Murray–Darling Basin
Water resources and systems

The following set of notes provides consolidated reports for each of the water stores and systems within the Murray–Darling Basin (MDB) region during the 2011–12 year. The water stores included in the region are shown in Figure 1.

 

Figure 1  Schematic diagram of the water stores within the MDB region

 

For more information about the region, please refer to the General description section of the Contextual information.

Information on all water flows to and from each water store and system is presented in this note, including between-store flows and transfers that are not presented in the water accounting statements. The between-store flows and transfers that occur in the region are presented in Figure 2.

The numbers on the diagram refer to the line item numbers in the water store notes. For each between-store flow, there are two line item numbers: one refers to flow out of a water store and the other refers to flow into a water store.

 

Figure 2  Schematic diagram of between-store flows that occur within the MDB region: line item numbers are provided next to the flows

 

The between-store flows and transfers (Figure 2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.

A description of the Murray–Darling Basin (MDB) region's surface water resources is provided in the Surface water section of the Contextual information.

Table 1 shows that the total surface water store increased during the 2011–12 year in the MDB region.

 

Table 1  Statement of Water Assets and Water Liabilities for the surface water store for the MDB region as at 30 June 2012

Water assets	Northern Basin		Southern Basin		Whole region
	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)
1 Surface water
1.1 Storages	4,314,709	3,333,324	16,872,487	15,798,138	21,187,196	19,131,462
1.2 Unregulated river	–	–	–	–	–	–
1.3 Regulated river	16,249	19,234	1,309,763	1,287,103	1,326,012	1,306,337
1.4 Lakes and wetlands	0	0	1,811,372	1,925,145	1,811,372	1,925,145
1.5 Inter-region claim on water	0	0	913,776	470,066	913,776	470,066
1.10 Other surface water assets	0	0	19,952	18,131	19,952	18,131
Total surface water assets	4,330,958	3,352,558	20,927,350	19,498,583	25,258,308	22,851,141
5 Water liabilities
5.1 Surface water allocation remaining	2,090,549	1,341,685	4,909,329	5,438,652	6,999,878	6,780,337
5.2 Surface water allocation remaining – urban water system	0	0	0	25	0	25
Total surface water liabilities	2,090,549	1,341,685	4,909,329	5,438,677	6,999,878	6,780,362
Opening net water assets	2,010,873	672,772	14,059,906	6,952,943	16,070,779	7,625,715
Change in net water assets	229,536	1,338,101	1,958,115	7,106,963	2,187,651	8,445,064
Closing net water assets	2,240,409	2,010,873	16,018,021	14,059,906	18,258,430	16,070,779

 

Table 1 includes information only for eight lakes: Dock Lake, Pine Lake, Lake Batyo Catyo, Green Lake, Lake Albert, Lake Alexandrina, Lake Burley Griffin, Lake Ginninderra and Lake Tuggeranong. Volume of water stored in other lakes and wetlands could not be quantified accurately due to a lack of available data.

The location of major storages within the MDB region, and the volume of water, including dead storage, in each storage as a percentage of total storage capacity (% full) at the end of the 2011–12 year, is shown in Figure 3.

Figure 3  Location map of major storages within the MDB region: the % full volume on 30 June 2012 for major storages is also shown

 
The water volume in majority of the storages within the MDB region at the end of the 2011–12 year was more than that at the start (see line item 1.1 Storages). The large increase in surface water storage during the year is primarily attributed to high inflows into the storages during the 2011–12 year. This situation reflects the well above average rainfall conditions observed in the region in the 2011–12 year. Some areas, within the region, recorded their highest annual rainfall on record (see Rainfall in 'Climate overview').

Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the surface water store are provided in Tables 2 and 3, respectively. In addition to flows reported in the water accounting statements, the tables also show flows between the surface water and groundwater stores within the region.

 

Table 2  Statement of Changes in Water Assets and Water Liabilities for the surface water store for the year ended 30 June 2012

Description	Northern Basin		Southern Basin		Whole region
	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)
Water asset increases
9 Surface water increases
9.1 Precipitation on surface water	247,093	226,027	1,401,857	1,899,698	1,648,950	2,125,725
9.2 River inflow to region	0	0	4,547,315	1,840,333	01	01
9.3 Groundwater discharge	35,207	7,058	7,159	8,670	42,366	15,728
9.4 Runoff to surface water	32,492,437	33,913,170	31,090,750	49,069,283	63,583,187	82,982,453
9.5 Point return from irrigation scheme	0	0	198,314	216,917	198,314	216,917
9.6 Overbank flood return to river channel	–	–	–	–	–	–
9.9 Discharge from urban water system	0	0	34,325	34,897	34,325	34,897
9.10 Direct discharge by user	–	–	–	–	–	–
9.15 Increase of inter-region surface water claim on water	0	0	2,560,022	3,137,374	2,560,022	3,137,374
9 Total surface water increases	32,774,737	34,146,255	39,839,742	56,207,172	68,067,1641	88,513,0941
13 Surface water liability decreases
13.1 Adjustment and forfeiture of surface water allocation	165,143	187,573	2,010,884	1,136,827	2,176,027	1,324,400
13.2 Adjustment and forfeiture of surface water allocation – urban water system	30,021	26,606	255,722	262,492	285,743	289,098
13 Total surface water liability decreases	195,164	214,179	2,266,606	1,399,319	2,461,770	1,613,498
Water asset decreases
17 Surface water asset decreases
17.1 Evaporation from surface water	366,255	320,996	2,892,164	2,692,725	3,258,419	3,013,721
17.2 River outflow from the region	4,547,315	1,840,333	9,565,600	12,839,048	9,565,6002	12,839,0482
17.3 Leakage to groundwater	104,977	122,295	244,817	268,210	349,794	390,505
17.4 Leakage to landscape	–	–	–	–	–	–
17.5 Overbank flood spilling	299,151	652,699	0	0	299,151	652,699
17.6 Surface water diversions – other statutory rights	38,066	28,516	30,523	19,135	68,589	47,651
17.7 Entitled diversion on non-allocated surface water to users	1,090,894	1,451,542	523,155	565,240	1,614,049	2,016,782
17.8 Entitled diversion of non-allocated surface water to urban water system	3,567	3,167	6,294	17,421	9,861	20,588
17.10 River and floodplain leakage, evaporation and errors	24,648,167	26,656,458	18,308,972	24,978,289	42,957,139	51,634,747
17.17 Decrease of inter-region surface water claim on water	0	0	625,000	765,817	625,000	765,817
17 Total surface water asset decreases	31,098,392	31,076,006	32,196,525	42,145,885	58,747,6022	71,381,5582
Water liability increases
21 Surface water liability increases
21.1 Surface water allocation announcements	1,599,474	1,904,177	7,412,187	7,839,249	9,011,661	9,743,426
21.2 Surface water allocation announcements – urban system	42,499	42,150	539,521	514,394	582,020	556,544
21 Total surface water liability increases	1,641,973	1,946,327	7,951,708	8,353,643	9,593,681	10,299,970
Balancing item – surface water	0	0	0	0	0	0
Change in net water assets	229,536	1,338,101	1,934,252	7,106,963	2,163,788	8,445,064

