The Japanese environmental flow (e-flow) concept and framework are outlined in the current study. We first review the natural and historical background related to the establishment and implementation of the e-flow framework in Japan. We then summarize the national guidelines used to assess e-flows. Finally, we discuss a river for which the guidelines have been applied to set e-flow requirements. It is legally mandated that flows be established to maintain the riverine environments of class A rivers managed by the national government. These correspond to e-flows, which are referred to as maintenance flows in Japan. A Guideline established in 1997 provides detailed instructions on how to assess e-flows, and the e-flow framework has been implemented for 100 class A rivers according to the guidelines. E-flow objectives in Japan are intended to benefit ecosystems through the protection of river habitats and fisheries and the protection and maintenance of water quality, groundwater levels, riverine scenery, and navigable waterways. E-flow objectives also address cultural and social needs, such as the prevention of salt damage and estuary clogging, and the protection of wooden infrastructure management facilities. Although Japanese rivers are characterized by large fluctuations and sudden peaks in flow, there has been little discussion about e-flow evaluation methods that take flow variability into consideration. This is because dams on Japanese river basins control only a small percentage of total runoff volume. This is one reason why the guidelines for setting e-flows focus only on the minimum flows required to prevent extreme low-flow conditions.

中文翻译：

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环境流量实施的立法框架：日本30年的运作

本研究概述了日本的环境流（e-flow）概念和框架。我们首先回顾了与日本建立和实施 e-flow 框架相关的自然和历史背景。然后我们总结了用于评估电子流的国家指南。最后，我们讨论了一条河流，该准则已应用于设置 e-flow 要求。为维护国家政府管理的A类河流的河道环境，法律规定建立河流。这些对应于电子流，在日本被称为维护流。1997 年制定的指南提供了如何评估 e-flows 的详细说明，e-flow 框架已根据该指南对 100 条 A 级河流实施。日本的 E-flow 目标旨在通过保护河流栖息地和渔业以及保护和维护水质、地下水位、河流景观和通航水道来造福生态系统。E-flow 目标还解决了文化和社会需求，例如防止盐害和河口堵塞，以及保护木制基础设施管理设施。虽然日本河流的特点是流量波动大和突然达到峰值，但很少讨论考虑流量变化的 e-flow 评估方法。这是因为日本河流流域上的大坝仅控制了总径流量的一小部分。