Environmental flow (e-flow) practices were investigated for 100 class A rivers in Japan, which are managed by the central government. We examined how much e-flow requirements (EFRs) are allocated for each river, and investigated the seasonally variable flow components, objectives, and target organisms. The EFRs of the 100 rivers ranged from 5 to 51% as a percentage of the mean annual discharge (MAD). Protecting physical habitat was an e-flow objective for all target rivers. Protecting water quality and cultural scenery, preventing salt damage, and maintaining groundwater levels were also common objectives. However, the minimum flow required for the migration and spawning of 12 representative fish species was the most influential factor. The Japanese e-flow framework is a holistic approach that takes not only individual species but also multiple aspects of ecosystem services, including its social and cultural value, into account. E-flows for all target rivers were given as a form of minimum flow. Eighty-six percent of the rivers considered seasonally variable flow targets, while 14% designed constant minimum flow throughout a year. The reason why the EFRs do not consider natural flow variability is that the storage and control capacity of Japanese dams is minimal, and that problems associated with the modified flow regime is not critical at present. The Japanese e-flow framework has been successfully implemented, and it has been institutionally integrated into river management for 30 years. However, it will require adaptive management and adjustment in the future as social structure, climate, and hydro-ecological characteristics change.

中文翻译：

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日本 100 条主要河流的比较研究：多目标评估和环境流量实践

对由中央政府管理的日本 100 条 A 级河流的环境流量（e-flow）实践进行了调查。我们检查了为每条河流分配了多少电子流量要求 (EFR)，并调查了季节性变化的流量成分、目标和目标生物。100 条河流的 EFR 占平均年流量 (MAD) 的百分比从 5% 到 51% 不等。保护自然栖息地是所有目标河流的 e-flow 目标。保护水质和文化景观、防止盐害和维持地下水位也是共同的目标。然而，12 种代表性鱼类迁徙和产卵所需的最小流量是最有影响的因素。日本的电子流框架是一种整体方法，不仅考虑到单个物种，而且考虑到生态系统服务的多个方面，包括其社会和文化价值。所有目标河流的 E 流量均以最小流量的形式给出。86% 的河流考虑了季节性可变流量目标，而 14% 的河流设计了全年恒定的最小流量。EFR 不考虑自然流量变化的原因是日本大坝的蓄水和控制能力很小，与修改后的流态相关的问题目前并不严重。日本e-flow框架已成功实施，并已在制度上融入河流管理30年。然而，