1. Please note the volume for the Southern Basin for line item 9.2 'River inflow to region' was eliminated in the whole region.
2. Please note the volume for the NorthernBasin for line item 17.2 'River outflow from the region' was eliminated in the whole region.

 

Table 3  Statement of Water Flows for the surface water store for the year ended 30 June 2012

Description	Northern Basin		Southern Basin		Whole region
	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)
Water inflows
9 Surface water increases
9.1 Precipitation on surface water	247,093	226,027	1,401,857	1,899,698	1,648,950	2,125,725
9.2 River inflow to region	0	0	4,547,315	1,840,333	01	01
9.3 Groundwater discharge	35,207	7,058	7,159	8,670	42,366	15,728
9.4 Runoff to surface water	32,492,437	33,913,170	31,090,750	49,069,283	63,583,187	82,982,453
9.5 Point return from irrigation scheme	0	0	198,314	216,917	198,314	216,917
9.6 Overbank flood return to river channel	–	–	–	–	–	–
9.9 Discharge from urban water system	0	0	34,325	34,897	34,325	34,897
9.10 Direct discharge by user	–	–	–	–	–	–
9.11 Delivery of water under inter-region agreement to surface water	0	0	1,491,312	2,310,491	1,491,312	2,310,491
9 Total surface water increases	32,774,737	34,146,255	38,771,032	55,380,289	66,998,4541	87,686,2111
Water outflows
17 Surface water asset decreases
17.1 Evaporation from surface water	366,255	320,996	2,892,164	2,692,725	3,258,419	3,013,721
17.2 River outflow from the region	4,547,315	1,840,333	9,565,600	12,839,048	9,565,6002	12,839,0482
17.3 Leakage to groundwater	104,977	122,295	244,817	268,210	349,794	390,505
17.4 Leakage to landscape	–	–	–	–	–	–
17.5 Overbank flood spilling	299,151	652,699	0	0	299,151	652,699
17.6 Surface water diversions – other statutory rights	38,066	28,516	30,523	19,135	68,589	47,651
17.7 Entitled diversion on non-allocated surface water to users	1,090,894	1,451,542	523,155	565,240	1,614,049	2,016,782
17.8 Entitled diversion of non-allocated surface water to urban water system	3,567	3,167	6,294	17,421	9,861	20,588
17.10 River and floodplain leakage, evaporation and errors	24,648,167	26,656,458	18,308,972	24,978,289	42,957,139	51,634,747
17.11 Entitled diversion of allocated surface water to users	685,467	507,631	5,930,626	3,513,176	6,616,093	4,020,807
17.12 Entitled diversion of allocated surface water to urban water system	12,478	15,509	283,824	251,875	296,302	267,384
17 Total surface water asset decreases	31,796,337	31,599,146	37,785,975	45,145,119	65,034,9972	74,903,9322
Balancing item – surface water	0	0	0	0	0	0
Opening water storage	3,352,558	805,449	19,028,517	8,793,347	22,381,075	9,598,796
Add/(Less): Change in water storage	978,400	2,547,109	985,057	10,235,170	1,963,457	12,782,279
Closing water storage	4,330,958	3,352,558	20,013,574	19,028,517	24,344,532	22,381,075

1. Please note the volume for the Southern Basin for line item 9.2 'River inflow to region' was eliminated in the whole region.
2. Please note the volume for the NorthernBasin for line item 17.2 'River outflow from the region' was eliminated in the whole region.

 

A schematic diagram representing all the inflows and outflows associated with the surface water store in the MDB region is provided in Figure 4. The numbers in brackets on the diagram refer to the line item numbers in Table 3.

 

Figure 4  Schematic diagram of water inflows and outflows for the surface water store within the MDB region during the 2011–12 year: line item numbers are provided in brackets. Irrigation diversions are included in line items 17.7 and 17.11

 

Allocation diversions, non-allocated diversions, and water abstraction under other statutory rights are the main forms of surface water diversions within the MDB region.

The allocation diversions are associated with a water access entitlement. When an allocation is announced, an obligation (water liability) is created on the surface water to deliver water to the user. The entitlement holder (an individual or water supply organisation, where necessary) then orders the release or delivery of the allocated water and diverts it, which reduces the water liability. Allocation diversions, 6,912,395 ML, account for 80% of all diversions within the region for the 2011–12 year.

Non-allocated diversions are also associated with a water access entitlement, but are primarily unregulated diversions. Other statutory rights for surface water diversions are non-entitled water rights. They may be conferred by jurisdictional water acts or be written in water management plans and include land owner basic rights, riparian rights, Indigenous rights and stock and domestic rights.

The entitlement, allocation announcement and forfeiture for water rights associated with surface water diversion during the 2011–12 year are provided in the Water rights, entitlements, allocations and restrictions note.

Figure 5 compares surface water diversions within the MDB region for the 2010–11 year and the 2011–12 year. Non-allocated diversions have decreased but increased for all other categories compare to diversions made during the 2010–11 year.

 

Figure 5  Graph of surface water diversions from storages within the MDB region during the 2011–12 year and the 2010–11 year comparison

 

The volume of the balancing item represents the volume necessary to reconcile the opening and closing balances of the surface water store with the physical water inflows and outflows (Table 4). Inter-store flows between groundwater and surface water stores were included in calculating balancing volume for the surface water store (these flows were excluded in calculating unaccounted-for difference for the water accounting statements because water accounting statements were prepared considering all stores together on an elimination approach, eliminating inter-store flows).

