Water resources - Allocation and Use - Victoria

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Victoria

The baseline year for the Audit is the 1996/97 agricultural year starting on the 1st April and ending on 31st of March. For water use the data was compiled for the period 1 July 1996 to 30 June 1997 (water calendar year). When it is necessary to collect information for more than one year, the data collected must cover that year or, alternatively, appropriately adjusted to provide a best estimate for that year.

For water use data States and Territories were requested to provide a 5 yearly average value based on the 1996/97 year. Use figures were adjusted in areas where, due to climatic conditions, the water use was not considered to be 'average'.

Climate in 1996/97

During 1996 there was a transition from the weak large-scale climate controls to a strong El Ni?o condition after March 1997. This resulted in a drying over a large part of southern and eastern Australia. From July until September 1996 Victoria had unusually cold and wet weather. The remainder of the southern half of Australia was also wet for three months. Significant areas in south-west Queensland, western and central New South Wales, South Australia, western Victoria, and southern Western Australia had rainfall totals within the highest 10% on record.

During the summer of 1996-97, there was a very active monsoonal season in the tropical zones in western Australia and the Northern Territory. However, this finished abruptly and early, as El Ni?o developed rapidly in autumn 1997. From October 1996 very dry conditions prevailed over most of Victoria, the grain belts of South Australia and north-east Tasmania. Areas of southern Victoria through to south-east South Australia had the driest October to June period on record.

May 1997 brought rain to southern Australia and average to above average rain to parts of Queensland. There was some relief to farmers from the dry and hot conditions over southern Australia in early 1997. In parts of southern Victoria and south-east South Australia the driest October to June period was reported. (ABS Water Account, 2000)

Climate in 1983/84 (Water Review 85)

Water use in any particular year is affected by weather conditions. For much of Australia, the period, July 1983 to June 1984, was equivalent to a normal year in which water use was about average. In south-east Australia, however, abnormal weather patterns were experienced. In general, rainfall totals throughout Victoria were high during the first half of the year but were lower than average in the second half. These weather conditions, along with a continuing sensitivity to water use following the 1982/83 drought, had a marked effect on water usage. Although the 1982/83 drought that affected most of Victoria was broken by above-average rains early in the year, water restrictions in many urban areas were not lifted until much later in the year. Urban water use was therefore less than average, due both to the heavy rains and to the continuance of water restrictions.

The above-average rains in the first half of 1983-84 greatly reduced irrigation demands, and by mid-season virtually unrestricted supplies of water were made available to farmers (for example, 200% of water rights in the Goulburn-Murray Irrigation District). The drier conditions in the latter half of the year somewhat compensated for this, but total usage for the year was generally far less than average.

Rural usage was also less than average, again due to the early wet conditions and sensitivity about excessive water use following the 1982-83 drought. (DPIE, 1987).

Note:

Note: The change in water use volume from 1985 to 1996 does not always reflect factors affecting consumption patterns and volumes such as population growth, industry or land-use change or operational improvements. The observed difference may partly be attributed to differences in the approach and assumptions used to estimate water use within the river basin.

Total water use for the Snowy River Basin and East Gippsland Basin has not been reported as these volumes were not available for the NSW component of the basin.

A direct comparison between data reported for 1985 and 1996 cannot be made for the Murray Riverina Basin due to a change in the boundary definition of the Basin. For this current assessment the Murray Riverina Basin has been defined as the regulated stretch of the Murray River extending from Lake Hume to the South Australian border. In 1985 the Murray Riverina Basin is defined as an area on the New South Wales side of the Murray River, extending from Hume Dam to a point just upstream of the confluence with the Murrumbidgee River.

