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Catchwords: EVIDENCE — Advance rulings — Whether appropriate to exercise discretion to make an advance ruling in relation to joint expert reports — Advance ruling appropriate in all the circumstances
EVIDENCE — Opinion evidence — Exceptions — Joint expert reports — Whether experts had adequately exposed their path of reasoning — Where experts did not adequately identify assumptions relied upon — Where the reasoning process of the experts leading to the formation of their opinions is not adequately exposed — Joint expert reports ruled inadmissible

Legislation Cited: Evidence Act 1995 (NSW), ss 56, 79, 192A
Water Management (General) Amendment Regulation 2021 (NSW), cll 23G-J
Water Management (General) Regulations 2018 (NSW), cll 23A-23L
Water Management Act 2000 (NSW), ss 56, 57A
Water Sharing Plan for the Barwon-Darling Unregulated River Water Source 2012 (NSW)
Water Sharing Plan for the Macquarie and Cudgegong Regulated Rivers Water Source 2016 (NSW)

Cases Cited: Australian Securities and Investments Commission, Re Whitebox Trading Pty Ltd v Whitebox Trading Pty Ltd [2017] FCA 324
Bailey v Director-General, Department of Natural Resources [2013] NSWSC 515
Beslic v MLC Ltd [2015] NSWSC 908
Budvalt Pty Ltd v The Minister for Lands and Water; Hospitality and Racing, the Minister for Administering the Water Management Act 2000 [2025] NSWSC 609.
Coastal Service Centres Pty Ltd v United Petroleum Pty Ltd [2020] NSWSC 1870
Emu Rider Pty Ltd ATF the trustee for Griffiths Investment Trust v Minister administering the Water Management Act 2000 [2025] NSWLEC 64
Gondarra v Minister for Families, Housing, Community Services and Indigenous Affairs (2012) 127 ALD 288; [2012] FCA 185
Herron v HarperCollins Publishers Australia Pty Ltd (2022) 292 FCR 336; [2022] FCAFC 68
Lambert Leasing Inc v QBE Insurance Australia Ltd [2012] NSWSC 953
Menz v Wagga Wagga Show Society Inc (2020) 103 NSWLR 103; [2020] NSWCA 65
NA & J Investments Pty Ltd v Minister Administering the Water Management Act 2000 (No 4) [2012] NSWLEC 120
Ocean Marine Mutual Insurance Association (Europe) OV v Jetopay Pty Ltd (2000) 120 FCR 146; [2000] FCA 1463
Owners – Strata Plan No 90189 v Parkview Constructions Pty Ltd [2022] NSWSC 1382
Ramsay v Minister for Lands and Water; Hospitality and Racing, The Minister Administering the Water Management Act 2000 [2023] NSWCA 299
Ramsay v The Minister for Lands and Water; Hospitality and Racing, The Minister administering the Water Management Act 2000 [2023] NSWLEC 66
Risk v Northern Territory [2006] FCA 404
Searle v Commonwealth (No 5) [2022] NSWSC 119
Southern Cross Airports v Chief Commissioner of State Revenue [2011] NSWSC 349
Sydney Attractions Group Pty Ltd v Schulman [2012] NSWSC 951
Sydneywide Distributors Pty Ltd v Red Bull Australia Pty Ltd (2002) 234 FCR 549; [2002] FCAFC 157
TKWJ v The Queen (2002) 212 CLR 124; [2002] HCA 46
Trusted Cloud Pty Ltd v Core Desktop Pty Ltd [2015] FCA 33
Wadsworth v Hamilton [2022] NSWSC 396

Category: Procedural rulings

Parties: In 2023/00300385:
David Burnett Ramsay (plaintiff)
Minister for Lands and Water; Hospitality and Racing, the Minister administering the Water Management Act 2000 (defendant)
In 2023/00302455:
Alexander David Ramsay (first plaintiff)
Annette Yvonne Ramsay (second plaintiff)
Minister for Lands and Water; Hospitality and Racing, the Minister administering the Water Management Act 2000 (defendant)

Representation: Counsel:
C Ireland (plaintiffs)
N Sharp SC with A Bell (defendant)
Solicitors:
Horton Rhodes Legal (plaintiffs)
NSW Department of Climate Change, Energy and the Environment (defendant)

File Number(s): 2023/00300385
2023/00302455

Publication restriction: Nil

JUDGMENT

1. By notice of motion dated 4 June 2026 filed in both proceedings (noting that the notice of motion fails to identify the joint expert report for Banchory dated 17 September 2024), the Minister administering the Water Management Act 2000 (Minister) seeks an advance ruling pursuant to s 192A of the Evidence Act 1995 (NSW) on the admissibility of several joint expert reports in the two substantive proceedings, which are being heard concurrently. The Minister also seeks leave to file additional lay evidence as well as an expert report. The notice of motion is opposed by the plaintiffs in the substantive proceedings.

2. The subject matter of the litigation and the proceedings themselves have a lengthy and somewhat unusual history, some of which is outlined in a decision of the Court of Appeal in Ramsay v Minister for Lands and Water; Hospitality and Racing, The Minister Administering the Water Management Act 2000 [2023] NSWCA 299. Those appellate proceedings involved the same parties as in the current proceedings. Mr David Burnett Ramsay is the owner of a property near Warren called “Banchory”. Mr Alexander David Ramsay and his wife, Mrs Annette Yvonne Ramsay, are the owners of another property near Warren called “Flintrock” (without disrespect I shall refer to them collectively as “the Ramsays”). Both properties are located on a floodplain and are subject to the Water Sharing Plan for the Macquarie and Cudgegong Regulated Rivers Water Source 2016 (NSW).

3. As long ago as 2014, the Ramsays registered their interest with the Minister in obtaining what are known as “access licences”. By s 56 of the Water Management Act 2000 (NSW) (WM Act), such licences would entitle the Ramsays to use a particular share of the available water within their respective water management area. The Ramsays were interested in obtaining what are known as “replacement floodplain harvesting (regulated river) access licences” (FH licences). Such licences are provided for by s 57A of the WM Act and cll 23A-23L of the Water Management (General) Regulations 2018 (NSW) (WM Regulations).

