Globally, the agriculture sector is the largest user of groundwater, and to manage declining groundwater resources, reducing groundwater extraction by the agriculture sector is an active policy objective in many jurisdictions. Estimating the cost to agriculture in terms of lost gross margin due to the implementation of exogenously determined water extraction restrictions has been an active research area. This research contributes to the literature on groundwater management by developing a hydro-economic farm optimization model that allows us to internalize the environmental externalities associated with groundwater extraction and compare outcomes with various levels of uniform proportional cuts to agricultural groundwater extraction rights. Our case studies are three sub-areas within Western Australia’s most important groundwater system: the Gnangara Groundwater System. We find evidence that: (i) once environmental externalities are accounted for, the optimal water use by horticulture falls by between 26% and 38% across the three sub-areas; and (ii) compared to a uniform proportional cut policy, spatially and temporally flexible policy mechanisms achieve higher environmental gain with a lower cost to horticulture.

在全球范围内，农业部门是最大的地下水使用者，要应对不断减少的地下水资源，减少农业部门对地下水的开采是许多辖区的一项积极政策目标。根据因实施外部确定的水提取限制而造成的毛利润损失来估算农业成本一直是一个活跃的研究领域。这项研究通过开发一种水力经济农场优化模型，为地下水管理提供了文献资料，该模型使我们能够内部化与地下水开采相关的环境外部性，并比较各种水平的统一比例削减对农业地下水开采权的影响。我们的案例研究是西澳大利亚州最重要的地下水系统中的三个子区域：加纳加拉地下水系统。我们发现证据：（i）一旦考虑到环境外部性，园艺在三个分区中的最佳用水量就下降了26％至38％；（ii）与统一的比例削减政策相比，时空灵活的政策机制可实现更高的环境收益，并降低园艺成本。