Chart of Proportion of total water use by consumptive classes

Basin Name	Use in 1983-84 (GL /yr)	Use in 1996-97 (GL /yr)	% Change
VIC	4,053	5,166	27
Avoca River	36	40	12
Barwon River	12	33	182
Broken River	473	898	90
Bunyip River	6	151	2,458
Campaspe River	198	442	124
East Gippsland	2	1	-63
Glenelg River	4	4	19
Goulburn River	500	920	84
Hopkins River	12	14	15
Kiewa River	11	15	38
Lake Corangamite	6	5	-20
Latrobe River	81	195	141
Loddon River	804	1,176	46
Mallee	452	363	-20
Maribyrnong River	4	23	486
Millicent Coast	8	4	-53
Mitchell River	9	12	39
Moorabool River	3	23	953
Murray-Riverina	1,408	1,914	36
Otway Coast	4	13	276
Ovens River	20	40	103
Portland Coast	2	2	-3
Snowy River	337	3	-99
South Gippsland	10	12	32
Tambo River	3	3	6
Thomson River	140	226	62
Upper Murray River	9	25	186
Werribee River	24	83	246
Wimmera - Avon Rivers	45	131	191
Yarra River	8	327	4,099

Note: The total surface water use reported for each river basin does not include the water consumption of the eleven major cities. The data for cities and river basins are reported in the State totals.

How are the surface water resources used and allocated in Victoria?

Chart of Proportion of surface water use by consumptive classes

Table: Surface water diversion and allocation 1996-97

Basin/SWMA Name	Allocation (GL/yr)	Diversion (GL/yr)	Diversion: Allocation (%)
Victoria	6,284	5,980	0
Avoca River	4	4	100
Avon River	8	8	100
Barwon River	46	41	88
Broken River	32	32	100
Bunyip River	47	11	23
Campaspe River	121	121	100
East Gippsland (Vic)	2	1	42
Glenelg River (Vic)	73	72	99
Goulburn River	1,943	1,943	100
Hopkins River	11	7	67
Kiewa River	9	9	100
Lake Corangamite	1	1	100
Latrobe River	222	161	72
Loddon River	109	109	100
Maribyrnong River	10	8	71
Mid-Murray River (Hume to SA Border) (Vic)	1,639	1,639	100
Millicent Coast (Vic)	1	1	100
Mitchell River (Vic)	19	12	62
Mitta Mitta River	835	835	100
Moorabool River	46	17	36
Otway Coast	27	20	74
Ovens River	26	26	100
Portland Coast	2	2	100
Snowy River (Vic)	6	3	39
South Gippsland	22	12	54
Tambo River	7	3	41
Thomson-Macalister Rivers	428	342	80
Upper Murray River (Vic)	4	4	100
Werribee River	33	33	98
Wimmera - Avon Rivers	95	95	100
Yarra River	467	421	90

Note: Allocation is not based on 1999-2000 estimates; Diversion based on five-yearly average 1996-97.

Note: In the table above, the total surface water use reported for each river basin does not include the water consumption of the eleven major cities. The data for cities are reported in the State totals. The volume diverted is the total volume of the SWMA's surface water resources diverted for use both within the management area and for export to other management area. The figures reported for the Mitta Mitta River and in the State totals includes the diversion and allocation to NSW of 814 GL/yr.

The total volume of surface water allocated for use in Victoria is 5469 GL, which represents 80% of the sustainable yield of 6862 GL for the State. An additional 814 GL is allocated for commitments to NSW. The total allocation of the State's resources represents 92% of the sustainable yield.

At present, approximately 5166 GL of surface water is used in Victoria annually. This represents 75% of the sustainable yield of the resource and 82% of the currently developed yield.

Water use in Victoria is dominated by irrigation, which uses 78%, or about, 4019 GL, of total extracted water on average each year. Urban and industrial use accounts for a further 17%, or 861 GL, of total use (approx. 60% of which occurs in Melbourne) and rural supplies for 5%, or about 286 GL. The urban use component comprises around 47% domestic use, 34% industrial/commercial, 6% for other uses such as parks and gardens, and 13% losses.

Most of the land under irrigation is located north of the Great Dividing Range and is supplied from the Goulburn and Murray Rivers. Approximately 40% of irrigation water is devoted to the production of pasture, which is used primarily to feed animals that provide meat and dairy products.

Please note: The tables set out below detailing Level 1 and Level 2 water use categories. The sum of the Level 2 water use volumes will not necessarily equal the total Level 1 water use volumes. This is primarily due to lack of more detailed water use data. However, where Level 2 use = Level 1 use then blank cells in the table does not indicate water use unaccounted for in these categories.

