A crucial decision in defining the scope of an environmental impact assessment is to delineate the initial assessment area. We developed a probabilistic methodology to determine this area, which starts by identifying a key environmental variable, maximum acceptable change and acceptable probability of exceeding that threshold.

The exceedance probability is determined with a limits of acceptability rejection sampling of informed prior parameter distributions. A qualitative uncertainty analysis, a formal and systematic discussion of the main assumptions and model choices, is complemented with global sensitivity analysis of the model results to identify the major sources of uncertainty and provide guidance for further research and data collection.

For the case study on coal development in the Gloucester Basin (NSW, Australia), the initial assessment extent is unlikely to extend more than 5 km from the edge of the planned coal mines. The major source of uncertainty is the planned mine water production rate.

定义环境影响评估范围的关键决定是划定初始评估区域。我们开发了一种概率方法来确定该区域，首先确定关键的环境变量，最大可接受的变化以及超过该阈值的可接受概率。

超出概率是根据已知先验参数分布的可接受性拒绝采样的极限确定的。定性不确定性分析是对主要假设和模型选择的正式和系统的讨论，另外还对模型结果进行了全局敏感性分析，以识别不确定性的主要来源，并为进一步的研究和数据收集提供指导。

对于格洛斯特盆地（澳大利亚新南威尔士州）煤炭开发的案例研究，初步评估的范围不太可能延伸到计划煤矿边缘的5公里以上。不确定性的主要来源是计划的矿井水生产率。