National Water Account 2015

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Region overview

Contextual information

Physical information

Administration

Water rights

Climate and water overview

Water Accounting Statements

Water Assets and Water Liabilities

Changes in Water Assets and Water Liabilities

Water Flows

Notes

Accounting policies

Supporting information

Quantification approach

Reconciliations

Water resources & systems

Water access & use

Future outlook

References

Accountability statement

Murray–Darling Basin: Supporting information

Introduction

The following set of notes provides consolidated reports for each of the water stores and systems within the  Murray–Darling Basin region during the 2014–15 year. The water stores and systems included in the region are shown in Figure N1.

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

Figure N1 Water stores and systems within the Murray–Darling Basin region

Information on all water flows to and from each water store 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 N2.

Figure N2 Between-store flows that occur within the Murray–Darling Basin region

The between-store flows and transfers (Figure N2), which are eliminated from the region's water accounting statements, are shown in italics throughout the following set of notes.

Surface water store

The Murray–Darling Basin region surface water store has three components:

• storages
• rivers
• lakes and wetlands.

A reconciliation of the surface water Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N2. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

Physical surface water asset volumes in the Murray–Darling Basin region at 30 June 2015 were:

• storages—9,681,284 ML
• rivers—897,210 ML
• lakes and wetlands—1,865,132 ML
• other surface water assets—15,103 ML.

The overall storage volume within the Murray–Darling Basin decreased during the 2014–15 year from 57% to 42% capacity. The location of each storage within the Murray–Darling Basin region and the volume of water in each storage (including dead storage) as a percentage of total storage capacity on June 30 2015 is shown in Figure N3. It should be noted that there is a difference between total storage volume reported here with that recorded on the MDBA website. This is because the Murray–Darling Basin Authority reports on storages that are Government-owned, used primarily for irrigation supply and have capacity of more than 10,000 ML.

Below average rainfall during the 2014–15 year (see Climate and water overview) meant the storage volume decreased during the year for almost all of the storages throughout the region. Storage volumes in the larger reservoirs (>400,000 ML capacity) generally dropped by 20–50% during the year as shown in Figure N4.

Figure N3 Percentage-full volume on 30 June 2015 for major storages within the Murray–Darling Basin region

Figure N4 Total volume of water in storages with capacity greater than 400,000 ML in Murray–Darling Basin region at 30 June 2015 compared with the previous year and the 5-year average

The volume of water in rivers decreased by 20% during the 2014–15 year from 1,126,812 ML at 30 June 2014 to 897,210 ML at 30 June 2015. The total river volume includes water held in the main river channels (494,020 ML) as well as water held in weirs and other ponds and storages along the river (403,190 ML).

The volume of water in lakes and wetlands within the Murray–Darling Basin region (1,865,132 ML) changed only marginally during the 2014–15 year. Not all of the region's lakes and wetlands are reported as some storage volumes could not be quantified due to a lack of available data. Of the lakes and wetlands included in the account, almost 90% of the total water is held in Lake Alexandrina.

'Other surface water assets' (15,103 ML) refers to the Rocky Valley Reservoir located in the Kiewa sustainable diversion limit (SDL) area in Victoria. Rocky Valley Reservoir does not form part of the entitlement system within the Murray–Darling Basin region. It is a storage owned by a hydro-electric operator and the volume released each year is subject to operator's water licence. No orders can be placed on the storage for delivery of water to the entitlement system. It does not reflect a volume that can be used to support the total volume in storages. It is potentially an asset, although there is some doubt about when the asset can be claimed because it is not available to settle claims for water until the hydro-operator physically makes the release.

Non-physical assets

'Non-physical surface water assets' includes an inter-region claim at 30 June 2015.

Inter-region claim

The volume at 30 June 2015 was 1,238,860 ML. It refers to a claim on the Snowy Hydro Limited (Snowy Hydro) for the balance of the required annual release (RAR) to the Tumut and Murray rivers. The RAR is set at the commencement of the Snowy Hydro water year (1 May–30 April) for delivery over the ensuing 12 months.