Table: Surface water use in Victoria 1996-97

Basin/SWMA Name	Irrigation (GL/yr)	Rural (GL/yr)	Urban / Industrial (GL/yr)	Total (GL/yr)	In-situ (GL/yr)
Victoria	4,021	286	860	5,166	no data
Avoca River	20	16	5	40	no data
Avon River	47	1	1	48	no data
Barwon River	4	1	29	33	no data
Broken River	857	32	9	898	no data
Bunyip River	5	1	146	151	no data
Campaspe River	420	17	6	442	no data
East Gippsland (Vic)	1	1	1	1	no data
Glenelg River (Vic)	2	1	3	4	no data
Goulburn River	860	35	27	920	no data
Hopkins River	7	1	8	14	no data
Kiewa River	7	2	7	15	no data
Lake Corangamite	1	1	4	5	no data
Latrobe River	48	2	146	195	no data
Loddon River	1,102	46	29	1,176	no data
Mallee (Vic)	319	32	13	363	no data
Maribyrnong River	2	1	21	23	no data
Millicent Coast (Vic)	0	1	1	1	no data
Mitchell River (Vic)	9	1	3	12	no data
Mitta Mitta River	20	1	1	21	no data
Moorabool River	1	3	20	23	no data
Otway Coast	3	6	4	13	no data
Ovens River	27	4	10	40	no data
Portland Coast	2	1	0	2	no data
Snowy River (Vic)	2	1	1	3	no data
South Gippsland	5	2	7	12	no data
Tambo River	2	1	2	3	no data
Thomson-Macalister Rivers	174	4	2	179	no data
Upper Murray River (Vic)	3	1	1	4	no data
Werribee River	25	1	58	83	no data
Wimmera - Avon Rivers	28	87	16	131	no data
Yarra River	32	no data	295	327	no data

Map of surface water use for irrigation in 1996

Map of areas where surface water allocation is greater than sustainable yield

How are Victoria's groundwater resources used and allocated?

The total groundwater use is estimated to be 622 GL/a, which includes 510 GL/a in the GMUs and a further 112 GL/a in the UAs. The predominant use in the UAs is for irrigation (60%), stock and domestic (20%), mine dewatering and urban use (16%) and in-situ uses (4%).

Based on the data for 1996/97, approximately 80% of the total allocated volume for groundwater is being used, with 160 GL of allocated groundwater not being used. However, more recent estimates indicate that this gap between allocation and use is closing, reflecting both an increase in demand for water and the decreasing availability of surface water supplies in many locations.

"GMU"=Groundwater Management Unit "UA"=Unallocated Area

Province	Use in 1983-84 (GL /yr)	Use in 1996-97 (GL /yr)	% change	Current Alloc (GL/yr)	Current Use : Alloc (%)	GMU / UA
Victoria	198	622	215	1	7,072	GMU
Victoria	198	622	215	67	100	UA
Gippsland	1	183	167	187	90	GMU
Gippsland	1	183	167	19	0	UA
Lachlan	1	225	179	538	34	GMU
Lachlan	1	225	179	71	0	UA
Murray	1	764	731	1,607	46	GMU
Murray	1	764	731	27	0	UA
Otway Highlands	no data	1	no data	no data	no data	GMU
Otway Highlands	no data	1	no data	1	0	UA
Otways	1	218	186	336	56	GMU
Otways	1	218	186	33	0	UA
Port Phillip	1	21	14	18	76	GMU
Port Phillip	1	21	14	9	0	UA
Westernport	no data	13	10	12	86	GMU
Westernport	no data	13	10	3	0	UA

Map of total groundwater use in 1996 by province

Chart of total groundwater use by use class

Table: Groundwater use in Victoria 1996-97

Province	Irrigation (GL/yr)	Rural (GL/yr)	Urban / industry (GL/yr)	In-situ (GL/yr)	Total (GL/yr)	SY (GL/yr)
Victoria	431	55	128	11	622	3,658
Gippsland	93	9	83		187	629
Lachlan	141	50	35		226	1,491
Murray	722	27	16		770	2,388
Otway Highlands	no data	1	no data		1	86
Otways	175	17	27		218	1,817
Port Phillip	12	4	6		22	216
Westernport	9	2	3		13	39

Map of groundwater use for irrigation in 1996 by groundwater province

Surface and groundwater interactions

Current Status of Conjunctive Management in Victoria

Groundwater is the minor player in the supply of the State's water, with some 11% of total water use being drawn from groundwater resources. However, it is now being increasingly recognised that, in many areas, groundwater substantially contributes to the baseflow of surface streams, and that groundwater use can impact upon the availability of surface water resources (and vice versa).

