Murray–Darling Basin
Water overview

Significant water events

Rainfall across large areas in the Murray–Darling Basin (MDB) region was generally average to below average for the 2013–14 year. This was the second consecutive year of below average rainfall in the MDB Northern Basin overall, which resulted in some areas in the States of Queensland and New South Wales (NSW) declared to be under drought.

Rainfall in 2013–14 was below average in much of the Northern Basin, contrasting with generally average to below average in the Southern Basin, Figure C1.

The first half of the water year (July 2013–December 2013) was characterised by dry conditions throughout large parts of the MDB, with markedly reduced rainfall in late winter and spring. In the Northern Basin, below average rainfall continued throughout January 2014, resulting in a failed summer wet season with particularly low inflows in the headwater catchments of the Darling River. In the Southern Basin, wetter conditions returned in the second half of the year with many areas experiencing above average rainfall from January to June 2014. South Australia and the areas near the lower Murray River received particularly high rainfall over this period, with a number of significant rainfall events. One event in mid-April 2014 delivered falls of up to 100 mm of rain along the entire length of the River Murray. This was followed by a significant drop in irrigation demand, which remained low until the end of the irrigation season in mid-May 2014 (Murray–Darling Basin Authority 2015a).

Snowy Hydro Limited made above target releases, 0 ML to the Murray River and 151,000 ML to the Tumut River (Murrumbidgee catchment), as discretionary flows during the 2013–14 year (Snowy Hydro Limited 2014).

Information for Queensland

Much of Queensland continued to experience below average rainfall over the past two years (2012–13 and 2013–14), resulting in large areas of the State declared to be under drought conditions during this period. (MDBA 2015a).

Information for New South Wales

Total inflows to Menindee Lakes system between July 2013 and June 2014 were extremely low, totalling only 40,000 ML with Annual Exceedance Probability (AEP) 99% . This is well below the long term median annual inflow of about 950,000 ML. These low inflows were due to poor rainfall throughout the Northern Basin, in particular over the summer period, which led to only low inflows into the Darling River.

Storage levels at the Menindee Lakes  at 1 July 2013 were 1,253,000 ML (72% capacity). Inflows into Menindee Lakes were effectively zero from December 2013 through to March 2014. Higher temperatures over this period also resulted in very high evaporation rates across the storages. In mid-February 2014 the combined storage of Menindee Lakes dropped below 480,000 ML, at which point MDBA no longer had access to call on water releases. As of 30 June 2014, Menindee Lakes system total storage was about 380,000 ML (22% of capacity) (MDBA 2015a).

Flows along the Murrumbidgee River were very low in 2013–14, with inflow to the Murray measured at Balranald totalling about 350,000 ML (AEP 90%). This is well below the long term average of 1,260,000 ML and the median inflow of 880,000 ML. The flow peaked during early August 2013 at 4,100 ML/day.

Downstream of the confluence of the Murray and Darling rivers the flow at Wentworth was primarily driven by Murray flows throughout 2013–14. The flow reached a peak in late September 2013 of 26,000 ML/day (minor flood level occurs at about 87,000 ML/day). The flow decreased to below 10,000 ML/day in early January and remained below this to the end of June 2014 (MDBA 2015a).

Information for Victoria

On 1 July 2013, the volume of water stored at Dartmouth Reservoir was 3,650,141 ML (94% of capacity).  Storage at Dartmouth Reservoir gradually increased from July through to mid-September 2013, when the reservoir reached 99% capacity. The storage then remained above 99% capacity until mid-November. From mid-August to early November 2013, releases were made to prevent flow over the spillway to avoid erosion issues. From late April through to 30 June 2014, releases remained at around minimum flow rates and storage levels began gradually rising. As of 30 June 2014 the storage volume at Dartmouth was 3,513,739 ML (91% capacity).

