How Seasonal Determinations Work

Making Seasonal Determinations

Victoria's water allocations are determined using a water budget. The Resource Manager manages seasonal determinations on behalf of all entitlement holders and regularly reviews the water budget calculations.

The water budget calculates how much water is in the dams and the expected inflows over a planning period to decide how much water can be allocated.

We cannot allocate more than the water available over the budget period.

Photograph of a channel Aerial photograph of the dam wall of Lake Eildon


Available water in the budget is used to meet commitments including losses from storages, rivers and channels, as well as water available in entitlement holders' accounts, including current season allocations and water carried over. Water continues to be allocated to entitlement holders until seasonal determinations reach 100% of high-reliability water shares (HRWS).  

In the Goulburn, Murray, Campaspe and Loddon systems if full allocation to high-reliability entitlements is possible (i.e. the seasonal determination is 100% HRWS), the water budget is calculated over a two-year period. This means inflows and commitments to the end of the following season are considered. This is to make sure reserves are established to secure the availability of high-reliability entitlements in the following year if conditions turn dry.

Victoria's allocation policy has always been to secure next year's allocation of high-reliability entitlements before making seasonal determinations to low-reliability entitlements. The security of our high-reliability entitlements has supported the development of high-value irrigated agriculture in Victoria.

In the Broken and Bullarook systems once 100% high-reliability is achieved, additional resource is attributed to increasing allocation of low-reliability entitlements, up to 100% of low- reliability.

  Please click here for schematic showing how seasonal determinations are made.

Conditions Needed to Make a Low-Reliability Seasonal Determination

Looking at the level of the dams, many people are wondering what conditions are needed to allocate to low-reliability entitlements. In simple terms, there are two key things that play an important role:

1. Having good reserves in the dams to start the year.

If there has been a low-reliability seasonal determination the previous year, then you will know that full reserves for allocation to high-reliability entitlements have been secured, and there is a good foundation for possible allocation to low-reliability entitlements this year.

2. Good inflows in the current season.

Most importantly, good inflows in the current season will determine whether a low-reliability seasonal determination can be announced. With good inflow allocation to low-reliability entitlements can be possible even if we do not start the year with full reserves.

All inflows improve the water budget. Inflows upstream of the dams increases the water available in storage, and inflows below the dams can be used to reduce commitments by covering river and channel losses and meeting early season use.

Water from other sources is also important in providing extra water that supports seasonal determinations to low-reliability entitlements.

For further information about the availability of low-reliability entitlements please click here.