Risk of Spill Information for the Murray system

Monday 11 October, 2021

Releases from Lake Hume continue to trigger spills from spillable water accounts in the Murray system. An update to the deductions from spillable water accounts will be made as part of the October 15 seasonal determination assessment.

Volume needed to fill Lake Hume at 1 October 2021: 77,975 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: July to September

 

Ranked historic unregulated inflow to Lake Hume
Ranked historic unregulated inflow to Lake Hume: July to September. Inflow for the July - September period is indicated by the red line: 1,584,570 ML

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

A bar graph titled Ranked historic inflow to Lake Hume: July – September 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 July – September 2021 period is indicated by the red line: 1,584,570 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 2,229,000 megalitres.

Tabulation of data from the image of the graph above.
% Probability of Exceedence 3 month inflow in megalitres (ML)
99% 67,800
90% 363,600 
80% 490,900 
70% 604,500 
60% 729,100 
50% 959,500 
40% 1,082,500 
30% 1,538,100 
2021 1,584,570
20% 1,679,000 
10% 2,229,000 
1% 3,580,400 

Ranked Historic Unregulated inflow to Lake Hume: October - December

Graph of ranked historic unregulated inflow to Lake Hume: October - December
The volume difference at Lake Hume between full supply and the storage volume on 1 October 2021 is indicated by the green line: 77,975 ML.

 

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

A bar graph titled Ranked historic inflow to Lake Hume: October – 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 October 2021 is indicated by the green line: 77,975 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 200,000 megalitres have a high probability of occurrence. Less than 10% probability of inflows above around 800,000 megalitres.

Tabulation of data from the image of the graph above.
% Probability of Exceedence 3 month inflow in megalitres (ML)
99% 5,600
Current Airspace 77,975
90% 252,600 
80% 419,400 
70% 531,000 
60% 606,400 
50% 682,100 
40% 803,900 
30% 946,300
20% 1,220,500
10% 1,581,120
1% 3,788,540

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). The first chart displays the volume of inflow to Lake Hume for the period 1 July to 30 September in each of those 128 years. The volumes of inflow shown are ranked in order from lowest to highest with the red line representing the volume of inflow recorded for the period in the current year (2021).

The second chart displays the volume of inflow to Lake Hume for the period 1 October to 31 December in each of the 128 years of historic data. The volumes of inflow shown are ranked in order from lowest to highest. The volume difference at Lake Hume between full supply and the storage volume on 1 October is indicated by the green line.

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.