Welcome to another update on River Murray operations. Make sure you grab a copy of the full weekly report as it includes important information about Lock 9 closing for maintenance for up to 12 weeks.
MDBA active storage increased again this week, rising by 104 GL to 7,520 GL (87%). At Dartmouth Reservoir, the storage volume increased by 9 GL to 3,209 GL (83% capacity). The release remains at the normal minimum of 200 ML/day. At Hume Reservoir, the storage volume increased by 17 GL to 2,626 GL (87% capacity). The release from Hume Dam was increased slightly during the mid part of the week in response to the dry weather and slightly higher late season irrigation demands. The current target downstream of the dam is 7,300 ML/day at Doctors Point, however with irrigation diversions at the main extraction points scheduled to drop away as the season draws to an end, releases at Hume can be expected to be decreased in the coming days.
At Lake Mulwala, the pool level is currently 124.67 m AHD or 23 cm below full supply. Diversions have averaged 3,500 ML/day at Mulwala Canal and 600 ML/day at the Yarrawonga Main Channel. Irrigation diversions from the lake are expected to be completed for the season by the end of next week. Release from Yarrawonga Weir is currently 6,000 ML/day and is expected to be decreased by about 300 ML/day over the coming days.
At the Edward River and Gulpa Creek offtakes, diversions have reduced slightly over the past week. A further reduction in flow towards the seasonal minimums will take place over the next few weeks if dry conditions persist. At Stevens Weir, the pool level is currently 4.67 m and the downstream flow is 1,500 ML/day. The release is broadly expected to decrease over the coming weeks although small temporary rises in flow may occur as the end of season drainage of irrigation channels results in return flows back to the river. Further downstream, flows continue to recede on all gauges along the lower Edward-Wakool system. At Kyalite, the flow has dropped back to around 5,000 ML/day.
On the Goulburn River, the flow at McCoys has remained above 6,000 ML/day for most of the week, however a recession in flows has now been observed and, without reasonable rainfall, the flow should continue to fall away over the coming week. At Torrumbarry Weir, the flow dipped below 10,000 ML/day mid-week as expected, however the river has since increased to a flow of 10,200 ML/day with the addition of higher flow from the Goulburn. The flow is now expected to drop back towards 9,000 ML/day with National Channel diversions increasing to 3,100 ML/day before the irrigation season finishes next week.
On the Murrumbidgee River, the flow at Balranald has continued to fall away after the recent flood peak. The current flow is 18,000 ML/day and should be below 15,000 ML/day sometime next week.
At Euston, the Murray continues to recede slowly, with the current flow at 34,200 ML/day. Flows below 30,000 ML/day are not expected until the middle of next week.
On the Darling River, flows continue to fall away upstream of Menindee Lakes. At Bourke, the flow has now receded for about 9 weeks since the 237,000 ML/day flood peak in early March. The current flow is now 3,600 ML/day and with conditions typically staying dry in the northern Basin during the winter months, the flow should continue to slowly drop away. At Menindee Lakes, inflows have held on well as flood water drains back in off the Darling River and Talyawalka Creek flood plains. Average inflows during the week decreased from 49,000 to 35,000 ML/day and will continue falling away over the coming weeks. The combined volume of the lakes increased by a further 82 GL this week, and the total storage of 2,009 GL (116%) is just below the full surcharge level. Release from Menindee (measured at Weir 32) has been held at around 19,000 ML/day, but may be decreased during the coming week if the inflow recession allows.
Downstream on the lower Darling, the flow at Burtundy has remained steady at just under 20,000 ML/day throughout the week at what appears to be a broad peak. For further information on the flood operations at Menindee Lakes, please refer to the NSW Office of Water website.
At Wentworth, flows have also remained steady during the week and the pool level is 21 cm above the normal operating level. The flow is currently just under 58,000 ML/day, but has begun what is expected to be a long recession over coming weeks. Downstream at Lock 9, essential maintenance, scheduled to begin on 21 May will result in the lock being closed for 12 weeks. (See the media release in the full weekly report for further details).
At Lake Victoria, the storage volume decreased by 4 GL to 350 GL (52%) and the flow to South Australia averaged 55,000 ML/day.
Downstream at Lock 1, the flow remains above 50,000 ML/day delivering high inflows to the Lower Lakes and into the Coorong. At the Barrages, operations continue to pass high flows, whilst managing short periods of reverse head (when downstream level due to tide and storm surge may exceed upstream level). There were high tides again over the last week, however favourable weather conditions meant a number of Barrage gates at Goolwa and Mundoo could be left opened, with gates at Mundoo closed down for a few hours on several days during high tide. Lake levels remained relatively steady with the 5 day average level for Lake Alexandrina at 0.71 m AHD. Forecast weather and swell conditions mean gates at Goolwa and Mundoo may be closed for several days this week.