(3) To assess current long-term average annual extraction from this water source the model referred to in clause 31 (1) shall be set to represent as closely as possible all water use development, supply system management and other factors affecting the quantity of long-term average annual extraction from this water source at the time of compliance assessment.
45 The model used to carry out these functions is known as the Gwydir IQQM. The evidence is that the model allows assessments to be made regarding the river flows and water extractions that would have occurred in the Gwydir river source if the level of water use, development, volume of licences and rules affecting water access had been in place and consistent over the period for which historical climatic data is available. In the case of long-term average annual extractions, the IQQM model assumes that conditions in the Gwydir river source have always been exactly as they are today and applies that to the available climatic data since the 1890's.
46 In the case of the long-term extraction limit established pursuant to cl 30(1)(a) of the plan, the model assumes development levels at 1999/2000. The Cap dictated by Sch F to the Murray-Darling Basin Agreement assumes development levels at 1994.
47 The Minister relies on the following statement in the SWMOP to refute the applicant's claim that the Cap fails to take account of environmental issues:-
Evidence of significant environmental damage and continuing erosion of supply reliability to downstream users led the Murray-Darling Basin Ministerial Council (MDBMC) to place a cap on water extractions in the Basin at 1993/94 development levels (the MDBMC Cap).
However, there is scientific evidence to suggest that water extractions at the Cap level may be responsible for unacceptable degree of environmental damage in parts of the Basin and a lower extraction limit may be required to rehabilitate these water sources and ensure the effectiveness of the environmental water rules. The extraction limit target for the NSW regulated rivers of the Murray-Darling Basin is therefore set at a level of extraction below the MDBMC Cap, which results from the impact of the prevailing environmental water rules.
This lower extraction limit is necessary to ensure that river flows not specifically targeted or restored by environmental water rules cannot be further diminished by extractions. Because the extraction limit is below the Cap it ensures this external obligation is also met.
48 It is contended by the respondent that the setting of the lower of two averages by cl 30(1) as the long-term extraction limit recognises that the Cap was not necessarily environmentally adequate. Furthermore, as s 6(3) requires the SWMOP to be consistent with, inter alia, the Murray-Darling Basin Agreement, s 8 must have been enacted on the basis that the Cap "could be caught within s 8". For those reasons, it is submitted by Mr Hutley, on behalf of the Minister, that the word "water" where used in s 8, is sufficiently broad to catch the rather abstract concept erected by cl 14.
49 It is difficult to comprehend how the respondent's argument can jump from an acceptance that cl 14(a) and cl 14(b) do not create, commit or otherwise operate as a rule that sets aside a specific body, volume or other identifiable portion of the water within the water source to a point where it is claimed the same clauses operate as a rule that does in fact establish and identify the class of environmental water recognised by s 8 as environmental health water.
50 The following note appears after cl 14(b) of the plan:-
Note. By limiting long term average annual extractions to an estimated 388,000 megalitres per year this Plan ensures that approximately 56% of the long-term average annual flow in this water source (estimated to be 875,400 megalitres per year) will be preserved and will contribute to the maintenance of basic ecosystem health.
51 Irrespective of the veracity of the statement in the note, it is expressly provided by cl 5(3) of the plan that notes in this plan do not form part of the plan, although the effect of terms used may be explained by the notes by dint of cl 5(1).
52 Moreover, the statement that limiting the long-term average annual extraction to 388,000 megalitres ensures that approximately 56 per cent of the long-term average annual flow will be preserved has the potential to be as difficult to understand, in practical terms in the context of one water year, as attempting to describe what physically happens in any one year by reference to the long-term extraction limit or, for that matter, the long-term average annual extraction. Nevertheless, the question might still be asked whether the provisions of cl 14 can amount to a rule within the meaning of s 8(2) even if minds differ as to their potential to be effective.
53 Spread over time, the concept of the plan appears to be to constrain extractions to a particular average level thereby maintaining an average balance of water and leaving it uncommitted to any other purpose except to remain in the system, thereby theoretically preserving it as environmental water in the long-term. Clause 32 then has the effect of maintaining the average volume by reducing other water determinations whenever the current long-term average annual extraction exceeds the volumes in cl 30(1)(a) or (b).
54 The environmental water is in that way identified as that average volume which is the difference between the long-term extraction limit and the long-term average flow. It is established as an average volume calculated using the results of the assessments made pursuant to cl 31 of the plan. Clause 32 ensures the average volume committed is maintained by adjusting other entitlements until the current long-term average annual extraction from the water source is made to equate to the long-term extraction limit. Even though the period over which the average is to be calculated is left at large by the plan, so too are other inputs to the hydrolic computer model. Nonetheless, the model is described in general terms as the one "that at the time, is approved by the Department for assessing long-term water use from this course". Dictating the inputs to such a model should not, and probably cannot, be achieved through an instrument such as a water sharing plan. The extent of variables to be taken into account in respect of climate alone is recognised by the combined effect of s 20(2)(c) and s 20(1)(e) or s 20(1)(a), (b), (c) and (d). Arguably, therefore, if a fixed period was designated by the plan, say 10 years, vital information obtained in respect of an earlier period could be excluded. The evidence is that the model can be set up to assess the river flows and volume of water extractions that would have occurred each year since the 1890's had the current rules and current level of development been in place at that time. As further information becomes available, in any respect, that contributes to a more accurate undertaking of how the Gwydir system operates it can be used to assess the long-term extraction limit.
55 That the period of an assessment will not be constant is highlighted by the definition in cl 31of "long-term average annual extraction" as the average of annual water extraction from the water source over the period for which an assessment is carried out. Alternatively, cap baseline conditions are separately determined as those used for assessment of Cap in Sch F of the Murray-Darling Basin Agreement.