Calculation of the Choke opening balance

The operation of the Barmah Choke trade restriction is specified in the Permissible Transfers between Trading Zones Protocol 2010 (Permissible Transfers Protocol). The opening balance for the Choke water account on 1 July is based on the Snowy water savings that were realised downstream of the Choke in the previous water year and reflected in allocations against the Entitlement Record.

The Permissible Transfers Protocol defines the Entitlement Record that is used in calculating the opening balance for the water year. The Entitlement Record lists the water entitlements created to hold the Snowy water savings that reduce the demand across the Choke

The Entitlement Record and the calculation of the opening balance for 2020–21, as an example, is shown in Table 1 below. The opening balance is calculated as the Entitlement Record multiplied by the allocations made against these entitlements in the previous water year.

Table 1: The Entitlement Record and example calculation of the Choke opening balance for 2020–21

* HRWS – high reliability water shares, LRWS – low reliability water shares

Calculation of the Entitlement Record

The treatment of Snowy water savings in regard to accounting for trade through the Choke is set out in Clauses 7 and 8 of the Permissible Transfers Protocol.

Savings made downstream of the Choke to provide Snowy River Increased Flows (SRIF), after 1 July 2007, are included on the Entitlement Record. Savings made downstream of the Choke to provide River Murray Increased Flows (RMIF) are treated as pre-existing entitlements which must still be delivered downstream of the Choke and therefore are not included on the Entitlement Record.

The first 210 gigalitres (GL) of water savings is shared one-third as RMIF and two-thirds as SRIF. Savings in excess of 210 GL are all SRIF.

The rules for establishing the Entitlement Record are:

1. Water savings made upstream of the Choke are not included in the Entitlement Record.
2. Water savings made downstream of the Choke before 1 July 2007 are not included in the Entitlement Record.
3. For water savings made downstream of the Choke after 1 July 2007:
   1. two-thirds of the volume of entitlement created for the first 210 GL of savings is added to the Entitlement Record, and
   2. the whole volume of entitlement created for savings in excess of 210 GL is added to the Entitlement Record.

Background to the Snowy water savings can be found on the NSW Department of Planning, Industry and Environment website.