 

Table 4  Balancing item for the surface water store for the 2011–12 year

Description		Volume (ML)
		Northern Basin	Southern Basin	Whole region
	Opening balance (30 June 2011)	3,352,558	19,028,517	22,381,075
add	Total 9 Surface water inflows	32,774,737	38,771,032	66,998,454
minus	Total 17 Surface water outflows	31,796,337	37,785,975	65,034,997
minus	Closing balance (30 June 2012)	4,330,958	20,013,574	24,344,532
	Balancing item – surface water store	0	0	0

 

The volume of the balancing item for the MDB region should be zero. This is because line item  17.10 River and floodplain leakage, evaporation and errors was calculated applying a water balance approach. Therefore, any balancing volume for the region is included in that line item.

A description of the Murray–Darling Basin (MDB) region's groundwater resources are provided under Groundwater in the 'Physical information' section in the 'Contextual information'.

Information on groundwater assets in the region is shown in Table 5. Long term estimates of volumes for extraction (include volume of supplementary access licence that was available for use in New South Wales in the 2011–12 year) and basic landholder rights are defined as the groundwater assets considered for the region. These assets do not reflect temporal fluctuation of groundwater levels. Therefore, groundwater assets for the region are not responsive to groundwater storage changes resulting from water table fluctuations. As a result, groundwater assets are constant except for administrative changes to long-term estimates of volumes for extraction and landholder rights. Increases to administrative groundwater asset volumes may be the result of the commencement of a water resource plan for a groundwater source area within the basin. Decreases in administrative groundwater asset volume in New South Wales may be a result of the reduction of supplementary access licence volumes as outlined in the relevant water resource plans. Information for asset volumes separated into water table aquifers and underlying aquifers are not available for the region.

 

Table 5  Statement of Water Assets and Water Liabilities for the groundwater store for the MDB region as at 30 June 2012

Water assets	Northern Basin		Southern Basin		Whole region
	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)	Volume at 30 June 2012 (ML)	Volume at 30 June 2011 (ML)
2 Groundwater
2.1 Water Table aquifer	–	–	–	–	–	–
2.2 Underlying aquifers	–	–	–	–	–	–
2.5 Other groundwater assets	1,548,941	440,728	2,464,674	913,498	4,013,615	1,354,226
Total surface water assets	1,548,941	440,728	2,464,674	913,498	4,013,615	1,354,226
6 Water liabilities
6.1 Groundwater allocation remaining	0	0	2,498	2,139	2,498	2,139
6.2 Groundwater allocation remaining – urban water system	0	0	0	0	0	0
Total surface water liabilities	0	0	2,498	2,139	2,498	2,139
Opening net water assets	440,728	368,741	911,359	826,159	1,352,087	1,194,900
Change in net water assets	1,108,213	71,987	1,550,817	85,200	2,659,030	157,187
Closing net water assets	1,548,941	440,728	2,462,176	911,359	4,011,117	1,352,087

– = Data not available

 

Changes in water store

The Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows for the groundwater store are provided in Table 6 and Table 7, respectively. In addition to flows reported in the water accounting statements, the tables also show flows between the surface water and groundwater stores within the region.

 

Table 6  Statement of Changes in Water Assets and Water Liabilities for the groundwater store for the year ended 30 June 2012

Description	Northern Basin		Southern Basin		Whole region
	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)
Water asset increases
10 Groundwater increases
10.1 Groundwater inflow from outside region	0	0	2,797	2,941	2,797	2,941
10.2 Groundwater inflow from outside region at coast	0	0	53	76	53	76
10.3 Recharge from landscape	254,547	260,133	2,878,644	10,012,996	3,133,191	10,273,129
10.4 Recharge from surface water	104,977	122,295	244,817	268,210	349,794	390,505
10.5 Leakage from off-channel water storage	–	–	–	–	–	–
10.6 Leakage from urban water system	–	–	–	–	–	–
10.7 Leakage from irrigation scheme	–	–	–	–	–	–
10.8 Managed aquifer recharge – private user	0	0	2,340	4,158	2,340	4,158
10.13 Other groundwater increases	1,116,554	80,562	1,567,106	91,927	2,683,660	172,489
10 Total groundwater increases	1,476,078	462,990	4,695,757	10,380,308	6,171,835	10,843,298
14 Groundwater liability decreases
14.1 Adjustment and forfeiture of groundwater allocation	385,945	271,847	692,254	608,017	1,078,199	879,864
14.2 Adjustment and forfeiture of groundwater allocation – urban water system	11,874	9,128	5,205	3,292	17,079	12,420
14 Total groundwater liability decreases	397,819	280,975	697,459	611,309	1,095,278	892,284
Water asset decreases
18 Groundwater asset decreases
18.1 Groundwater outflow to outside region	0	0	19	14	19	14
18.2 Groundwater outflow to outside region at coast	0	0	1,551	1,625	1,551	1,625
18.3 Discharge to landscape	7,104	36,992	610,649	200,575	617,753	237,567
18.4 Discharge to surface water	35,207	7,058	7,159	8,670	42,366	15,728
18.7 Groundwater extractions – other statutory rights	48,948	12,858	145,228	36,437	194,176	49,295
18.18 Other groundwater decreases	8,341	8,575	15,930	6,254	24,271	14,829
18 Total groundwater asset decreases	99,600	65,483	780,536	253,575	880,136	319,058
Water liability increases
22 Groundwater liability increases
22.1 Groundwater allocation announcements	634,486	396,879	1,051,042	817,370	1,685,528	1,214,249
22.2 Groundwater allocation announcements – urban system	19,107	18,175	6,886	4,631	25,993	22,806
22 Total groundwater liability increases	653,593	415,054	1,057,928	822,001	1,711,521	1,237,055
Balancing item – groundwater1	12,491	191,441	2,003,935	9,830,841	2,016,426	10,022,282
Change in net water assets	1,108,213	71,987	1,550,817	85,200	2,659,030	157,187

 ¹ See Supporting information of line item 25.1 Unaccounted-for difference for details.