4. The Ramsays were told in March 2015 of their preliminary draft eligibility to be issued with FH licences. There was then an extensive exchange of correspondence between the Ramsays and the Department of Planning and Environment on the share components of the proposed FH licences. In mid-2022, the Ramsays were told an FH licence with a share component of 4,041 unit shares would be issued in respect of Banchory and an FH licence with a share component of 2,883 unit shares would be issued in respect of Flintrock (1 unit equals 1 ML of water). The parties exchanged further correspondence concerning the proposed share component determinations.

5. In early September 2022 the Ramsays were informed that the proposed share component for Banchory would be reduced to 3,926 unit shares and to 2,522 unit shares for Flintrock.

6. The Department’s modelling which produced those figures was criticised by the Ramsays, who claimed that the share entitlements for Banchory should exceed 8,000 units, while the share entitlement for Flintlock should exceed 7,500-8,000 units.

7. On 10 February 2023, the Minister informed the Ramsays that determinations had been made under s 57A of the WM Act and cl 23K of the WM Regulations so as to issue an FH licence for Flintrock with a share component of 2,522 unit shares and an FH licence in respect of Banchory with a share component of 3,926 unit shares. In determining the share components, the Minister was obliged by cl 23B(5) of the WM Regulations to use the three models which had to be adopted under cl 23G(1), namely:

(a) the current conditions model; (b) the eligible water supply works scenario model (eligible works model); and (c) the plan limit compliance scenario model.

8. The Ramsays challenged the merits of those determinations in early 2023 by commencing Class 1 proceedings in the Land and Environment Court. On 26 June 2023, Pain J summarily dismissed those applications, holding that the Ramsays did not have a merits appeal right in respect of the determinations (see Ramsay v The Minister for Lands and Water; Hospitality and Racing, The Minister administering the Water Management Act 2000 [2023] NSWLEC 66).

9. That decision was unsuccessfully challenged by the Ramsays in the Court of Appeal, resulting in the Ramsay decision referred to at [2] above.

10. On 21 and 22 September 2023, the Ramsays commenced judicial review proceedings in this Court concerning the determinations relating to both Banchory and Flintrock respectively.

11. Orders were made on 14 December 2023 for both proceedings to be heard concurrently.

12. Similarly worded amended summonses (in narrative form) were filed in both proceedings on 30 January 2024, challenging the determinations on several grounds, including jurisdictional error and jurisdictional fact. The amended summons relating to Banchory raises the following grounds:

Grounds

The recent known levels of irrigation on Banchory support a share entitlement for Banchory of 8,000 ML (or 8,000 unit shares).

The Department was advised of this fact in the submission of 6 October 2022.

It follows that the calculation of the share component of 3,926 unit shares for the Banchory Access Licence was calculated contrary to the evidence and factual material before the Department and contrary to the facts.

In addition, this factually incorrect calculation demonstrates that the model used to determine the estimated volume of water capable of being used by a landholder’s eligible water supply works for the water source, and by all eligible water supply works for the water source (the Eligible Works Model) has either been misapplied or applied by an erroneous process to Banchory, or is itself in error.

Division 2 of Part 2A of the Regulation requires the modelling of the landowner’s estimated volume of water capable of being used by the landowner’s eligible water supply works and the Eligible Works Model to provide or produce a reasonable estimate of the water capable of being used by the landowner’s eligible water supply works and to be reasonably accurate and correct.

The disparity and divergence, from the actual volume of water capable of being used on Banchory by the eligible water supply works of at least 8,000ML per annum, of the calculation made by the Department (on which the Decision was based), through the modelling of 3,926 ML per annum and on purported application of the Eligible Works Model, demonstrates both a departure from the required standard of reasonable accuracy and correctness under Division 2 of Part 2A of the Regulation, a breach of the requirement of clause 23I(2)(a) for a determination of the landholder’s eligible water supply work, and in the alternative, a result that is manifestly or legally unreasonable in terms of both the process by which it was reached and in the result arrived at in the Decision.

As a result, the Decision is vitiated by jurisdictional error.

Further, the figure of 3,926 unit shares or 3,926 ML (or the original figure of 4,041 shares or 4,041ML) was not based on any probative evidence capable of establishing that this was the historic usage by eligible water supply works on Banchory.

To the extent that the other two models referred to in clause 23I (the current conditions model and the plan limit compliance scenario limit model) were used to calculate the final share component of 3,926 shares for Banchory they did not avoid the Decision being manifestly unreasonable, as they were applied, if they were applied at all, to a figure produced by the Eligible Works Supply Model that was not a reasonably accurate and correct estimate of the volume of water capable of being used by a Banchory’s eligible water supply works for the water source within the meaning of clause 23I(2)(a) of the Regulation.

In addition to 46B above, the application of the Macquarie hydrologic model on 8 September 2022 to reduce the original share component of 17 June 2022 being 4,041 shares (or 4,041ML) to the 3,926 shares (or 3,926ML) the subject of the Decision was not based on any probative evidence that such a reduction was required in order to comply with the long term average annual extraction limit as defined in clause 23A of the Regulation.

The determination by the Eligible Works Model, for Banchory of an amount of water that was a reasonably accurate and correct estimate of the volume of water capable of being used by a landholder’s eligible water supply works for the water source within the meaning of clause 23I(2)(a) of the Regulation was a matter of jurisdictional fact and a statutory precondition for the Decision.

The relevant jurisdictional fact did not exist for the Decision as the amount calculated by the Defendant was not a reasonably accurate and correct estimate volume of water capable of being used by the Plaintiff’s eligible water supply works at Banchory for the water source, within the meaning of clause 23I(2)(a) of the Regulation.