On 1 July 2013, the volume of water stored at Hume Reservoir it was 1,888,073 ML (63% of capacity). At Hume Reservoir, the 2013–14 year began with releases at a minimum rate of 600 ML/day. High inflows during July and August 2013 resulted in the Hume filling close to 99% and then spilling from mid-August until late September 2013. These spills were not sufficient to generate downstream flows above minor flood levels. Releases to meet environmental, irrigation and normal system demands from October 2013–April 2014 resulted in Hume Reservoir being drawn down to 36% capacity by early April 2014. Reduced demands from mid-April 2014 onwards combined with reasonable inflows caused the storage to begin gradually filling. As of 30 June 2014, the Hume's storage volume had risen to 1,582,875 ML (52% of capacity).

The Barmah Choke was not a major constraint on the delivery of water in 2013–14, even though there was limited water available in Menindee Lakes. This is partly because of the flexible approach used for delivering environmental water. The rule preventing trade of allocations from above to below the 'choke' has been relaxed since September 2007 (MDBA 2015a).

Information for South Australia

South Australia began the 2013–14 year with its full entitlement of 1,850,000 ML for the third consecutive year. No additional dilution flow was delivered to South Australia in 2013–14 as the required monthly trigger volume at Menindee Lakes was not met at any point throughout the water year.

Flow across the border in the first weeks of July 2013 was at entitlement rates. Following increased rainfall and inflows in mid-July 2013,  The MDBA announced 'unregulated flows' within the River Murray system on 17 July 2013. Periods of unregulated flow are declared by the MDBA when it is forecast that flows in the River Murray system cannot be captured in Lake Victoria—because of operating rules, inlet capacity constraints, or storage capacity constraints—and the flow passing through to South Australia will be in excess of its entitlement flow.

Further rain events and responsive catchments during July and August 2013 increased River Murray system inflows, resulting in unregulated flows being extended until 28 October 2013. Although unregulated conditions lasted for over 3 months, the volume of additional flow passing to South Australia was not as large as in recent years, for example the peak flow across the border during this period was around 25,000 ML/day in late September 2013, compared with a peak flow at the same time in 2012–13 of 50,000 ML/day. Unregulated flows ceased on 29 October 2013 and the River Murray system remained fully regulated since then. Between October 2013 and June 2014, South Australia's entitlement flow was further boosted by the delivery of environmental water that had been traded from upstream.

The total annual flow across the South Australian border, including unregulated flow, environmental water, and traded water was about 3,570,000 ML (AEP 67%), compared with 7,020,000 ML total annual flow in the previous year (July 2012–June 2013) and the long term median annual flow of 5,180,000 ML (MDBA 2015a).

Soil moisture

Figure W1 shows that soil moisture was below to very much below average in the Northern MDB region, whereas it was average to above average across the Southern MDB region during the 2013–14 year (compared against the 1970–2014 period). The soil moisture is based on a simple conceptual representation of soil water storage and transfer processes averaged over a 5 km x 5 km grid cell derived from the Australian Water Resources Assessment system landscape model (AWRA-L) version 3.0. The model produces a soil moisture grid for the region at a daily time step, which is then averaged over the entire year to produce an annual soil moisture grid. The annual grid represents the mean daily soil moisture across the region during the year.

Figure W1 Annual soil moisture deciles for the MDB region during the 2013–14 year

Soil moisture distribution shown in Figure W1 aligns with average to below average rainfall conditions experienced across the MDB during the 2013–14 year (see Rainfall in Climate overview). Below average rainfall and generally dry conditions in the soil for Northern Basin catchments, translated into well below average streamflow.

Streamflow

Streamflows were below mean annual flow for the Murray River at Doctors Point, well below mean annual flow for the Darling River at Bourke, and above mean annual flow for Ovens River at Peechelba (figures W4–W6) for the 2013–14 year.

Figures W3–W5 show streamflow patterns, volumes and variations for the three gauging stations selected for streamflow analysis for the 2014 Account (see Surface water streamflow summary for long-term mean monthly flow volumes).

Figure W3 Total monthly flow for the Murray River at Doctors Point (Albury) during the 2013–14 year compared with the long-term average and percentiles for the river

Source: Bureau of Meteorology.