In drier than average times, a dry Inflow sequence volume (DISV) allowance is made for reduced inflows to the Snowy Mountains Scheme. Under the original Snowy water licence, the DISV reduced the RAR when inflows were lower than the historical drought sequence volumes and increased the RAR as inflows recovered; however, in the Snowy water licence amendments that took effect on 4 October 2011, the RAR formula (refer to the downloadable table) was modified to deduct (non-negative) the DISV increase rather than add DISV from the previous 1 March and subtract the current DISV. This change results in the same reduced RAR during continuing dry conditions, but when inflows improve (when recovering from a DISV state) the DISV recover volumes are instead  stored in drought accounts rather than increasing the RAR.  The DISV increase adjustments are made to the RAR on a monthly basis through the Snowy water year up to 1 March.

Environmental water savings transferred from the Murrumbidgee River and the Murray River to the Snowy River or the montane streams result from entitlements acquired in the Murray–Darling Basin region through completion of water-saving infrastructure projects or purchases of entitlements. When allocations are announced against these entitlements, the RAR (claim against Snowy Hydro) is reduced. Snowy Hydro subsequently makes these environmental releases to the Snowy River and other montane streams.

Water available to the Murray–Darling Basin region under inter-region claims (1,921,622 ML), is in addition to the balance of RAR at the beginning of the year; which includes:

• Estimated volume of RAR for the year: Estimated RAR for the 2014-15 year (1,198,860 ML) includes the dry inflow sequence volume (DISV) adjustments made to the RAR during the year on a month-by-month basis and other RAR adjustments.
• The volume of water transferred from Glenelg catchment to the region during the year (2,762 ML): Grampians Wimmera–Mallee Water transferred water from the Glenelg catchment to the region during the 2014–15 year. This transfer has been made as specified in a Victorian bulk entitlement. The transfer is made from the Glenelg River upstream of and including Rocklands Reservoir, and the first and second Wannon creeks upstream of and including the weirs to the Wimmera–Mallee supply system, located within the Murray–Darling Basin region.

Before deciding the RAR on 30 June 2015, a 100,000 ML of decrease to the carryover volume was agreed between parties to the Snowy Water Licence.

Liabilities

Surface water liabilities in the Murray–Darling Basin region refer to the volume of surface water allocation remaining on licensed entitlements at the end of the 2014–15 year for:

• individual users—1,805,817 ML 
• environmental purposes—665,419 ML
• urban water system—0 ML.

Water supply licences for individual users and environmental purposes have carryover provisions. A portion of the unused component of the annual allocation can be carried over to the following year. This is equal to the allocation remaining at the end of the 2014–15 year (Table N3 and Table N4). There is no carryover provisions for urban water entitlements, so the portion of surface water allocation that has not been taken by the end of the year is forfeited (Table N5). Details are provided in tables N3–N5.

A more detailed description of all surface water entitlements and allocation arrangements in the Murray–Darling Basin region is provided in the Surface water rights note.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the surface water store in the Murray–Darling Basin region is provided in Figure N5

Figure N5 Water inflows and outflows for the surface water store within the Murray–Darling Basin region during the 2014–15 year

Surface water inflows

Total inflows to surface water store were 17,814,473 ML and comprised the following:

• Precipitation—1,199,912 ML
• Delivery: inter-region inflow—0 ML
• Discharge: groundwater—311,800 ML
• Runoff—14,403,148 ML
• Point return: irrigation—297,113 ML
• Delivery: inter-region agreement—1,253,588 ML
• Return flow: environmental purposes—314,011 ML
• Discharge: wastewater system—34,901 ML.

The largest surface water inflow was 'Runoff to surface water' (14,403,148 ML). This volume is about 30% less than the previous year, which reflects the relatively poor rainfall conditions experienced across the Murray–Darling Basin region (See Rainfall section in 'Climate and water overview'). Similarly, precipitation that fell on the major storages and rivers within the region (1,199,912 ML) decreased compared with the previous year.

The remaining natural surface water inflow is groundwater discharge. This represents the volume of water that discharged from aquifers to rivers (311,800 ML). This volume increased marginally compared with the previous year.

The surface water transfer is a delivery by inter-region agreement (1,253,588 ML), which refers to water delivered from the Snowy Hydro (1,250,826 ML) and from Glenelg River (2,762 ML). The discretionary flow made by Snowy Hydro to the Murray and Tumut rivers was 0 ML during the 2014-15 year.