As a result, the Decision is vitiated by jurisdictional error.

In addition, the Decision was manifestly or legally unreasonable in limiting the entitlement to harvest floodwaters to floodwater from one Management Zone only, Lower Macquarie Upstream Management Zone, when Banchory had historically harvested from both that zone and the Gum Cowal Management Zone.

As a result, the Decision is vitiated by jurisdictional error.

In all the circumstances, the Decision was either invalid or a nullity, not being a determination under Division 2 of Part 2A of the Regulation.

Grounds for leave

Leave should be granted to challenge the Decision beyond the 3 month period in r59.10 in circumstances where the Plaintiff has been seeking to assert a right of merits appeal in the Land and Environment Court (and Court of Appeal) pursuant to s368(1) of the Water Management Act 2000, such right being denied as a matter of law by the Land and Environment Court in the decision of her Honour Pain J in Ramsay v The Minister for Land and Water; Hospitality and Racing, The Minister administering the Water Management Act 2000 [2023] NSWLEC 66 on 26 June 2023.This decision was upheld by the Court of Appeal in [2023] NSWCA 299.

13. These grounds highlight the critical need to understand how the hydrological models work (particularly the eligible works model) and the data inputs they use. As the Court of Appeal explained in Ramsay at [65]:

there [is] nothing discretionary about the specification of the relevant share component: it is a requirement under the WM Act that the licence identifies its share component. This is not something expressed to be “at the Minister's discretion”: cf. ss 63A(1) and 63B(1). The share component is the function of the output of a number of models which the Minister was required to follow.

14. In the substantive proceedings the parties have filed lay and expert evidence, including two joint reports by their respective hydrology experts. The plaintiffs also filed outlines of written submissions.

15. It is necessary to now describe the expert evidence filed in the substantive proceedings.

16. The Ramsays retained Dr Daniel Martens as an expert. The Minister retained Mr Daren Barma as an expert. It appears that rather than each providing his own expert report the Court ordered by consent that the experts prepare a joint expert report. This resulted in the joint expert report dated 17 September 2024 for Banchory and a joint expert report dated 18 September 2024 for Flintrock. Subsequently, on 23 October 2024, Dr Martens and Mr Barma provided a supplementary joint expert report for Banchory and a separate supplementary joint expert report for Flintrock. These are the four reports the subject of the Minister’s notice of motion.

17. The substantive proceedings were listed for hearing before Davies J from 29 October to 31 October 2024. But on 29 October 2024, the three day hearing was vacated by consent on the basis that the parties had reached an in-principle agreement to set aside the determinations.

18. There was then a series of directions hearings during the period 9 December 2024 to August 2025, during which time the parties sought to give effect to the in-principle agreement.

19. During this period, on 16 June 2025, Elkaim AJ published his judgment in Budvalt Pty Ltd v The Minister for Lands and Water; Hospitality and Racing, the Minister for Administering the Water Management Act 2000 [2025] NSWSC 609. His Honour set aside the Minister’s determination of a share component for an FH licence regarding two separate properties within the Water Sharing Plan for the Barwon-Darling Unregulated River Water Source 2012. His Honour held that the Minister’s determinations were vitiated by jurisdictional error. In particular, his Honour found at [112] that cl 23I of the WM Regulations had not been lawfully applied because the model used to determine the share entitlements in that case omitted an important element, which his Honour described as “consideration of direct irrigation to crops”.

20. The Ramsays claim that Budvalt is directly applicable to their case.

21. The Minister appealed that decision but shortly before the appeal was to be heard by the Court of Appeal the proceedings were discontinued by the Minister.

22. In the meantime, in the Land and Environment Court, Preston CJ published his reasons for judgment in another judicial review challenge to separate FH licences in Emu Rider Pty Ltd ATF the trustee for Griffiths Investment Trust v Minister administering the Water Management Act 2000 [2025] NSWLEC 64. This judgment was published on 24 June 2025, approximately one week after publication of Budvalt. In Emu Rider (which was in Class 4 of the Land and Environment Court’s jurisdiction), six landholders in the NSW Border Rivers Water Management Area challenged the validity of the Minister’s decision concerning the issue of replacement FH licences, including on grounds of jurisdictional error. It should be noted that the relevant licences were purportedly issued under the WM Act and Water Management (General) Amendment Regulation 2021 (NSW) (2021 Regulations) (as opposed to the WM Regulations which is relevant to the present proceedings).

23. The judicial review challenge in Emu Rider was successful on some but not all of the pleaded judicial review grounds. In particular, Preston CJ rejected the applicants’ contentions that the FH licences were invalid on the basis that the models which were used there were non-compliant with s 57A of the WM Act and cll 23G-23J of the 2021 Regulations. The Chief Judge rejected the applicants’ claims that:

(a) the models did not take into account rainfall run-off and overtopping, two forms of overland flow water flowing over the floodplain; (b) the models were not capable of converting the actual or proposed floodplain water usage of each eligible landholder into a share component of an FH licence; (c) the models were not capable of representing the estimated volume of water used by each landholders’ eligible water supply work for the water; and (d) the models were not capable of being used to ensure that any adjustment required to ensure the long-term average annual extraction limit, or the floodplain harvesting part of the limit, is not exceeded, and is proportionally allocated to each landholder who has an eligible water supply work for the water source by way of the share components of the FH licences.

24. In brief, in respect of these unsuccessful grounds of judicial review, Preston CJ at [224] found that cl 23G(1) of the 2021 Regulations allowed the Minister “an area of decisional freedom to assess the adequacy of the three models referred to in cl 23G(1)”. With particular reference to the challenge to the adequacy of the models regarding rainfall run-off and overtopping, Preston CJ said at [227]:

…The models did deal with such overland flow water, although indirectly at the valley-scale rather than directly at the farm-scale. That indirect consideration of overland flow water did not cause the models not to be models within the description or for the purposes of cl 23H, cl 23I or cl 23J of the 2021 Regulation. Reasonable minds may differ as to how overland flow water ought to be taken into account by the models. The Minister’s delegate’s decision to adopt the models which indirectly dealt with overland flow water was within the decisional freedom afforded by cl 23G(1) of the 2021 Regulation. The models could not be said to be so inadequate and unreliable as to be of no use whatsoever in determining the share components of replacement floodplain harvesting access licence: see Arnold v Minister Administering the Water Management Act 2000 [2014] NSWCA 386 at [107].