 

Table 7  Statement of Water Flows for the groundwater store for the year ended 30 June 2012

Description	Northern Basin		Southern Basin		Whole region
	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)	2011–12 volume (ML)	2010–11 volume (ML)
Water inflows
10 Groundwater increases
10.1 Groundwater inflow from outside region	0	0	2,797	2,941	2,797	2,941
10.2 Groundwater inflow from outside region at coast	0	0	53	76	53	76
10.3 Recharge from landscape	254,547	260,133	2,878,644	10,012,996	3,133,191	10,273,129
10.4 Recharge from surface water	104,977	122,295	244,817	268,210	349,794	390,505
10.5 Leakage from off-channel water storage	–	–	–	–	–	–
10.6 Leakage from urban water system	–	–	–	–	–	–
10.7 Leakage from irrigation scheme	–	–	–	–	–	–
10.8 Managed aquifer recharge – private user	0	0	2,340	4,158	2,340	4,158
10.13 Other groundwater increases	1,116,554	80,562	1,567,106	91,927	2,683,660	172,489
10 Total groundwater increases	1,476,078	462,990	4,695,757	10,380,308	6,171,835	10,843,298
Water outflows
18 Groundwater asset decreases
18.1 Groundwater outflow to outside region	0	0	19	14	19	14
18.2 Groundwater outflow to outside region at coast	0	0	1,551	1,625	1,551	1,625
18.3 Discharge to landscape	7,104	36,992	610,649	200,575	617,753	237,567
18.4 Discharge to surface water	35,207	7,058	7,159	8,670	42,366	15,728
18.7 Groundwater extractions – other statutory rights	48,948	12,858	145,228	36,437	194,176	49,295
18.11 Entitled extraction of allocated groundwater to users	248,541	125,032	358,429	208,880	606,970	333,912
18.12 Entitled extraction of allocated groundwater to urban water system	7,233	9,047	1,681	1,339	8,914	10,386
18.18 Other groundwater decreases	8,341	8,575	15,930	6,254	24,271	14,829
17 Total surface water asset decreases	355,374	199,562	1,140,646	463,794	1,496,020	663,356
Balancing item – groundwater1	12,491	191,441	2,003,935	9,830,841	2,016,426	10,022,282
Opening water storage	440,728	368,741	913,498	827,825	1,354,226	1,196,566
Add/(Less): Change in water storage	1,108,213	71,987	1,551,176	85,673	2,659,389	157,660
Closing water storage	1,548,941	440,728	2,464,674	913,498	4,013,615	1,354,226

 ¹ See Supporting information of line item 25.1 Unaccounted-for difference for details.

 Allocation extraction and water abstraction under other statutory rights are the main forms of groundwater extractions within the MDB region. The allocation extractions are associated with a water access entitlement.

Allocation extractions reported in line item 18.11 (primarily for non-urban purposes), 606,970 ML, account for 75% of all extractions within the region for the 2011–12 year. Extractions for all three entitlement / right categories showed increase in water extractions compare to 2010–11 extractions.  Increased volume for other statutory rights were primarily due to availability of data from the water sharing plans implemented during the 2011–12 year.

The entitlement, allocation announcement and forfeiture for water rights associated with groundwater extraction during the 2011–12 year are provided in the Water rights, entitlements, allocations and restrictions note.

Balancing item – groundwater store

Table 8  Balancing item for the groundwater store for the 2011–12 year

Description		Volume (ML)
		Northern Basin	Southern Basin	Whole region
	Opening balance (30 June 2011)	440,728	913,498	1,354,226
add	Total 10 Groundwater inflows	1,476,078	4,695,757	6,171,835
minus	Total 18 Groundwater outflows	355,374	1,140,646	1,496,020
minus	Closing balance (30 June 2012)	1,548,941	2,464,674	4,013,615
	Balancing item – groundwater store	12,491	2,003,935	2,016,426

 

Information on balancing item – groundwater store is available under Supporting information of line item 25.1 Unaccounted–for difference.

Changes in the groundwater store volume of the water table aquifers for which data are available during the 2011–12 year were evaluated using aquifer characteristics and groundwater level measurements (see quantification methods given below). Table 9 reports on changes in the groundwater store volume of the watertable aquifers for the sustainable diversion limit (SDL) areas within region for which data were available.

Table 9  Volumetric values of changes in groundwater storage in the MDB region for the 2011–12 year

Groundwater resource plan area	Groundwater SDL area		State	Change in groundwater storage in the 2011–12 year (ML)1	Method used to quantify change in groundwater storage2	Groundwater asset volume (ML)3	Change in groundwater storage relative to groundwater asset (%)
	Code	Name
Gwydir Alluvium	GS24	Lower Gwydir Alluvium	NSW	550,721	The Bureau method	40,954	1345%
Namoi Alluvium	GS29	Lower Namoi Alluvium	NSW	83,370	NSW model	97,654	85%
	GS47	Upper Namoi Alluvium	NSW	68,353	NSW model zone 2–12	141,236	48%
Macquarie–Castlereagh Alluvium	GS26	Lower Macquarie Alluvium	NSW	47,055	NSW model zone 1 to 6	71,981	65%
Sub-total Northern Basin				749,499		–	–
Lachlan Alluvium	GS25	Lower Lachlan Alluvium	NSW	62,100	NSW model	124,743	50%
Murrumbidgee Alluvium	GS28	Lower Murrumbidgee Alluvium, shallow; Shepparton formation	NSW	308,751	NSW model	287,478	107%
	GS31	Mid-Murrumbidgee Alluvium, shallow; Shepparton formation	NSW	14,840	NSW Model	–	–
Murray Alluvium	GS27	Lower Murray Alluvium, shallow; Shepparton formation	NSW	163,477	The Bureau method	205,344	80%
	GS46	Upper Murray Alluvium, Shallow Shepparton formation	NSW	4,387	The Bureau method	14,109	31%
Goulburn–Murray	GS8	Goulburn-Murray: Ovens–Kiewa sedimentary plain	Vic.	33,339	The Bureau method	254,372	102%
	GS8	Goulburn–Murray: Victorian Riverine sedimentary plain, shallow; Shepparton formation	Vic.	226,670	The Bureau method
Wimmera–Mallee (groundwater)	GS09	Wimmera Mallee sedimentary plains	Vic.	-656,891	The Bureau method	18,477	-3,555%
Eastern Mount Lofty Ranges	GS01	Angas Bremer (Quaternary sediments and Murray Group limestone)	SA	5,831	The Bureau method	6,500	90%
South Australian Murray	GS03	Mallee (Murray Group limestone)	SA	50,715	The Bureau method	5,138	987%
	GS05	Peake–Roby–Sherlock (unconfined)	SA	3,417		5,983	57%
Sub-total Southern Basin				216,636		–	–
Total for the region				966,135		–	–

 

¹Change in groundwater storage is the estimated difference between all inflows to the store and outflows from the store for the 2011–12 year (see 'Method' in 'Quantification approaches' for more details). Changes in store volumes (based on aquifer characteristics) shown in the table for selected SDL areas are not reflected in the water accounting statements for the MDB region. Therefore, there is no relation between the changes in storage volumes shown in the table, and included in Table 7 and the water accounting statements.