'Point return: irrigation' (297,113 ML) refers to the volume of return flow from the Coleambally irrigation area to the Murrumbidgee river system (12,210 ML) and from the Broken Creek and Torrumbarry irrigation areas to the Victorian Murray river system (284,903 ML).

'Return flow: environmental purposes' (314,011 ML) refers to the held environmental water volume returning back to rivers. The SDLs in Victoria which reported return flows were: Goulburn—250,727 ML; Campaspe—18,214 ML; and Victorian Murray—45,069 ML.

'Discharge: wastewater system' (34,901 ML) refers to treated water discharged from the wastewater system to rivers from treatment plants in the Murrumbidgee, ACT, Goulburn and Victorian Murray SDL units.

Surface water outflows

Total outflow from surface water store was 21,543,148 ML during the 2014–15 year and comprised the following:

• Evaporation—4,871,102 ML
• Outflow—1,196,000 ML 
• Recharge: groundwater—140,620 ML
• Overflow: landscape—21,490 ML 
• River and floodplain losses—5,815,382 ML
• Diversion: statutory rights—27,692 ML
• Non-allocated diversion: individual users—778,334 ML
• Non-allocated diversion: environmental purposes—120,550 ML
• Non-allocated diversion: urban system—6,154 ML
• Allocated diversion: individual users—6,561,372 ML
• Allocated diversion: environmental purposes—1,638,632 ML
• Allocated diversion: urban system—365,820 ML.

'Evaporation' (4,871,802 ML) from major storages and rivers during the 2014–15 year was higher than the previous reporting year, which may be attributed to the decreased rainfall (and hence cloud cover) that occurred during the year (see Climate and water overview).

'River outflow from the region' (1,196,000 ML) refers to the annual volume of flow from the Murray River to the Southern Ocean during the 2014–15 year. This outflow is 67% of which occurred during the previous year, which primarily reflects the below average flow conditions in the Murray River compared with the flows experienced during the 2013–14 year (see Climate and water overview).

'Groundwater recharge' (140,620 ML), which represents the volume of water that recharged into the aquifers from rivers, decreased compared with the previous year.

'Overflow to the landscape' (21,490 ML) refers to overbank flood spilling of floodwaters that overflow from the river channels onto the floodplain. This volume decreased compared with the previous year, which also may be attributed to the decreased rainfall across the northern section of the region.

'River and floodplain losses' (5,815,382 ML) which includes evaporation, leakage and gauging errors in river inflow and outflow measurements, was calculated by applying a water balance approach. Therefore, any balancing volume for the whole Murray–Darling Basin region is included under this item.

'Diversions under statutory rights' (27,692 ML) is associated with landowner basic rights, riparian rights, stock and domestic rights. Non-allocated diversion volumes are from unregulated streams and unregulated reaches of regulated streams.

Allocated diversion

'Allocated diversion' refers primarily to individual users. During the 2014–15 year, 6,561,372 ML of allocated surface water was diverted to individual users. Since diversions are more than allocations in some water resource plan areas, the diversion volume is presented as a percentage of water availability. Water availability volume in the Murray–Darling Basin region for each water resource plan area is calculated as carryover from the previous year plus the allocation announcement during the year plus the net allocation trade during the year and are available in the downloadable table. Figure N6 shows the surface water diversion to individual users for each water resource plan area against the water availability.

Figure N6 Surface water diversion to individual users by water resource plan area against water availability during the 2014–15 year; volume and percentage of water diverted is also shown

'Allocated diversion for environmental purposes' during the 2014–15 year was 1,638,632 ML, which was 100% of allocation.

'Allocated diversion to the urban water system' during the 2014–15 year was 365,820 ML, which was 72% of the total allocation. Figure N7 shows the total surface water diversion to the urban water system for each water resource plan area.

Figure N7 Surface water diversion to the urban water system by water resource plan area during the 2014–15 year; volume and percentage of allocation diverted is also shown

Further information on diversion against availability (net carryover, allocation announcements and net allocation trade) for the 2014–15 year is provided in the Water access and use note.