25. In the substantive proceedings here, the Minister contends that [64] and [65] of Emu Rider support her position. In contrast the Ramsays say the reasoning there is limited to the current conditions model and does not extend to the eligible works model.

26. Returning to the chronology of the present proceedings, on 17 April 2026, the Minister sent an open offer to the Ramsays offering to resolve the proceedings by setting aside the impugned determinations on the basis of jurisdictional error, to pay the Ramsays’ costs and redetermine the share components.

27. The conceded jurisdictional error related to an error in the inputs into the plan limit compliance scenario model which the Minister acknowledged amounted to a failure to use that particular model in the manner required by cl 23C(2) of the WM Regulations. The Minister acknowledged a mistake in the coding of the modelling used in the making of the impugned determinations.

28. In the letter dated 17 April 2026, the Minister’s solicitor said that the error occurred in the context of applying an aspect of the accounting rules and, in particular, the rainfall run-off harvesting exemption in calculating the proposed share component, which is inputted into the plan limit compliance scenario model (as referred to in cl 23J(1)(a) of the WM Regulations). Reference was made to the description of the modelling exercise on page 6 of a September 2022 Report entitled “Floodplain harvesting entitlements for the Macquarie Valley regulated river system: Model Scenarios”. The letter further explained that the plan limit compliance scenario model was developed with the aid of a “Python Code” which was applied to the outputs of the eligible water supply work scenario model. This Code contained “a Boolean error which reversed the criteria for applying the exemption status to developed area run-off which impacted the exempt and non-exempt rainfall run-off diversions figures of Flintlock and Banchory”.

29. The letter further explained that use of corrected figures for exempt rainfall-run-off diversions concerning Banchory and Flintrock would result in an increase to each share component for those properties, but that the increase would be “materially less than the amount proposed in each Amended Summons”.

30. The open offer was rejected by the Ramsays. This is one of the unusual features of the case. Under the Minister’s offer the determinations would have been set aside and the matters reconsidered. If the Ramsays succeed in their judicial review challenges the relief would presumably be much the same.

31. It is necessary to now say something more regarding the supplementary joint expert reports. In October 2024 (i.e. shortly before the scheduled 3 day hearing at the end of the month), the Department became concerned about deficiencies in the earlier joint expert reports. To address those deficiencies, the Department forwarded to the Ramsays’ solicitor a proposed statement of agreed facts and a series of issues to be put to the joint experts so that they could produce supplementary joint expert reports which would explain at greater depth the basis for the conclusions in the original joint expert reports.

32. The proposed statement of agreed facts was accepted but the Ramsays’ solicitor did not agree with all the proposed issues being put to the experts, pointing to the then imminent hearing of the substantive proceedings. He agreed that only the following two questions be put to the experts:

Question 1 – What is the basis of your opinions contained in the original JER? Please set out the reasoning, facts and assumptions on which each opinion, per issue is based.

Question 2 – What are the calculations you used to arrive at the agreed total in Issue 7 in the JER? This will need to be contained in spreadsheets for each expert which are to be annexed to the supplementary JER.

33. As noted above, on 23 October 2024, supplementary joint expert reports were provided in both the Banchory and Flintrock proceedings. These supplementary joint expert reports, together with the original joint expert reports, are the subject of the Minister’s notice of motion. The Minister claims that these reports are inadmissible and that further expert hydrology evidence and lay evidence from the Department’s modellers is necessary to determine the issues in the substantive proceedings. Otherwise, the Minister says that there will be no lay or expert evidence explaining the alleged errors or operation of the models which are at the heart of the proceedings.

Disposition

(a) The appropriateness of giving an advance ruling here

34. Section 192A of the Evidence Act provides that:

Where a question arises in any proceedings, being a question about—

(a) the admissibility or use of evidence proposed to be adduced, or

(b) the operation of a provision of this Act or another law in relation to evidence proposed to be adduced, or

(c) the giving of leave, permission or direction under section 192,

the court may, if it considers it to be appropriate to do so, give a ruling or make a finding in relation to the question before the evidence is adduced in the proceedings.

35. Section 192A confers a broad discretion on the court to give a ruling or make a finding in relation to evidence prior to that evidence being adduced in the proceedings. The section specifies only one test for the exercise of the discretion to give an advance ruling, namely that the Court “considers it appropriate to do so”. A general consideration which will support the making of an advance ruling by the court will include serving the interests of justice by enhancing the overall efficiency of the trial.

36. A good reason should be advanced by the party seeking that the Court exercise its jurisdiction under s 192A, however, it is not necessary to show “special circumstances” or to demonstrate that the circumstances are “out of the ordinary” (Beslic v MLC Ltd [2015] NSWSC 908 at [33] per Robb J adopting the principles stated by Stevenson J in Lambert Leasing Inc v QBE Insurance Australia Ltd [2012] NSWSC 953 at [11]-[13]).

37. In Searle v Commonwealth (No 5) [2022] NSWSC 119 at [39], Garling J set out some of the relevant principles as to how the Court should determine whether or not to exercise its power under s 192A (quoting from A**ustralian S**ecurities and I**nvestments C**ommission, Re Whitebox Trading Pty Ltd v Whitebox Trading Pty Ltd [2017] FCA 324 at [21]ff per Gleeson J):

Section 192A permits but, does not compel, advance rulings to be given on the admissibility of evidence: Bailey v Director-General, Dept of Natural Resources [2013] NSWSC 515 at [55]. Whether the Court should make an advance ruling is a ‘discretionary case management decision’: NA & J Investments Pty Ltd v Minister Administering Water Management Act 2000 (No 4) [2012] NSWLEC 120 AT [40]; Beslic v MLC Ltd [2015] NSWSC 908 at [33].

