An update to the deductions from spillable water accounts was made as part of the July 1 seasonal determination assessment.
The risk of spill in the Goulburn system at 1 July 2024: 80%
This value represents the percentage of years that spills occur from Lake Eildon taking into account the current storage volume, storage releases, inflows and evaporation from the storage using the historic data available.
Note: 10% or lower is the threshold for a declaration that would return water quarantined in spillable water accounts to allocation bank accounts.
Volume needed to fill Lake Eildon at 1 July 2024:382,700 ML
Click here to find the current volumes in Goulburn system spillable water accounts.
Ranked historic inflow to Lake Eildon: Apr - Jun
Description and Tabulation of the graphical content inflow to Lake Eildon: April - June
A bar graph titled Ranked historic inflow to Lake Eildon: April - June 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 April - June 2024 period is indicated by the red line: 66,954 ML.
Each % probability of exceedance is reported from 99% to 1%. The general nature of the information presented is inflow values of greater than 61,505 megalitres have a high probability of occurrence (i.e. > 90%). Less than 10% probability of inflows above 500,000 megalitres.
Tabulation of data from the image above of the graph
99% |
40,341 |
90% |
61,505 |
2024 |
66,954 |
80% |
78,159 |
70% |
94,205 |
60% |
111,714 |
50% |
163,325 |
40% |
184,271 |
30% |
244,336 |
20% |
322,170 |
10% |
497,279 |
1% |
932,212 |
Ranked historic inflow to Lake Eildon: July - December
Description and Tabulation of the graphical content inflow to Lake Eildon: July - December
A bar graph titled Ranked historic inflow to Lake Eildon: July – 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 Eildon and the volume at 1 July 2024 is indicated by the green line: 382,700 ML.
Each % probability of exceedance is reported from 99% to 1%. The general nature of the information presented is inflow values of greater than 500,000 megalitres have a high probability of occurrence (i.e. > 90%). Less than 10% probability of inflows above 1,867,000 megalitres.
Tabulation of data from the image above of the graph
99% |
130,745 |
Current airspace |
382,700 |
90% |
517,309 |
80% |
680,856 |
70% |
817,127 |
60% |
958,680 |
50% |
1,066,171 |
40% |
1,224,797 |
30% |
1,400,262 |
20% |
1,631,750 |
10% |
1,867,818 |
1% |
2,362,314 |
Notes for charts:
There are 133 years of historic inflow data available for Lake Eildon (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 Eildon for the period 1 May to 31 July in each of those 133 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 (2024).
The second chart displays the volume of inflow to Lake Eildon for the period 1 July to 31 December in each of the 133 years of historic data. The volumes of inflow shown are ranked in order from lowest to highest. The volume difference at Lake Eildon between full supply and the storage volume on 1 July 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. For example, in the first chart above, the probability that inflows to Lake Eildon from 1 April to 30 June will be greater than 200,000 ML in any given year is ~40%.
Additional notes:
- The volumes in spillable water accounts can change due to seasonal determination increases, provided there has been no low risk of spill declaration made
- Operation to target filling arrangements at Lake Eildon could see reductions to spillable water accounts prior to the storage reaching the full supply level.
- Current year inflows are based on operational data.