The Water Act 1989 prescribes in considerable detail the setting up of Groundwater Supply Protection Areas (GSPAs), and the development of Groundwater Management Plans for these areas. On the other hand, it is silent on the question of Streamflow Management Plans (SMPs), which are developed in an informal arrangement between NRE and the rural water authorities. It is recognised that part of the function of SMPs is to apportion the baseflow between consumptive use and the environment.

Ideally, where there is a significant interaction between surface and groundwater systems, there should be some integration of groundwater and surface water planning and management processes.

The only conjunctive management of surface and groundwater resources currently in place in Victoria is in relation to 'on-farm' water allocations in some locations, where total water use cannot exceed a set allocated volume, regardless of the source of the water. Goulburn Murray Water currently has such a policy in place in some irrigation districts, particularly in those areas covered by salinity management plans, where infiltration of water to the groundwater can cause rising water tables and, subsequently, increased land salinisation. The implementation of the policy is still in its infancy and the data required to enforce this policy is currently not readily available (pers. comm. D Morrison (GMW) October 2000).

While current SYs for some GMUs take into consideration baseflows to rivers and lakes, and have reduced SYs to allow for the maintenance of these surface water flows, these allowances have been made on the basis of very limited information. The impact of groundwater use on river baseflow needs to be monitored to determine whether the assumptions that have been made are correct, and what management actions are required in order to ensure that surface water resources are not impacted upon by the extraction of groundwater resources.

Impediments to Conjunctive Management of Surface and Groundwater Resources

Impediments to the conjunctive management of surface and groundwater resources are:

insufficient data on groundwater levels and use;
in most cases there is not satisfactory scientific quantification of surface environmental flow requirements;
inadequate understanding of the significance of climate variability (in particular floods) in influencing recharge;
the need to establish appropriate conceptual models of how groundwater and surface water systems interact, on which to base the development of principles for the joint management of the resources; for example:
the extent to which decreases in watertable level affect stream baseflow is virtually universally unquantified, along with the levels at which rivers begin recharging aquifers, such as during high flow periods;
little is known about the distance from a stream in which groundwater extractions should be limited to avoid adverse impacts on baseflow, or under what climatic conditions use in the stream and/or groundwater should be limited; and
the lack of a formal statutory mechanism to allow for the joint management of surface water and groundwater.

Priorities for Conjunctive Management

Rural water authorities have identified streams that they consider require investigation as a matter of priority because of their potential interaction with groundwater systems. Monitoring is required in these situations to determine the connection between surface water and groundwater.

For the purposes of the Audit, a further assessment was made of the priorities for considering conjunctive management of surface and groundwater resources. The listed priorities are based on the categorisations of the various GMUs and SWMAs relative to current use, and on the degree of physical connection between surface water and groundwater systems. Of the 63 GMUs in Victoria, 44 are physically connected to surface water resources.

Having prioritised GMUs and SWMAs in relation to the need for conjunctive management, the next steps would involve specifying and prioritising particular river reaches and the aquifers connected to those particular reaches. Information currently available indicates that most aquifers are connected either in part to a river reach, or have variable connection along a stream's length. More detailed information would be required prior to any conjunctive use policy or management process being put in place. This would include information on the physical processes and connections between surface water and groundwater systems, on the impacts that high use of groundwater or surface water has on the other resource, and an estimate of the joint 'sustainable yield' for the combined systems. As each case differs from the next, management strategies would need to be tailored to particular situations.

Further information

Victoria Water Resources Assessment 2000 Report
Victoria Water Resources Assessment 2000 Technical Report
Link to data available for download on the:

Link to the Map Maker to make a map using this information.

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