The authorities indicate that ‘some good reason should be advanced in order that the court exercise jurisdiction under s 192A’: … It may, for example, be appropriate to give an advance ruling ‘if all matters relevant to the issue have been or can then be ascertained and if it is clear that a ruling will inevitably be required’: TKWJ v R [2002] HCA 46; (2002) 212 CLR 124 at [42] (Gaudron J). Further, the giving of a ruling, or the making of a finding, under s 192A may be appropriate where ‘a considerable amount of time, effort and money might be saved if the documents were ruled to be admissible now’.

A sound reason to refuse to give a ruling under s 192A may exist where the proceeding is in its infancy, the issues have not yet been joined because the pleadings have not closed and it is uncertain whether the evidence sought to be the subject of the advance ruling will be relied upon at final hearing.

38. A survey of some of the relevant cases by Rees J in Owners – Strata Plan No 90189 v Parkview Constructions Pty Ltd [2022] NSWSC 1382 at [42] indicates that it may be appropriate for the Court to give an advance ruling in the following kinds of circumstances (which are not exhaustive):

(a) Where it is clear that there are issues or “serious questions” regarding the admissibility of the evidence in question: Sydney Attractions Group Pty Ltd v Schulman [2012] NSWSC 951 at [27], [31] (Stevenson J). Thus in NA & J Investments Pty Ltd v Minister Administering the Water Management Act 2000 (No 4) [2012] NSWLEC 120, Biscoe J at [45] was prepared to make an advance ruling on lay evidence in circumstances where the admissibility of that evidence was “in sufficient doubt to justify the making of advanced rulings”, and where the advance ruling would promote the efficiency of the conduct of the trial by saving time and cost as the lay witnesses would no longer be required for cross-examination. (b) It is inevitable that a ruling will have to be made in respect of that evidence, such that the Court’s time will not be wasted in doing so: Southern Cross Airports v Chief Commissioner of State Revenue [2011] NSWSC 349 at [15] (Gzell J). (c) The material necessary to make an advance ruling has been or can be ascertained: TKWJ v The Queen (2002) 212 CLR 124; [2002] HCA 46 at [42] (Gaudron J). (d) Such a ruling will assist with the efficient conduct of the final hearing, including by giving the party whose evidence is the subject of an adverse advance ruling the opportunity to marshal evidence in proper form, avoiding the need to call witnesses or to require other witnesses for cross-examination, or where there is an objection to the trial judge considering the evidentiary material: Coastal Service Centres Pty Ltd v United Petroleum Pty Ltd [2020] NSWSC 1870 at [53] (Ward CJ in Eq). (e) “Section 192A, in an appropriate case, might permit the party to serve evidence prepared in the simpler and less expensive way, and then to seek a ruling under s 192A, in advance of the hearing, on the admissibility of the evidence. The very purpose might be to give the party an opportunity to serve further evidence prepared in the more complicated and expensive way, if necessary to do so”: Beslic v MLC Ltd [2015] NSWSC 908 at [35] (Robb J).

39. On the other hand, the following cases identify the kinds of circumstances where it may be inappropriate for the Court to exercise its discretion to give an advance ruling (which are not exhaustive):

(a) Where the objection to the admissibility of the evidence is on the ground of relevance. The Court may refuse to make an advance ruling where it cannot ascertain whether the evidence is irrelevant and therefore inadmissible, as the true position as to the relevance of the evidence may be nuanced and an advance ruling may result in an error and consequent unfairness; the relevance of the evidence may “depend on the way the case unfolds at trial”: Gondarra v Minister for Families, Housing, Community Services and Indigenous Affairs (2012) 127 ALD 288; [2012] FCA 185 at [23]-[29] and [41] (Kenny J). (b) A related consideration is whether there is a risk that assumptions which are made about evidence to be adduced in a case prove ultimately not to be correct in light of the way in which a case is in fact presented: Bailey v Director-General, Department of Natural Resources [2013] NSWSC 515 at [56] (Garling J). (c) Where not all the pleadings have been filed or not all of the evidence has been served, such that the issues to be tried are not fully exposed or completely defined or it is uncertain whether the evidence sought to be the subject of the advance ruling will be relied upon at final hearing: Trusted Cloud Pty Ltd v Core Desktop Pty Ltd [2015] FCA 33 at [56]-[57], [60]-[61] (Katzmann J); Australian Securities and Investments Commission, in the matter of Whitebox Trading Pty Ltd v Whitebox Trading Pty Ltd [2017] FCA 324 at [24] (Gleeson J). (d) In Wadsworth v Hamilton [2022] NSWSC 396 at [32]-[52], N Adams J refused to make an advance ruling under s 192A in relation to an expert report filed by the plaintiff in circumstances where the matter was not listed for a trial date, had not been allocated a judge for the final hearing, and where the defendant had not yet filed its expert evidence. Relevantly, her Honour said that the making of the application well in advance of a hearing was a “discretionary factor weighing against any advance ruling being made” (at [51]).

40. With those general guiding principles in mind, I shall now explain why I consider it is appropriate to give advance rulings as sought by the Minister.

41. First, whether the joint expert reports are admissible will critically inform how the proceedings run from this point. It will inform whether further written or oral expert evidence is required. That can be efficiently determined now, and need not be determined on the first day of trial when it is too late to fix. I do not accept the Ramsays’ contention that there are no “obvious evidential” problems with the joint expert reports.

