Arnold v Minister Administering the Water Management Act 2000

This case concerned a judicial review application brought by the appellants against the Minister administering the *Water Management Act 2000* (NSW). The dispute centred on the validity of a water sharing plan that reduced water extraction entitlements. The appellants contended that the plan was invalid due to the Minister's alleged failure to comply with mandatory requirements of the Act, including the proper consideration of groundwater recharge and sustainable yield, and that the decision was manifestly unreasonable. The matter was heard on appeal by Meagher and Barrett JJA, and Tobias AJA.

The primary legal issues before the court were whether the Minister was statutorily obliged to use a sound and reliable numerical groundwater model to determine groundwater recharge and sustainable yield, and whether the failure to do so, or the use of a flawed model, rendered the water sharing plan invalid. Further, the court considered whether misleading information provided to the Minister invalidated the decision, and whether the obligation to consider the socio-economic impacts of proposals required a formal socio-economic study.

The court affirmed the primary judge's finding that while the Minister was obliged to consider the water management principles under section 9(1) and section 5(2)(g) of the Act, this did not impose a duty to achieve specific outcomes or to use a particular type of groundwater model. The language of "take all reasonable steps" and "Generally" indicated a less stringent obligation. The court rejected the appellants' submission that the use of a "sound and reliable" groundwater model or the identification of a "true and correct recharge" constituted a jurisdictional fact. Instead, the court viewed this as an argument that the Minister failed to take into account a mandatory relevant consideration, which required an assessment of whether the Act's subject matter, scope, and purpose implied such a consideration. The court found that the Minister had, in fact, considered sustainable yield and recharge, and was not bound to adopt any specific methodology or achieve a particular result.

The appeal was dismissed with costs.