For the Murray River system at Doctors Point (Albury), generally average monthly flows occurred for most of the 2013–14 year except for July 2013 and April to June 2014 (Figure W3). Inflows in the Murray River system in the 2013–14 year broadly followed the long term seasonal distribution. Dry catchments in the upper Murray system tributaries before winter 2013 resulted in poor responses to rain events in July 2013. From August 2013 to February 2014, inflows were slightly above or close to the long–term average. Although there were periods of above average rainfall in the MDB region (February to March 2014), these did not result in above average streamflow in the Murray River catchment, presumably because soil water stores were low after a relatively dry summer period.

Figure W4 Total monthly flow for the Darling River at Bourke during the 2013–14 year compared with the long-term average and percentiles for the river
Source: Bureau of Meteorology.

For the Darling River at Bourke, the 2013–14 year started with below average flows and continued throught out the year for the Darling River (Figure W4). Although there was a short period of above average rainfall in the region (February to March 2014), hardly any increase in streamflow volume across the Darling River catchment was observed, most likely because soil water stores and groundwater levels were very low after a very dry summer period.

Monthly flows in the Darling River were extremely low compared to the Murray River flows. As a result, the Northern Basin contribution to the water availability in the Southern Basin was almost negligible in the 2013-14 year.

Figure W5 Total monthly flow for the Ovens River at Peechelba during the 2013–14 year compared with the long-term average and percentiles for the river
Source: Bureau of Meteorology.

For the Ovens River at Peechelba streamflows were extremely high in the months of July and August. The Bureau of Meteorology had issued a flood warning in early August for the region for flooding that resulted in large monthly flow volume as seen in Figure W5. After a peak flow in August 2013, the monthly streamflows were below average until May 2014, before rising again to above average streamflow in June 2014. Although there were few periods of above average rainfall in the region (February–March 2014), these did not result in above average streamflow in the Ovens River catchment, presumably because soil water stores were low after a very dry summer period.

Major water initiatives

Commonwealth

In November 2013, the MDBA published its first constraints management strategy, Murray–Darling Basin Authority 2015b identifying priority constraints that will need to be addressed to enhance the benefits of environmental watering in some areas.

The new water trading rules came into effect on  1 July, 2014 (MDBA 2015c) MDBA will continue to work with the Basin states and irrigation infrastructure operators to ensure effective compliance of these rules.

The first Basin Environmental Water Outlook (MDBA 2015d) and second annual environmental watering priorities for the year ahead (2014–15) was released (MDBA 2015e).

The MDBA developed a method for estimating salt export from the River Murray system into the Southern Ocean. The Basin Plan includes a salt export objective (SEO) to ensure that adequate salt is flushed from the River Murray into the Southern Ocean. An early estimate indicates that salt export in 2013-14 was 0.7 million tonnes, bringing the three-year average to 1.5 million tonnes. This is less than the Basin Plan's objective of two million tonnes per year. However, flows over the barrages into the Coorong and low salinity levels in the River Murray indicate that some level of flushing has occurred. Salt interception schemes also diverted about 0.4 million tonnes of salt away from the river in 2013-14 (MDBA 2015j).

Two reviews of groundwater sustainable diversion limits were completed for New South Wales. The MDBA began review for the Goulburn-Murray Sedimentary Plain (MDBA 2015a).

Queensland

Work continued throughout the 2013-14 water year on development of the Warrego-Paroo-Nebine water resource plan package in preparation for accreditation under the Basin Plan.

South Australia

The following new surface water and groundwater resource water allocation plan (WAP) for the Eastern Mount Lofty Ranges (EMLR) was adopted on 17 December 2013 under the Natural Resources Management Act 2004. This plan covers the Eastern Mount Lofty Ranges prescribed area and incorporates the Angas Bremer prescribed wells area.

Eastern Mount Lofty Ranges Prescribed Water Resource Area water allocation plan (Government of South Australia 2014b).

Australian Capital Territory

The 2014 Account for the Canberra region includes information on major water initiatives applicable for the Australian Capital Territory.