² See 'Method' in quantification approaches for more details.

³ Groundwater asset volumes shown in the table are long-term estimates of volumes for extraction plus landholder rights (see line item 2.5 Other groundwater assets). The table does not include all the aquifers considered in the water accounting statements. Therefore, the total for the asset volumes shown in the table is less than the total asset volume shown in the water accounting statements and the line item 2.5 Other groundwater assets.

NSW = New South Wales, Vic. = Victoria, SA = South Australia, The Bureau = Bureau of Meteorology

 

Table 9 also indicates what method was used to quantify the change in groundwater storage in each SDL area: either the Bureau method based on measured groundwater levels or the New South Wales groundwater model results (New South Wales models).

With time, trends in the yearly changes in groundwater storages will provide more useful information about the adequacy of the extraction limits set in the groundwater management plans. For instance, a long-term trend of negative changes in groundwater storage may indicate that groundwater in an area may be over allocated. This year most of the changes indicate an increase in groundwater storage which is consistent with the above average rainfall observed during the reporting year and the year before.

Quantification approaches for the estimation of changes in groundwater stored in aquifers

Data source: The Bureau method

Bore locations and groundwater level data in South Australia were sourced from the Drillhole Enquiry System (Department of Environment, Water and Natural Resources 2012).

Bore locations and groundwater level data in Victoria were sourced from the Department of Sustainability and Environment (DSE) and Victorian Department of Primary Industries (DPI) through a database developed by the University of Melbourne.

Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

The geographic information system (GIS) data relating to the boundaries of the aquifers and SDL regions were received from the Murray–Darling Basin Authority.

Data source: NSW Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Data provider

The Bureau and New South Wales Office of Water.

Method: The Bureau method

Change in extractable storage is estimated using a simple geographic information system (GIS) approach based on measured groundwater levels and aquifer properties. Firstly, groundwater levels at the start (1 July 2011) and the end (30 June 2012) of the 2011–12 year were estimated. This was achieved by considering all groundwater level measurements between March 2011 – October 2011 and March 2012 – October 2011, respectively, and using the measurements closest in time to interpolate the start and end levels. The estimated groundwater levels on the start and end dates were then spatially interpolated to grids using kriging with external drift and the 9" Digital Elevation Model as an external driver following the methodology presented in Peterson et al. (2011). The change in volume within the sedimentary area was calculated using these interpolated groundwater level surfaces.

These volumes were multiplied by appropriate specific yield values (Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and 2010b) to convert the volume to a change in groundwater storage. Finally, change in storage was only considered within a 10 km mask of each groundwater observation bore to ensure an appropriate influence from the change in each bore and the volume was reported for the water table aquifer only. Groundwater storage outside these buffer areas was assumed constant throughout the year given that there is no data available.
 

Method: New South Wales Office of Water method

New South Wales groundwater (see list of applicable SDL areas in Table 9) model outputs were used to evaluate the changes in groundwater storage. The change in groundwater storage derived from the groundwater models in New South Wales included all the groundwater model layers (not just the water table aquifer layer).

Uncertainty: The Bureau method

Uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e. g. groundwater levels, specific yield) was not specified and hence the impacts of such uncertainty on the change in storage were not estimated.

The change in storage estimations were calculated from the interpolated groundwater level grids produced using kriging with external drift and the 9" Digital Elevation Model as an external driver. Use of other interpolation methods may impact the values of the groundwater level grids and hence the estimated values for change in groundwater storage.

Uncertainty: New South Wales Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled change in extractable storage from outputs of a MODFLOW groundwater model.

Approximations, assumptions, caveats and limitations

The Bureau method:

• Change in groundwater storage outside the buffer areas is assumed zero given that no data is available for calculation.

• Change in groundwater storage was not calculated for confined aquifers. Under normal circumstance, the annual change in storage is considered to be negligible for confined aquifers due to their very low storage coefficient, which is much lower than the specific yield of water table aquifers (Freeze and Cherry 1979, Johnson 1967). As long as confined aquifers remain saturated, changes in piezometric levels (i. e. aquifer pressure) usually cause small changes in water volumes stored in the aquifers; the changes are equivalent to the volumetric expansion/contraction of the water and the pore space.

• The specific yield values used in each water table aquifer are presented in Table below.

New South Wales groundwater models (see list of applicable SDL areas concerned in Table 9):

• Details on the limitations of groundwater models used by New South Wales Office of Water can be accessed through its webpage on Water accounting.

 

 

Table 10  Specific yield values used in calculating the change in groundwater storage with the Bureau method. The specific yield values was sourced from CSIRO and SKM 2010a and b)

SDL area	Specific Yield
Northern Basin
Lower Gwydir Alluvium	0.200
Southern Basin
Lower Murray Alluvium, shallow; Shepparton formation	0.100
Upper Murray Alluvium, shallow, Shepparton formation	0.100
Goulburn–Murray: Ovens–Kiewa sedimentary plain	0.150
Goulburn–Murray: Victorian Riverine sedimentary plain, shallow; Shepparton formation	0.100
Wimmera–Mallee sedimentary plains	0.115
Angas Bremer (Quaternary sediments and Murray Group limestone)	0.100

Groundwater inflow from other SDL areas within a segment has been calculated for selected SDL areas. Table 11 and Table 12 provide details for the Northern Basin and the Southern Basin.

