Risk of Spill Information for the Campaspe system

Thursday 15 February, 2024

An update to the deductions from spillable water accounts was made as part of the February 15 seasonal determination assessment.

The risk of spill in the Campaspe system at 1 February 2024: 50%
This value represents the percentage of years that spills occur from GMW’s share of Lake Eppalock 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 Eppalock at 1 February 2024: 500 ML

Click here to find the current volumes in Campaspe system spillable water accounts.

Ranked historic inflow to Lake Eppalock: Nov - Jan

Ranked historic inflow to Lake Eppalock

Ranked historic inflow to Lake Eppalock: Nov – Jan 2024. Inflow for the Nov – Jan 2024 period is indicated by the red line: 61,530 ML

Description and Tabulation of the graphical content inflow to Lake Eppalock: Nov - Jan

A bar graph titled Ranked historic inflow to Lake Eppalock: Nov - Jan 2024 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 Nov - Jan 2024 period is indicated by the red line: 61,530 ML.

Each % probability of exceedance is reported from 99% to 1%. Inflow values of greater than 300 megalitres have a high probability of occurrence, i.e. > 90%. There is less than 10% probability of inflows above 33,000 megalitres.

Tabulation of data from the image above of the graph

% probability of exceedance 3 month inflow in megalitres
99% 0
90% 314
80% 1,271
70% 2,353
60% 3,224
50% 4,942
40% 7,064
30% 9,072
20% 15,900
10% 33,660
2023/24 61,530
1% 258,646

 

Ranked Historic inflow to Lake Eppalock: February - June

Ranked historic inflow to Lake Eppalock

Ranked historic inflow to Lake Eppalock: August – December. The difference between the full supply volume of Lake Eppalock and the volume at 1 August 2023 is shown by the green line: 500 ML

Description and Tabulation of the graphical content inflow to Lake Eppalock: February - June

A bar graph titled Ranked historic inflow to Lake Eppalock: August – 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 Eppalock and the volume at 1 February 2024 is indicated by the green line: 500 ML.

Each % probability of exceedance is reported from 99% to 1%. Inflow values of greater than 400 megalitres have a high probability of occurrence, i.e. > 90%. There is less than 10% probability of inflows above 82,000 megalitres.

Tabulation of data from the image above of the graph

% probability of exceedance 3 month inflow in megalitres
99% 0
90% 407
Current airspace 500
80% 1,617
70% 2,991
60% 5,165
50% 11,430
40% 17,724
30% 24,127
20% 46,301
10% 82,557
1% 187,806

Notes for charts:

There are 132 years of historic inflow data available for Lake Eppalock (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 Eppalock for the period 1 November to 31 January in each of those 132 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 water year (2023/24).

The second chart displays the volume of inflow to Lake Eppalock for the period 1 February to 30 June in each of the 132 years of historic data. The volumes of inflow shown are ranked in order from lowest to highest. The volume difference at Lake Eppalock between full supply and the storage volume on 1 February 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 second chart, the probability that inflows to Lake Eppalock from 1 February to 30 June will be greater than 40,000 ML in any given year is close to 20%.

Additional notes:

  • The volumes in spillable water accounts can change due to seasonal determination increases.
  • The information provided here for the Campaspe system does not take into consideration the storage sharing arrangements at Lake Eppalock between GMW and Coliban Water.
  • Current year inflows are based on operational data.