42. Secondly, it appears that there is some potential to reconstruct the models used by the Department by reference to two lengthy reports, namely, the Building the River System Model for the Macquarie Valley Regulated System, Conceptualisation, Construction and Calibration (April 2023) (the Model Build Report) and the Floodplain Harvesting Entitlements for the Macquarie Valley Regulated River System Model Scenarios (September 2022) (the Scenarios Report). It would be necessary, however, to have the expert witnesses elaborate upon those reports at the hearing. I accept the Minister’s submission that this could be a lengthy process and is likely to take up substantially more court time, particularly having regard to the complexity of the modelling process and the current lack of guidance in the evidence provided to date. The essential need for admissible expert evidence is reinforced by the inherent complexity of the regulatory framework within which the determinations were made.

43. Thirdly, I understand that these proceedings are likely to have implications for other landowners and for the modelling of share entitlements generally. It is appropriate, therefore, to seek to resolve the admissibility of the reports at this stage and provide an opportunity for the judicial review issues to be heard and determined with reference to admissible evidence.

44. Fourthly, preparation for the hearing has well progressed and there is little doubt that the plaintiffs will seek to rely upon the joint expert reports. Accordingly, there is no risk that an advance hearing on admissibility is only of peripheral importance. I note that the Ramsays have acknowledged in their outline of written submissions that, although they oppose the Court giving an advance ruling, they appreciate that a preliminary ruling “could well be an efficient course” if there are evidential problems with the expert evidence.

45. Fifthly, the focus of the Ramsays’ judicial review claims has been clarified by their provision only recently (21 and 26 May 2026) of particulars of the amended summonses.

46. Sixthly, as noted above, the judgment in Budvalt is likely to figure prominently in the proceeding and it is desirable that its relevance be assessed by reference to admissible evidence.

47. Finally, as noted above, assuming that the determinations are set aside, they will need to be remitted for redetermination. It is plainly desirable that that process occur with reference to relevant admissible evidence in the present proceedings.

(b) The admissibility of the four joint expert reports

48. Section 79(1) of the Evidence Act provides an exception to the general rule that evidence of an opinion is not admissible:

(1) If a person has specialised knowledge based on the person’s training, study or experience, the opinion rule does not apply to evidence of an opinion of that person that is wholly or substantially based on that knowledge.

49. The requirement in s 79(1) that the expert’s opinion be based “wholly or substantially” on their specialised knowledge means that the reasoning process leading to the formation of the opinion must be made clear.

50. In Menz v Wagga Wagga Show Society Inc (2020) 103 NSWLR 103; [2020] NSWCA 65 at [108] Leeming JA (with whom Payne and White JJA agreed) said that:

In order to comply with s 79, an expert’s opinion should expose his or her reasoning in a way that shows that it is based on particular specialised knowledge: Rolleston v Insurance Australia Ltd [2017] 19 ANZ Insurance Cases 62‐142; [2017] NSWCA 168 at [6] and [32]. The requirement that an opinion be based on specialised knowledge is normally satisfied by the person who expresses the opinion demonstrating the reasoning process by which the opinion was reached: Roads and Maritime Services v Grant (2015) 70 MVR 520; [2015] NSWCA 138 at [131].

To similar effect, see Ocean Marine Mutual Insurance Association (Europe) OV v Jetopay Pty Ltd (2000) 120 FCR 146; [2000] FCA 1463 at [23] per Black CJ, Cooper and Emmett JJ and Herron v HarperCollins Publishers Australia Pty Ltd (2022) 292 FCR 336; [2022] FCAFC 68 at [503] per Lee J.

51. A failure to articulate or expose the process of reasoning that underpins an expert opinion may also bear upon the question of relevance under s 56 of the Evidence Act because it may not be possible to assess whether the expert opinion is capable of rationally affecting the probabilities of the existence of a fact in issue (see e.g. Sydneywide Distributors Pty Ltd v Red Bull Australia Pty Ltd (2002) 234 FCR 549; [2002] FCAFC 157 at [14] per Branson J).

52. The expert should distinguish between all the factual assumptions underlying their opinion and the opinion itself. As Mansfield J explained in Risk v Northern Territory [2006] FCA 404 at [469] (emphasis added):

The important thing in any expert's report, in my view, is that the intellectual processes of the expert can be readily exposed. That involves identifying in a transparent way what are the primary facts assumed or understood. It also involves making the process of reasoning transparent, and where there are premises upon which the reasoning depends, identifying them.

53. His Honour went on to qualify this statement at [472]-[473]:

Branson J said in [Quick v Stoland Pty Ltd (1998) 87 FCR 371] at 375 that “[T]he distinction between evidence of ‘fact’ and evidence of ‘opinion’ assumes a dichotomy which is not always easy to draw”.

In my view, whilst the clear separation of fact and premise from opinion is clearly desirable, it is necessary to accept that there is sometimes difficulty in discerning between the facts upon which an opinion is based and the opinion itself … Such a difficulty should not be regarded as a fatal flaw that may render the report or the opinion inadmissible…. [although it] should not excuse the expert from appreciating the need for transparency in the report and in oral evidence on the matter explained so far as that is possible, so that time and effort is not inappropriately wasted on trying to identify from a poorly constructed report the facts or premises underlying the opinions expressed in it, and the points at which an interpretive or judgmental opinion has been formed and the reasons for it.

54. Applying those general principles here, I shall now explain why I regard the four expert reports to be inadmissible.

55. First, the experts have not adequately explained the basis for many of their opinions. Whilst there is a generalised reference to the sources on which the data is based, the inputs to each model are not adequately explained. Nor are the lengthy and detailed spreadsheets which are attached to the supplementary reports.

56. Secondly**,** the experts have not adequately exposed their reasoning for any of their evaluative or modelling conclusions. The Court is left in the position where it is unable to discern whether the experts’ conclusions are based on their specialised knowledge.

57. Thirdly, I accept the Minister’s submission that the joint expert reports use technical language which is not always explained and which does not correlate with the language used in the WM Regulations, the Model Build Report or the Scenarios Report. This makes it impossible to understand the reasoning. Examples include “set up scenarios”, “flood plain harvesting (FPH) take rules”, “constrained use” and “modelled diversions”.