 

Table 11  Details of groundwater inflow to a SDL area from other SDL areas within the Northern Basin

SDL area	Volume (ML) for the 2011–12 year for the 2012 Account	Volume (ML) for the 2010–11 year for the 2012 Account	Volume (ML) for the 2010–11 year reported in the 2011 Account
Lower Gwydir Alluvium – unconfined	380	122	279
Lower Gwydir Alluvium – confined	1	0
Lower Namoi – unconfined	10	16	667
Lower Namoi – confined	8,480	8,620	Not reported

 

Table 12  Details of groundwater inflow to a SDL area from other SDL areas within the Southern Basin

SDL area	Volume (ML) for the 2011–12 year for the 2012 Account	Volume (ML) for the 2010–11 year for the 2012 Account	Volume (ML) for the 2010–11 year reported in the 2011 Account
Lower Lachlan (unconfined and confined)	370	2,550	370
Lower Murrumbidgee Alluvium (unconfined)	1,030	16	1,030
Lower Murrumbidgee Alluvium (confined)	9,330	9,600	9,330
Mid-Murrumbidgee Alluvium (unconfined)	6,982	3,909	–
Mid-Murrumbidgee Alluvium (confined)	2,671	1,319	–
Lower Murray Alluvium (shallow; Shepparton formation)	41,056	39,674	17,034
Lower Murray Alluvium (deep; Renmark Group and Calivil formation)	871,425	851,486	276,448
Goulburn–Murray (unconfined: Ovens–Kiewa sedimentary plains including Upper Murray)	978	1,041	4
Goulburn–Murray (confined: Ovens–Kiewa including Upper Murray)	423	388	212
Goulburn–Murray: Victorian Riverine sedimentary plain (shallow; Shepparton formation)	30,609	28,980	6,280
Goulburn–Murray: Victorian Riverine sedimentary plain (deep; Calivil and Renmark formations)	44,717	47,732	61,413
Wimmera–Mallee sedimentary area (unconfined)	152,472	156,235	–
Wimmera–Mallee sedimentary area (confined)	168,524	168,070	–
Angas Bremer (Quaternary sediments and Murray Group limestone)	7,239	7,121	–
Angas Bremer (confined)	–	–	–
Mallee (Murray Group limestone) and Peake–Roby–Sherlock (unconfined)	77,784	77,616	–
Mallee (Murray Group limestone) and Peake–Roby–Sherlock (confined)	1,526	1,618	–

Quantification approaches for the estimation of inflow to a SDL area from other SDL areas within a segment – Northern Basin

Two estimation methods, the Bureau method and New South Wales Office of Water method were applied in calculations (see line Item 10.1 Groundwater inflow from outside region for more details on the methods).

Data source

The Bureau method:

• Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

• Bore locations and groundwater level data in Queensland were sourced from Department of Environment and Resource Management.

• The GIS data relating to the boundaries of the SDL regions were provided by the Murray–Darling Basin Authority.

New South Wales Office of Water method:

• The outputs of the New South Wales groundwater models available within selected SDL areas were used.

 Data Provider

The Bureau and New South Wales Office of Water.

 Method: The Bureau method

The regional groundwater flow across selected SDL areas within the Northern Basin was considered. The selected SDL areas represent major groundwater resources for the Northern Basin. Groundwater flow was estimated for the unconfined and selected confined aquifers that underlie these boundaries.

Groundwater flow was calculated using a simple GIS approach based on Darcy's Law. Groundwater levels were interpolated for seasons using kriging with an external drift from 9" Digital Elevation Model following the methodology presented in Peterson et al. (2011) and simple GIS analysis for the watertable and confined aquifers, respectively. The seasonal values were aggregated to the 2011–12 year.

Seasonal groundwater flow-grids were derived from groundwater level grids, aquifer thickness and hydraulic conductivity using a modification of the ArcGIS Darcy Velocity tool. Groundwater flow across selected flow boundaries was then calculated using a simple GIS analysis and seasonal values were aggregated to the 2011–12 year.

Method: New South Wales Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information: The Bureau method

The uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e.g. groundwater levels, hydraulic conductivity) was not specified and unknown and hence the impacts of such uncertainty on the calculated groundwater flow were not estimated.

The regional flow estimations were based on the interpolated groundwater level grids produced using kriging with an external drift from 9" Digital Elevation Model and simple GIS analysis for the water table and confined aquifers, respectively. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow; however, the regional flow estimated with interpolated groundwater levels using GIS analysis was compared with a simple groundwater flow model developed on MODFLOW model (United States Geological Survey 2013). The results from the two methodologies indicated a 6 – 7% difference.

Groundwater flow was estimated for a simplified boundary constructed from a series of line segments. Groundwater flow across this boundary was calculated using the method described above. The uncertainty surrounding this simplification was not analysed.

Uncertainty Information: New South Wales Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats and approximations

The Bureau method:

• Regional flow estimations are provided for the SDL areas indicated in Table 11 only. Due to the fact that not all the hydrological processes within the Northern Basin have been taken into consideration, the total regional inflows to the Northern Basin are not comparable with that provided in Table 11.

• Constant aquifer thicknesses were assumed for the Lower Gwydir SDL region. The thicknesses were consistent with those reported in the RAAM report (Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and 2010b) and Lower Gwydir Valley groundwater model (Huseyin 2002). Aquifer conductivity values were also used from the Lower Gwydir Valley Groundwater Model (Huseyin 2002). Transmissivity values are calculated by multiplying the aquifer thickness with the relevant hydraulic conductivity.

New South Wales Office of Water method:

• Details on the limitations of groundwater models used by New South Wales Office of Water are available in General Purpose Water Accounting Reports – Groundwater methodologies.

Quantification approaches for the estimation of inflow to a SDL area from other SDL areas within a segment – Southern Basin

Two estimation methods, the Bureau method and New South Wales Office of Water method, were applied in calculations (see line Item 10.1 Groundwater inflow from outside region for more details on the methods).

Data source

The Bureau method:

• Bore locations and groundwater level data in South Australia were sourced from the Drillhole Enquiry System (Department of Environment, Water and Natural Resources, 2012).