Surface water balancing item

The calculation of the surface water balance (Table N6) on the surface water store yielded a balancing item of 0 ML. Uncertainties associated with the measurements and estimations of item volumes result in a balancing volume; however, the balancing volume of 0 ML (Table N6) does not imply that there were no uncertainties associated with the surface water store.

For the Murray–Darling Basin region, the volume of uncertainties is incorporated within the river and floodplain losses and is estimated using a water balance approach. Work is currently underway to more reliably estimate the river and floodplain losses in the region. A more reliable estimate of the river and floodplain losses will allow uncertainties to be quantified separately in the surface water balancing item.

Groundwater store

The Murray–Darling Basin region groundwater store represents the aquifers within the region.

A reconciliation of the groundwater Statement of Water Assets and Water Liabilities and Statement of Water Flows is provided in Table N7. Further details on assets, liabilities, and flows are provided in the following sections.

Methods used to derive reported volumes can be found in the Quantification approach note.

Assets and liabilities

Physical assets

The physical groundwater asset volume in the Murray–Darling Basin region basin at 30 June 2015 was 3,333,740 ML. This volume is based on sustainable diversion limits (SDL) provided by the Murray–Darling Basin Authority. This volume also includes long-term estimates of volumes for extraction, basic landholder rights or unlicensed stock and domestic rights (where these are not included in the long term extraction estimates in the water resource plan), and for New South Wales the volume of supplementary access licence that was available for use in the 2014–15 year.

Non-physical assets

There are no non-physical groundwater assets in the region.

Liabilities

Groundwater liabilities in the Murray–Darling Basin region refer to the volume of groundwater allocation remaining on licence entitlements at the end of the 2014–15 year for:

• individual users—498 ML
• environmental purposes—1,310 ML
• urban water system—0 ML.

Water supply licences for individual users and environmental purposes have carryover provisions. A portion of the unused component of the annual allocation can be carried over to the following year. This is equal to the allocation remaining at the end of the 2014–15 year (Table N8 and Table N9). There is no carryover provision for urban water entitlements, so the portion of groundwater allocation that has not been taken by the end of the year is forfeited (Table N10). Details are provided in tables N8–N10.

A more detailed description of all groundwater entitlements and allocation arrangements in the Murray–Darling Basin region is provided in the Groundwater rights note.

Inflows and outflows

A schematic diagram representing all the inflows and outflows associated with the groundwater store in the Murray–Darling Basin region is provided in Figure N8.

Figure N8 Water inflows and outflows for the groundwater store within the Murray–Darling Basin region during the 2014–15 year

Groundwater inflows

Total inflows to the groundwater store were 2,404,548 ML and comprised the following:

• Inter-region inflow—2,657 ML 
• Inter-region coastal inflow—90 ML 
• Recharge: landscape—2,189,814 ML
• Recharge: surface water—140,620 ML
• Managed aquifer recharge: individual users—267 ML
• Other groundwater increases—71,100 ML.

The largest groundwater inflow was 'Recharge from landscape' (2,189,814 ML), which accounts for more than 95% of the groundwater inflows. The volume of recharge during the 2014–15 year was approximately 39% less than the previous year, reflecting the decrease in rainfall observed across the region during the year (see Climate and water overview). Total volume of rainfall over the entire landscape of the Murray–Darling Basin region was 434,907,200 ML during the 2014–15 year (derived by multiplying the area-averaged rainfall of 412 mm by the area of the region [1,055,600 km²]), which means that 0.5% of the total annual rainfall over the Murray–Darling Basin region contributed to groundwater recharge.

'Inter-region inflow from outside the region' (2,657 ML) refers to the lateral inflow from the Murray Limestone and Renmark Group aquifers near the Murray mouth. Groundwater inflows from the Great Artesian Basin was not measured and cannot be quantified accurately.

'Inter-region coastal inflow' (90 ML), indicates that some minor inflows into the aquifers occurred near the Murray mouth.

'Recharge from surface water' (140,620 ML), represents the volume of water that was recharged into aquifers from rivers; it decreased compared with the previous year.

'Managed aquifer recharge from individual users' (267 ML) represents aquifer recharge from the Angas-Bremer irrigation area in South Australia. During the off-peak irrigation season, water is artificially recharged into the aquifer as storage to meet water demands during the peak of the irrigation season.

