Mallee sedimentary SDL in northern part of the Wimmera-Mallee WRP area. Groundwater in this part of the Wimmera-Mallee: Sedimentary Plain SDL unit is predominantly saline and unsuitable for agriculture or human use. The exception to this is the Murray Group Limestone aquifer, a confined aquifer found in the western part of the Wimmera-Mallee. However, usable groundwater is limited to the confined resources along the Victoria-South Australia border. The Wimmera-Mallee: Highlands SDL unit comprises the fractured rock aquifers and shallow alluvial deposits along waterways. 28 | Part 2. Wimmera Mallee Water Resource Plan Wimmera Mallee Water Resource Plan Department of Environment, Land, Water and Planning Border Groundwaters Agreement – South Australia-Victoria (DEWNR, 2016) Along the South Australian-Victoria border, groundwater is the only reliable water source and there is increasing demand for the use of this resource. It is used for irrigation and for industrial, stock and domestic supplies. Many towns close to the border also rely on groundwater for their public water supply. The resource is shared between both states and in recognition of the need to cooperatively manage these resources the two states entered into the Border Groundwaters Agreement (the Agreement) in 1985. The Agreement was updated in 2005 and is currently under review. The Agreement provides that the available groundwater shall be shared equitably between the two states and applies to all existing and future bores. Bores that extract groundwater for domestic and stock purposes are not covered by the Agreement. The Agreement covers an area that extends 20 kilometres either side of the border from the coast to the River Murray. This area is known as the Designated Area and is divided into 22 management zones with 11 Zones in each state.

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