• Bore locations and groundwater level data in Victoria were sourced from the Department of Sustainability and Environment (DSE) and Victorian Department of Primary Industries (DPI) through a database developed by the University of Melbourne

• Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

New South Wales Office of Water method:

• The New South Wales Office of Water has developed a series of groundwater models for selected areas using the groundwater flow simulation computer program MODFLOW. The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Data Provider

The Bureau and New South Wales Office of Water.

Method: The Bureau method

The regional groundwater flow across selected SDL areas within the Southern Basin was considered. 

Groundwater flow was calculated using a simple GIS approach based on Darcy's Law. Groundwater levels were interpolated for seasons using kriging with an external drift from 9" Digital Elevation Model following the methodology presented in Peterson et al. (2011), and simple GIS analysis for the water table and confined aquifers, respectively. The seasonal values were aggregated to the 2011–12 year.

Seasonal groundwater flow-grids were derived from groundwater level grids, aquifer thickness and hydraulic conductivity using a modification of the ArcGIS Darcy Velocity tool. Groundwater flow across selected flow boundaries was then calculated using a simple GIS analysis and seasonal values were aggregated to the 2011–12 year.

Method: New South Wales Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information: The Bureau method

The uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e.g. groundwater levels, hydraulic conductivity) was not specified and unknown and hence the impacts of such uncertainty on the calculated groundwater flow were not estimated.

The regional flow estimations were based on the interpolated groundwater level grids produced using kriging with an external drift from 9" Digital Elevation Model and simple GIS analysis for the water table and confined aquifers, respectively. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow; however, the regional flow estimated with interpolated groundwater levels using GIS analysis was compared with a simple groundwater flow model developed on MODFLOWmodel (United States Geological Survey 2013). The results from the two methodologies indicated a 6 – 7% difference.

Uncertainty information: New South Wales Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats and approximations

The Bureau method:

• Regional flow estimations were provided for the aquifers indicated in Table 12 only and also due to the fact that not all the hydrological processes within the Southern Basin have been taken into consideration, the total regional inflows to the Southern Basin are not comparable with that provided in Table 12.

• The Geofabric version 2 (Bureau of Meteorology 2011a), and Southern Riverine Plains groundwater model (Goode and Barnett 2008) were used to estimate aquifer thicknesses. The hydraulic conductivity values were sourced from Mallee Prescribed Wells Area – Murrayville Water Supply Protection Area groundwater model (Barnett and Osei-bonsu 2006), Southern Riverine Plains groundwater model (Goode and Barnett 2008) and the report on sustainable extraction limits derived from the recharge risk assessment method – New South Wales (Commonwealth Scientific and Industrial Research Organisation and Sinclair Knight Merz 2010a and 2010b). The transmissivity values were calculated by multiplying the aquifer thickness with the relevant hydraulic conductivity.

•  It is possible that small differences occur between the University of Melbourne database and the DSE groundwater database (from which bore locations and groundwater level data in Victoria were sourced).

Groundwater outflow to other SDL areas within a segment has been calculated for selected SDL areas. Tables 13 and 14 provide details for the Northern Basin and the Southern Basin.

  

Table 13  Details of groundwater outflow from a SDL area to other SDL areas within the Northern Basin

SDL area	Volume (ML) for the 2011–12 year for the 2012 Account	Volume (ML) for the 2010–11 year for the 2012 Account	Volume (ML) for the 2010–11 year reported in the 2011 Account
Lower Gwydir Alluvium (unconfined)	4,998	5,269	1,109
Lower Gwydir Alluvium (confined)	623	619	–
Lower Namoi (unconfined)	997	1,020	260
Lower Namoi (confined)	5,416	5,470	–

 

Table 14  Details of groundwater outflow from a SDL area to other SDL areas within the Southern Basin

SDL area	Volume (ML) for the 2011–12 year for the 2012 Account	Volume (ML) for the 2010–11 year for the 2012 Account	Volume (ML) for the 2010–11 year reported in the 2011 Account
Lower Lachlan (unconfined and confined)	24,750	26,850	24,750
Lower Murrumbidgee Alluvium (unconfined)	4,260	973	4,260
Lower Murrumbidgee Alluvium (confined)	118,190	5,080	118,190
Mid-Murrumbidgee Alluvium (unconfined)	1,109	137	–
Mid-Murrumbidgee Alluvium (confined)	2,157	2,380	–
Lower Murray Alluvium (shallow; Shepparton formation)	43,484	43,484	8,720
Lower Murray Alluvium (deep; Renmark Group and Calivil formation)	567,854	567,854	184,377
Goulburn–Murray (unconfined: Ovens–Kiewa sedimentary plains including Upper Murray)	12,159	11,286	1,729
Goulburn–Murray (confined: Ovens–Kiewa including Upper Murray)	13,209	12,891	7,751
Goulburn–Murray: Victorian Riverine sedimentary plain (shallow; Shepparton Formation)	28,722	29,270	10,133
Goulburn–Murray: Victorian Riverine sedimentary plain (deep; Calivil and Renmark formations)	157,100	152,157	117,410
Wimmera– Mallee sedimentary area (unconfined)	146,369	147,977	–
Wimmera– Mallee sedimentary area (confined)	516,309	514,454	–
Angas Bremer (Quaternary sediments and Murray Group limestone)	2,210	1,958	–
Angas Bremer (confined)	–	–	–
Mallee (Murray Group limestone) and Peake–Roby– Sherlock (unconfined)	73,181	72,299	–
Mallee (Murray Group limestone) and Peake–Roby– Sherlock (confined)	1,538	1,501	–

 

Quantification approaches for the estimation of outflow from a SDL area to other SDL areas within a segment

Two estimation methods, the Bureau method and New South Wales Office of Water method, were applied in calculations (see line Item 10.1 Groundwater inflow from outside region for more details on the methods).

Data source

The Bureau method:

• Bore locations and groundwater level data in New South Wales were sourced from New South Wales Office of Water.

New South Wales Office of Water method:

•  The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Data provider

The Bureau and New South Wales Office of Water.

Method: The Bureau method

The regional groundwater flow across selected SDL areas within a segment was considered. The selected SDL areas represent major groundwater resources for the segment.

Groundwater flow was calculated using a simple GIS approach based on Darcy's Law.

Method: New South Wales Office of Water method

The outputs of the New South Wales groundwater models available within selected SDL areas were used.

Uncertainty information: The Bureau method

The uncertainty estimate was not quantified.