58. In their outline of written submissions, the Ramsays describe [37] and Table 3 in the initial reports as “a key paragraph as it outlines that on an application of the eligible works model to the assumed historical works assumed by the Department in this case, the share entitlement arrived at should have been 2,709 unit shares” (in the case of Flintrock). The difficulty with this paragraph (and with the equivalent paragraph concerning Banchory) is the absence of any sufficient explanation as to how the share component figures were arrived at.

59. This difficulty is exacerbated by the spreadsheets which are annexed to both the supplementary joint expert reports. The spreadsheets indicate that the eligible works model does not produce a single number. Taking the Banchory spreadsheets as an example, there are four “worksheets” in a single excel document. The third worksheet is in a tab entitled “EW_M031_Data” and the worksheet itself has the title “Eligible Works Model for Banchory (M031)”. That worksheet shows in the left-hand table that the direct outputs of that model are three daily outputs over a period from 1 January 1889 (row 4) to 30 July 2021 (row 48,426) being for each of “On Alloc Diversion (ML)”, “OFH Dev ML” and “OFH Not Dev ML”. The right-hand table shows each of these outputs on an annualised basis. These are the outputs from the eligible works model. Importantly, it is not a single number of [X] ML per year, as [37] of the initial joint expert reports suggests.

60. The fourth worksheet is in a tab entitled “EW_M031_FPHCalc” and the worksheet itself has the title “Application of Water Accounting Rules”. It is clear enough that this worksheet takes the outputs from the eligible works model and applies further calculations to them to give effect to the water accounting rules. However, there is no explanation in this worksheet of how the calculation was conducted. The figure of 4,206 is not solely an output of the eligible works model as the accounting rules have been applied. As the Minister contends, the most logical explanation is that these calculations are a product of some other unexplained process which manipulates the outputs of the eligible works model.

61. I do not consider that these problems are overcome by the experts’ attempt at [11] of the supplementary joint expert reports to explain the basis for the conclusion at [37]. This further explanation suggests little more than the figures set out in Table 3 were not an output from merely using the eligible works model.

62. Another failure properly to explain opinions held by the experts is evident in [33] of each of the original reports. It is declared there that the third model (the plan limit compliance scenario model) was not used in making the determinations, yet no reasoning is provided for that assertion. It also appears to contradict the description of “step 7” at [22] of the reports. And at [43] of the joint expert reports, it is suggested that the plan limit compliance scenario model was in fact applied. These contradictions and inconsistencies are simply left unexplained, generating considerable confusion and uncertainty.

63. As the Minister also points out, tabs 8 and 9 of the Floodplain Harvesting Entitlements Report disclose that the plan limit compliance scenario model was used. However, early in each of the initial joint expert reports, in the context of purporting to describe the various steps in the modelling process, the experts describe step 7 at [22] as involving:

add[ing] the entitlements and proposed accounting rules from the utility program to the CC model to create (a new scenario) the Plan Limit Compliance Model. This scenario is used to demonstrate modelled diversions comply with the Plan Limit, which is set for the valley.

64. The patent deficiencies in the initial joint reports are not overcome in the supplementary joint reports. One example relates to issue 1 (Water Sources). The experts were asked to address whether the Department’s modelling incorporated all floodwater intercepted by the Ramsays’ eligible water supply works. In the initial joint expert reports at [25], the experts responded by setting out Table 1 which contained different figures in relation to the current conditions model and the eligible works model. How those different figures are arrived at is simply left unexplained. The supplementary joint report takes the matter no further even though the experts were instructed to state the basis of their opinions in the original report and set out the reasoning, facts and assumptions upon which each opinion was based. The reasoning given in relation to issue 1 (Water Sources) is simply as follows:

Reasoning

• The documented maximum [crop] irrigation areas, undeveloped areas, and associated infrastructure parameters including storage and FPH pump capacity were data extracted from the IQQM Macquarie River System Model, for both the CC Model and Eligible Works Model.

• The Department’s modelling incorporated flood water intercepted by the Plaintiff’s eligible water supply works where this was directed to an eligible storage and the eligible storage was not already full. Flood waters pumped by the Plaintiff from a floodplain directly into a cropped area or an area other than a storage were not incorporated into the Department’s modelling.

As the Minister correctly pointed out, the experts made no attempt to explain why the Department’s modelling did not incorporate floodwaters directly pumped to a cropped area or non-storage area. Yet this issue is at the heart of the Ramsays’ case, with the strong reliance they place on Budvalt.

65. This “reasoning” is not admissible. Not only does it fail to identify the assumptions on which these conclusions are based but it does not identify the reasons that the experts say the floodwaters were “not incorporated in the Department's modelling”. The Court cannot tell from this evidence whether the sentences are an assumption or a conclusion and, if the latter, whether it is based on the expert’s expertise or some other inference. But a significant issue in the proceedings is how the models deal with what is described as “direct irrigation”, i.e. water used for irrigation from floodplain harvesting directly, without being drawn from a water storage area.

66. These significant difficulties are sufficient of themselves to have the joint expert reports excluded from the evidence.

67. I also accept the Minister’s submission that there are additional problems which include the following.

68. First, the experts have not attempted to identify how the models are understood to operate. Each initial report refers to the current conditions model (at [14(a)]). It is said to be based on irrigation infrastructure, water licences and water management regimes at the Determination Date and uses data from a range of sources (at [14(a)(ii)]). But neither report explains what the model does.

69. Each report also refers to the eligible works model (at [14(b)]). Again, they state that it is based on irrigation infrastructure, water licence and water management regimes (as at 3 July 2008) and uses data from a “similar range of sources to that used for the CC Model”. This does not identify what the model is or how it should work. Indeed, because the models are described in almost identical terms, the reader is left to wonder: what is the difference between them? What do they do? Is the description of each model an assumption or an evaluation based on the witnesses’ expertise? I accept the Minister’s submission that none of these questions can be answered from the expert reports.

