Risk of Spill Information for the Murray system

Monday 10 January, 2022

Lake Hume is almost 99 per cent of capacity. Releases to manage the storage close to full supply have reduced in recent weeks but may need to recommence if inflows to the storage increase. An update to the deductions from spillable water accounts will be made as part of the December 15 seasonal determination assessment.

Volume needed to fill Lake Hume at 1 December 2021: 30,158 ML

The current volumes in Goulburn system spillable accounts is available at the  Victorian Water Register website.

Graph - Ranked Historic Unregulated Inflow to Lake Hume: September to November 

Ranked historic inflow to Lake Hume: September – November. Inflow for the September – November period is indicated by the red line: 1,480,970 ML

 

Description and Tabulation of the Graphical Content Unregulated Inflow to Lake Hume: September to November

A bar graph titled Ranked historic inflow to Lake Hume: September – November is on the page above. X axis label “% Probability of Exceedance” which spans 99% on the left to 1% on the right. Y axis label is “3 month inflow – units megalitres (ML)”. Significant highlighted data in the graph is the inflow for the September – November 2021 period is indicated by the red line: 1,480,970 ML.

Each % probability of exceedance is reported from 99% to 1%. The general nature of the information presented is low inflow values of less than 500,000 megalitres have a high probability of occurrence. Less than 10% probability of inflows above 1,935,800 megalitres.

Tabulation of data from the image of the graph above.
% Probability of Exceedance 3 month inflow in megalitres (ML)
99% 18,200
90% 355,400
80% 538,900
70% 698,000
60% 762,400
50% 948,600
40% 1,161,700
30% 1,322,300
2021 1,480,970
20% 1,588,600
10% 1,935,800
1% 3,141,600

Ranked Historic Unregulated inflow to Lake Hume: December

Description and Tabulation of the Graphical Content Unregulated Inflow to Lake Hume: December

A bar graph titled Ranked historic inflow to Lake Hume: December is on the page above. X axis label “% Probability of Exceedance” which spans 99% on the left to 1% on the right. Y axis label is “3 month inflow – units megalitres (ML)”. Significant highlighted data in the graph is the difference between the full supply volume of Lake Hume and the volume at 1 December 2021 is indicated by the green line: 30,158 ML.

Each % probability of exceedance is reported from 99% to 1%. The general nature of the information presented is low inflow values of less than 80,000 megalitres have a high probability of occurrence. Less than 10% probability of inflows above around 265,500 megalitres.

Tabulation of data from the image of the graph above.
% Probability of Exceedance 3 month inflow in megalitres (ML)
99% 0
90% 30,158
Current Airspace 48,440
80% 64,420
70% 84,400
60% 100,400 
50% 115,400 
40% 142,380 
30% 166,300
20% 212,100
10% 265,500
1% 481,580

Notes for charts:

The inflows to Hume are provided as a guide only with these inflows subject to state water sharing arrangements where inflows are shared 50:50 between Victoria and NSW.

There are 128 years of historic inflow data available for Lake Hume (inflow data for the period before the construction of the dam are based on modeled inflows).

Probability of exceedance: Probability that the volume of inflow will be equal to or greater than a specified volume in any given year.

Additional notes:

  • The information provided here for the Murray system does not take into consideration the State sharing arrangements for the Murray storages. Find the status of Victorian shares of Murray storages via theMDBA website.
  • The volumes in spillable water accounts can change due to seasonal determination increases. Active airspace management at Lake Hume could see reductions to Murray spillable water accounts prior to the storage reaching 100% capacity.
  • Current year inflows are based on operational data.