Although monitoring is crucial for environmental science and policy, few studies have assessed its value for the public. To value the public preferences for environmental monitoring related to hydropower, we designed a discrete choice experiment, used the Q-methodology to select attributes and assessed preferences for monitoring with a split-sample design. While both samples faced decisions about hydropower management, one sample was informed that an environmental measure's efficacy was unknown due to a lack of monitoring. We found that uncertainty significantly reduced utility levels and willingness to pay, which indicates that the public positively values monitoring. By accounting for heterogeneous preferences using both the mixed logit and latent class approach, our results were confirmed irrespective of the socio-demographic profile. In our application to environmental hydropower, we find strong support for fish protection and opposition to foreign ownership. In light of the growing number of environmental policies (e.g., Water Framework Directive) that mandate monitoring, these findings highlight the need to account for its positive externalities. Thus, we recommend that decision makers include the public value of monitoring in environmental cost-benefit analyses.

尽管监测对于环境科学和政策至关重要，但很少有研究评估其对公众的价值。为了评估公众对水电相关环境监测的偏好，我们设计了一个离散选择实验，使用 Q 方法选择属性，并通过拆分样本设计评估监测偏好。虽然两个样本都面临有关水电管理的决定，但一个样本被告知由于缺乏监测，环境措施的功效未知。我们发现不确定性显着降低了效用水平和支付意愿，这表明公众积极重视监测。通过使用混合 logit 和潜在类别方法来考虑异质偏好，我们的结果得到了证实，而不管社会人口特征如何。在我们对环境水电的应用中，我们发现对鱼类保护和反对外国所有权的强烈支持。鉴于要求监测的环境政策（例如，水框架指令）越来越多，这些发现强调需要考虑其积极的外部性。因此，我们建议决策者将监测的公共价值纳入环境成本效益分析。