70. Secondly, the answers to issue 2 (whether any water sources or management zones artificially constrained the modelling) in the joint expert reports is incomprehensible and is not clarified in the supplementary reports. The experts are content simply to assert that relevant water sources and management zones were included in the Department’s modelling, without explication.

71. Thirdly**,** as to issue 3 (to what extent the Department’s modelling met the descriptions of the “current conditions model”, the “eligible water supply works scenario model” and the “plan limit compliance scenario model”), a table is supplied without any proper explanation of the meaning of the data (at [32]). I accept the Minister’s submission that it is impossible to evaluate what the figures mean or whether they reflect assumptions or evaluations based on expertise.

72. Fourthly, as to issues 4 and 5 (about the extent to which the Department misapplied the current conditions model and the eligible works model), there is no reasoning given. The ultimate answer in each joint expert report is that the share component should be different (see at [46]). The high point of the experts’ explanation is that the “extent to which the Department applied or misapplied the model is inferred in the differences in the FPH entitlements in Table 3 and those issued” (supplementary joint expert report at [11]). No reasoning is provided which exposes the path used by the experts to arrive at that conclusion.

73. Fifthly, as to the ultimate answer to issue 7 (the extent to which the material supported a different share entitlement), the Banchory report says the share component should be 4,206 unit shares (at [46]). The entire reasoning is:

By reference to the response to Issues 4 and 5, on the basis of the assumptions made in respect [of] on-farm pump, storage, cropped and undeveloped area details contained in the Eligible Works Model, the modelling supported a Licence share component of around 4,206 unit shares.

74. The conclusion is identical in the Flintrock report except the number is “2,709 unit shares” (at [46]). The conclusions are not responsive to the question which the experts were asked to address. Moreover, how the experts arrived at different figures to those posed in the question is left unclear.

75. I accept the Minister’s submission that the reference in the reasoning to “the results of Issues 4 and 5 in respect of the Eligible Works Model” is a reference to inadmissible expert evidence. It refers to various “assumptions” without attempting to identify what those assumptions are. There is no explanation for why the experts have reached a different share component outcome for both Banchory and Flintrock to those in the determinations. It is impossible to evaluate the extent to which the answer is based on the experts’ expertise.

76. These problems are not overcome by the supplementary reports. The experts were asked by question 2 to identify the calculations used (reflecting the reality that no calculations were identified in the initial reports). The entire answer was:

Spreadsheets used to derive the agreed total in Issue 7 are annexed in electronic form to this supplementary report.

77. The reader of the reports is effectively left to discern how the spreadsheets were used. The spreadsheets, which occupy hundreds of pages, were prepared by the experts. As the Minister contended, however, the share component figures which appear in the spreadsheets leave uncertain how the figures were reached and whether the experts’ processes are the same as those used by the Department. The experts provide no explanation or assistance at all in understanding the spreadsheets.

78. Moreover, as the Minister also pointed out, the parameters for the data inputs in the spreadsheets are inconsistent and not explained. For example, taking the Banchory spreadsheets as an example, the worksheet entitled “EW_M031 _Data” has a data period commencing on 1 January 1889 (row 4) and ending on 30 July 2021 (row 48,428) yet the next worksheet entitled “EW_M03 1_FPHCalc” has a different data period ranging from 30 June 1890 (row 5) to 30 June 2014 (row 129). The experts provide no reason for this discrepancy or their choice of data periods. It is evidently not the same period as the Department used, which was identified at p.98 of the Model Build Report as being “01/07/1895 to 30/06/2009”**. There is no explanation for these choices which means that the basis for the experts’ ultimate opinion (as to the appropriate share component determination) cannot be understood.

79. The problems and difficulties created by large parts of the joint expert reports are sufficiently grave to render the reports inadmissible as a whole and I rule accordingly.

(c) Further case management

80. On one view, it is not easy to see how the Ramsays can discharge their onus with all four expert reports being inadmissible. I do not accept their submission that even if parts of the reports are inadmissible other admissible parts of the reports provide a sufficient evidentiary basis for the claimed reviewable errors. As I have explained above, the nature and scope of the evidentiary problems are of such a magnitude that it is not possible to salvage other parts of the reports. The reports are too self-contained for that to occur.

81. As noted above, the Minister has emphasised the test case character of the proceedings and the likely ramifications for parts of the State where floodplain harvesting is regulated using the three models referred to in cl 23G(1) of the WM Regulations. I accept the Minister’s contention that it is important that the Court have the benefit of a correct factual description of how the models operate, including relevant expert evidence going to the issues raised in the judicial review proceedings.

82. I do not accept the Ramsays’ submission that, if the Court ruled the reports inadmissible, the experts should participate in another conclave and produce another joint report. I have no confidence that this would be a meaningful process having regard to the history of the matter.

83. In all these circumstances, leave should be granted to the Minister to file and serve an affidavit by 19 June 2026 by Andrew Brown, a departmental officer whom I understand will provide lay evidence explaining in detail what the data inputs are.

84. Leave should also be granted to the Minister to adduce a lay affidavit by an officer of the Department or the Regulator by 19 June 2026, should the Minister decide to do so.

85. The parties should have an opportunity to adduce fresh expert evidence in an admissible form. As the Ramsays carry the onus of proof, they should attend to this matter first. Accordingly, I grant leave to the Ramsays to adduce additional lay and expert evidence by 31 July 2026.

86. Leave should also be granted to the Minister to file and serve an expert report in response by Mr Barma by 11 September 2026. I consider that the experts (not including Mr Brown) should then confer and produce a joint expert report by 2 October 2026 which identifies the points of agreement and disagreement and provides a sufficient explanation of the same.

87. The parties have liberty to apply on the giving of 48 hours’ notice.

88. Finally, costs of the Minister’s motion in both proceedings should be costs in the cause.

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