The uncertainty in the field-measured data (e.g. groundwater levels, hydraulic conductivity) was not specified and unknown and hence the impacts of such uncertainty on the calculated groundwater flow were not estimated.

The regional flow estimations were based on the interpolated groundwater level grids. Use of different interpolation methods may impact on the values of the groundwater level grids and hence the estimated regional flow;  however, a comparison of the methodology was carried out using a simple groundwater flow model developed on MODFLOW model (United States Geological Survey 2013). The results from the two methodologies indicated a 6 – 7% difference.

Groundwater flow was estimated for a simplified boundary constructed from a series of line segments. Groundwater flow across this boundary was calculated using the method described above. The uncertainty surrounding this simplification was not analysed.

Uncertainty information: New South Wales Office of Water method

The uncertainty estimate was not quantified.

It is currently not feasible to estimate the uncertainty of modelled regional flow from outputs of a MODFLOW groundwater model.

Assumptions, limitations, caveats and approximations

The Bureau of Meteorology method:

• Regional flow estimations were provided for the SDL areas shown in tables 14 and 15 only. Due to the fact that not all the hydrological processes within the segments have been taken into consideration, the total regional outflow are not comparable with that provided in tables 14 and 15.

New South Wales Office of Water method:

Details on the limitations of groundwater models used by the New South Wales Office of Water are available in General Purpose Water Accounting Reports - Groundwater methodologies.

The purpose of this note is to provide a consolidated report on the off-channel water storages within the Murray–Darling Basin (MDB) region during the 2011–12 year. Information on storage volumes, inflows and outflows for the off-channel water storages is provided in this note.

The off-channel water storages consists of all private reservoirs that are used to harvest runoff before reaching the surface water store or that are filled by pumping from a watercourse or groundwater.

The store includes constructed storages that are not connected either seasonally or perennially to rivers, filled predominantly by local catchment runoff. They include off-channel farm dams, run-off dams, hill-side dams, industrial, commercial and mining water storages. They exclude on-channel farm dams and other storages.

The off-channel water storages for the 2012 Account were determined from waterbody mapping conducted by Geoscience Australia as those that are:

• not named storages (assuming that any storage with a name is unlikely to be a off-channel storage)

• above 600 m in elevation or are in areas that receive greater than 400 mm per annum in precipitation and are not within 50 m of a major or perennial stream.

The above rules attempt to divide storages into those that are likely to be filled primarily by local catchment runoff and those which are filled by abstraction from surface water, groundwater or floodplain harvesting.

As discussed in General description in 'Physical information' in the 'Contextual information', the off-channel water store has been excluded from the scope of the MDB region for the purposes of the 2012 Account, because it is constituted of water already abstracted from the shared pool of water resources. Therefore off-channel water store reporting line items do not appear in the water accounting statements. Off-channel water storages influence water assets and water liabilities recognised in the water accounting statements though, as they harvest water from the landscape and thus reduce groundwater recharge and runoff into surface water.

Table 15 shows that the total off-channel water store increased during the 2011–12 year in the MDB region.

 

Table 15  Off-channel water storage volume at the start and end of the 2011–12 year for the MDB region

Description	30 June 2012 (ML)			30 June 2011 (ML)
	Northern Basin	Southern Basin	Whole region	Northern Basin	Southern Basin	Whole region
27.1 Off-channel water storages	534,236	618,502	1,152,737	513,351	618,587	1,131,938
27.2 Rainwater tanks	–	–	–	–	–	–
Total	534,236	618,502	1,152,737	513,351	618,587	1,131,938

 –  = Data not available

 

The water volume held in off-channel water storages within the MDB region at the end of the 2011–12 year was more than that at the start (1 July 2011). This was primarily attributed to the high rainfalls and inflows recorded in the Northern Basin of the region during the 2011–12 year. Some areas in the Northern Basin recorded their highest annual rainfall on record (see Rainfall in 'Climate overview' in the 'Contextual information').

The inflow and outflow volumes for the off-channel water store during the 2011–12 year are given in Table 16.

 

Table 16  Volume of inflows and outflows for the off-channel water store during the 2011–12 year

Description	Volume (ML)
	Northern Basin	Southern Basin	Whole region
Off-channel water inflows
30.1 Precipitation on off-channel water store	849,216	435,568	1,284,785
30.2 Groundwater discharge into off-channel water store	–	–	­–
30.3 Runoff harvesting into off-channel water store	742,969	577,978	1,320,947
30.4 Surface water diversion into off-channel water store	–	–	­–
30.5 Groundwater extraction into off-channel water store	–	–	­–
Total Off-channel water inflows	1,592,185	1,013,546	2,605,732
Off-channel water outflows
31.1 Evaporation from off-channel water storages	1,039,856	571,476	1,611,332
31.2 Leakages from off-channel water storages	–	–	­–
31.3 Off-channel water abstraction	531,432	442,169	973,602
Total Off-channel water outflows	1,571,288	1,013,645	2,584,934
Balancing item – off-channel water	12	(14)	(1)
Change in off-channel water storage	20,885	(85)	20,799
Opening off-channel water storage	513,351	618,587	1,131,938
Closing off-channel water storage	534,236	618,502	1,152,737

– = data not available

 

Precipitation on to off-channel water store and runoff harvesting into them decreased by 10% and 13% respectively for the 2011–12 year compared to the 2010–11 year. Most likely due to that reason, water use from off-channel storages decreased by 12% in the 2011–12 year compared to the previous years' use.

This volume represents the volume necessary to reconcile the opening and closing balances of the off-channel water storage with the physical water inflows and outflows. The difference was calculated according to Table 17.

 

Table 17  Balancing item – off-channel water 2011–12 year

Description	Account	Volume (ML)
	Opening balance (30 June 2011)	1,131,938
add	Total 30 Off-channel water inflows	2,605,732
minus	Total 31 Off-channel water outflows	2,584,934
minus	Closing balance (30 June 2012)	1,152,737
	Balancing item – off-channel water store	(1)

 

The calculation of the water balance on the off-channel water store yielded a balance of -1 ML. This is negligible compared to the opening and closing balances. Despite this, one should note that the values presented for off-channel storages remain broad estimates based on numerous assumptions and simplifications (see quantification approaches of the various line items linked from the tables).