'Other groundwater increases' (71,100 ML) reflect changes in long-term extraction estimates and basic landowner rights with the region.

Groundwater outflows

Total outflows from the groundwater store was 3,971,130 ML and comprised the following:

• Inter-region outflow—24 ML
• Inter-region coastal outflow—1,532 ML
• Discharge: landscape—2,106,680 ML
• Discharge: surface water—311,800 ML
• Extraction: statutory rights—221,332 ML
• Non-allocated extraction: other—3,385 ML
• Allocated extraction: individual users—1,274,039 ML
• Allocated extraction: environmental purposes and salt inteception schemes—15,555 ML
• Allocated extraction: urban system—36,783 ML
• Other groundwater decreases—0 ML.

The largest water outflow (2,106,680 ML) from the Murray–Darling Basin region aquifers was 'Discharge to landscape' and was approximately 33% more than the previous year. This decrease reflects the decrease in rainfall experienced across the region during the year (see Climate and water overview). 

'Inter-region outflow' (24 ML) refers to the lateral outflow from the aquifers into the Murray Limestone and Renmark Group aquifers near the Murray mouth. Groundwater outflows to the Great Artesian Basin are not measured and cannot be quantified accurately. 'Inter-region coastal outflow' (1,532 ML) refers to the volume of outflow from the aquifers to the Southern Ocean near the River Murray mouth.

'Discharge to surface water' (311,800 ML), which represents the volume of water that discharged into rivers from aquifers, increased compared with the previous year.

'Extraction under statutory rights' (221,332 ML) is associated with landowner basic rights, riparian rights, and stock and domestic rights. 'Non-allocated extraction: other' (3,385 ML) is associated with other purposes including interception and are reported only from South Australia.

Allocated extraction

Most of the 'allocated extraction of groundwater' is by individual users. During the 2014–15 year, 1,274,039 ML was extracted which was 60% of allocation.

'Allocated extraction for environmental purposes and salt interception schemes' during the 2014–15 year was 15,555 ML, which was 36% of allocation.

'Allocated extraction for urban water system' during the 2014–15 year was 36,783 ML, which was 52% of allocation.

Figures N9 and N10 show the total groundwater extraction to individual users and for urban system respectively, by groundwater resource plan area.

Figure N9 Groundwater extractions to individual users by water resource plan area during the 2014–15 year; percentage of allocation extracted is also shown

Figure N10 Groundwater extractions for urban system by water resource plan area during the 2014–15 year; percentage of allocation extracted is also shown

Groundwater balancing item

The groundwater balance (Table N11) yielded a balance of -1,637,682 ML during the 2014–15 year.

The balancing item volume during the 2014–15 year is due to several reasons. Two explanations for this volume can be provided by:

• changes in groundwater stored in aquifers
• recharge from landscape.

Changes in the groundwater store volume of the water table aquifers for which data was available (-1,330,590 ML) was calculated using aquifer characteristics and groundwater level measurements. The downloadable table records on changes in the groundwater store volume of the watertable aquifers for the SDL resource units for which data was available. The 2014–15 year indicates a decrease in groundwater storage aquifers that is consistent with the below average rainfall conditions observed throughout the region during the 2014–15 year (see Climate and water overview). Over a period of time, trends in the yearly changes in groundwater storages would 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 a SDL resource unit may be over allocated. 

'Recharge from landscape' was approximately 1,337,213 ML less than that reported during the previous year resulting in a decreased contribution (recharge) to total groundwater inflows than in the 2013–14 year; This decrease in recharge reflects the decreased rainfall conditions observed throughout the region during the 2014–15 year (see Climate and water overview).

Unaccounted-for difference

The region's total volume for 'unaccounted-for difference'  for the 2014–15 year was –1,637,682 ML (as recorded in the water accounting statements).

The unaccounted–for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements. It is calculated according to Table N12.

The unaccounted–for difference can also be calculated by tallying the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table N13.

Table N13 shows that the unaccounted-for difference volume is entirely explained by the groundwater store balancing item volume. Surface water store balancing item is considered as 0 because all unaccounted surface water volumes have been included in the item river and flood plain losses. This is further explained under surface water balancing item.