New South Wales Consolidated Regulations

WATER SHARING PLAN FOR THE LACHLAN REGULATED RIVER WATER SOURCE 2003 - REG 15

15 Planned environmental water

(1) This Plan establishes the following planned environmental water rules for the management of translucent releases from Wyangala Dam water storage:

(a) translucent releases may be made from Wyangala Dam during the period 15 May to 15 November, only if the inflows to Wyangala Dam water storage since 1 January that calendar year have exceeded 250,000 megalitres,

(b) translucent releases under subclause (1) (a) are to be made when the combination of Wyangala Dam inflows plus downstream tributary inflows would be sufficient to produce a flow downstream of Lake Brewster of greater than:

(i) 4,000 megalitres per day (hereafter "ML/day") when the volume of water held in Wyangala Dam water storage is less than or equal to 50% of the full supply volume, or

(ii) 3,500 ML/day when the volume of water held in Wyangala Dam water storage is more than 50% of the full supply volume,

(c) the translucent release from Wyangala Dam is to be the lesser of the inflow to Wyangala Dam water storage and the release necessary to achieve a flow at Lake Brewster Weir of :

(i) 4,000 ML/day plus 25 ML/day for each 1% by which the volume of water held in Wyangala Dam water storage exceeds 0% of the full supply volume, when the volume of water held is less than or equal to 50% of the full supply volume,

(ii) 3,500 ML/day plus 31.25 ML/day for each 1% by which the volume of water held in Wyangala Dam water storage exceeds 0% of the full supply volume, when the volume of water held is greater than 50% of the full supply volume but less than or equal to 80% of the full supply volume, and

(iii) 6,000 ML/day plus 100 ML/day for each 1% by which the volume of water held in Wyangala Dam water storage exceeds 80% of the full supply volume,

Note: Subclause (1) (c) (iii) results in the maximum release from Wyangala Dam when it is full being the release necessary to achieve a flow at Lake Brewster Weir of 8000 ML/day.

(d) translucent releases under subclause (1) (a) are only to be made when the sum of flows that have passed downstream of Lake Brewster Weir (measured at Brewster Weir) since the 1 June of that year are less than 350,000 megalitres plus the sum of the following over the same period:

(i) downstream water orders and any losses associated with delivery of these water orders,

(ii) replenishment flows to effluent rivers downstream of Lake Brewster Weir and any losses downstream of Lake Brewster Weir associated with delivery of these replenishment flows,

(iii) any flow volume downstream of Lake Brewster Weir resulting from airspace releases under clause 65, and

(iv) any flow volume downstream of Lake Brewster Weir resulting from releases made pursuant to 15 (2) (c) or 15 (3) (c),

(e) tributary inflows occurring at any time that the translucent releases conditions under subclauses (1) (a), (1) (b) and (1) (d) are satisfied are not to be used for extractive purposes or diverted to, or stored in, any weirs or water storages except to the extent that they are in excess of the flow required to satisfy the flow rate downstream of Lake Brewster that results from the calculation in subclause (1) (b),

Note: If flows are insufficient to satisfy subclause (1) (b), or the conditions specified in subclauses (a) or (d) are not met, tributary inflows may be diverted and stored in Lake Cargelligo or Lake Brewster, consistent with normal operational management.

(f) water flows required to meet translucent release flow targets in subclause (1) (c) are not to be taken or used for any other purpose,

(g) releases of water from Lake Cargelligo and Lake Brewster may be substituted for all or part of the translucent releases from Wyangala Dam specified in this clause if making the translucent releases from Wyangala Dam is likely to cause flooding,

(h) water released in accordance with subclause (1) (g) from Lake Brewster shall be accounted for as flow passing downstream of Lake Brewster Weir under subclause (1) (d), and

(i) in the event that the release capacity of Wyangala Dam is insufficient to provide the release as specified in subclause (1) (c) plus the releases required to satisfy access licence orders, then:

(i) releases are to equal the release capacity,

(ii) water is to be permitted to be taken in accordance with access licence water orders,

(iii) the portion of the required translucent release which has not been supplied is to be calculated as the total release minus the release made to satisfy access licence holder demands,

(iv) the volumes calculated under subclause (1) (i) (iii) are to be accrued and released at the earliest opportunity, and

(v) releases under subclause (1) (i) (iv) are not to be subject to the requirements of subclauses (1) (a), (1) (b) and (1) (c).

(j) a review of the requirement, in subclause (1) (a), that inflows to Wyangala Dam water storage since 1 January in a calendar year must have exceeded 250,000 megalitres before translucent releases may be made, is to :

(i) be carried out by the Minister before the end of year 5 of this Plan, and

(ii) assess the environmental and socio-economic impacts of reductions in the required volume of inflow, and

(k) subclause (1) (a) may be varied under section 45 (1) (b) of the Act and as set out in Part 14 of this Plan.

(2) This Plan establishes the following planned environmental water rules for the management of an environmental contingency allowance held in Wyangala Dam water storage (hereafter "the WECA") and management of an environmental contingency allowance held in Lake Brewster (hereafter "the LBECA"):

(a) accounts of the water credited to and released from the WECA and LBECA are to be kept,

(b) 10,000 megalitres is to be credited to the WECA account and 10,000 megalitres is to be credited to the LBECA account:

(i) on 1 July each year, if the total volume of water in the water allocation accounts of regulated river (general security) access licences exceeds 50% of the total volume of regulated river (general security) access licence share components, or

(ii) if no crediting under subclause (2) (b) (i) occurred on 1 July of that water year, when the sum of the volume of water in the water allocation accounts of regulated river (general security) access licences at 1 July, plus the volume of water provided by available water determinations for those licences during the water year, is equivalent to 75% of total regulated river (general security) share components,

(c) water credited to the WECA and LBECA accounts may be released for ecological purposes, including, but not limited to, completion of waterbird breeding events, promotion of fish breeding, promotion of fish passage, wetland watering and increasing flow variability,

(d) rules determining the volume and timing of releases of water credited to the WECA and LBECA accounts shall be specified in accordance with procedures established by the Minister,

(e) the volume of LBECA available for release from Lake Brewster at any time shall be the lesser of the volume of credit remaining in the LBECA account and the active storage in Lake Brewster, and

(f) any credits remaining in the WECA and LBECA accounts are to be forfeited at the end of each water year.

Note: It is not possible to forecast when releases of water from the WECA and LBECA will be required, as releases occur in response to unpredictable environmental circumstances. To allow estimation of the effect of the WECA and LBECA rules on water extractions computer modelling has assumed that a total of 5,000 megalitres of WECA and of LBECA were released at the end of each years when there was water in the accounts. It is expected that, over the life of the Plan average releases from each account would not exceed these figures.

(3) This Plan establishes the following planned environmental water rules for the management of a water quality allowance (hereafter "the WQA"):

(a) an account of the water credited to and released from the WQA is to be kept,

(b) 20,000 megalitres is to be credited to the WQA account on 1 July each year,

(c) water credited to the WQA may be released for any water quality management purpose, but in particular for reduction of salinity levels and mitigation of blue-green algae impacts,

(d) rules determining the volume and timing of releases of water credited to the WQA account shall be specified in accordance with procedures established by the Minister, and

(e) any credits remaining in the WQA accounts are to forfeit at the end of each water year.