自由流动的河流：亚行资助项目的筛选和评估指南（英）

SCREENING AND ASSESSMENT GUIDANCEFOR ADB-FINANCED PROJECTS DECEMBER 2025 FREE-FLOWING RIVERS SCREENING AND ASSESSMENT GUIDANCEFOR ADB-FINANCED PROJECTS DECEMBER 2025 Creative Commons Attribution 3.0 IGO license (CC BY 3.0 IGO) © 2025 Asian Development Bank6 ADB Avenue, Mandaluyong City, 1550 Metro Manila, PhilippinesTel +63 2 8632 4444; Fax +63 2 8636 2444www.adb.org Some rights reserved. Published in 2025. ISBN 978-92-9277-618-3 (print); 978-92-9277-619-0 (electronic); 978-92-9277-620-6 (ebook)Publication Stock No. TIM250543-2DOI: http://dx.doi.org/10.22617/TIM250543-2 The views expressed in this publication are those of the authors and do not necessarily reflect the views and policiesof the Asian Development Bank (ADB) or its Board of Governors or the governments they represent. ADB does not guarantee the accuracy of the data included in this publication and accepts no responsibility for anyconsequence of their use. The mention of specific companies or products of manufacturers does not imply that theyare endorsed or recommended by ADB in preference to others of a similar nature that are not mentioned. By making any designation of or reference to a particular territory or geographic area in this document, ADB does notintend to make any judgments as to the legal or other status of any territory or area. This publication is available under the Creative Commons Attribution 3.0 IGO license (CC BY 3.0 IGO)https://creativecommons.org/licenses/by/3.0/igo/. By using the content of this publication, you agree to be boundby the terms of this license. For attribution, translations, adaptations, and permissions, please read the provisionsand terms of use at https://www.adb.org/terms-use#openaccess. This CC license does not apply to non-ADB copyright materials in this publication. If the material is attributedto another source, please contact the copyright owner or publisher of that source for permission to reproduce it.ADB cannot be held liable for any claims that arise as a result of your use of the material. Please contact pubsmarketing@adb.org if you have questions or comments with respect to content, or if you wishto obtain copyright permission for your intended use that does not fall within these terms, or for permission to usethe ADB logo. Corrigenda to ADB publications may be found at http://www.adb.org/publications/corrigenda. FIGURES AND BOXABBREVIATIONS 1INTRODUCTION1.1Context 2.1Definition of a Free-Flowing River22.2Identification Approach22.3Data Verification Tasks32.4 Method Refinements Reflecting Ecological Priorities6 3SCREENING AND DUE DILIGENCE GUIDANCE FOR PROJECTS POTENTIALLY7AFFECTING FREE-FLOWING RIVERS 3.1Phase 1: Project Screening73.2Phase 2: River Screening93.3Phase 3: Regional Connectivity Impact Screening11 REFERENCES14 Figures and Box Figures 1Example of River Feature of Misidentification32Imagery-Based Review of Mapped River Courses43Outlet Recognition and Connectivity Mapping44Valmikinagar Barrage on the Kali Gandaki River, Nepal, Constructed in 197055Construction Site of Arun 3 Hydropower Project on Arun River (Nepal)66Phase 1—Project Screening77Phase 2—River Screening98Extent of Fragmentation Impacts of a Barrier11 Box Key Provisions of Environmental and Social Standard 6 Abbreviations ADBAsian Development BankCSIConnectivity Status IndexDEMdigital elevation modelEFlowsenvironmental flowsESFEnvironmental and Social FrameworkESSEnvironmental and Social Standardkmkilometersm³/scubic meters per secondMARmean annual runoff 1.1Context The Asian Development Bank (ADB) Environmental and Social Framework (ESF, 2024) sets out requirementsto avoid and manage risks to biodiversity and natural resources. Under Environmental and Social Standard 6(ESS6), certain areas of critical habitat receive heightened protection. Para. 23 identifies three categories thattrigger stricter financing constraints: (i) Alliance for Zero Extinction sites; (ii) the United Nations Educational,Scientific and Cultural Organization’s Natural and Mixed World Heritage Sites; and (iii) free-flowing rivers thatare 500 kilometers (km) or longer. In line with ESS6 paras. 21–24, ADB does not finance activities that wouldresult in adverse impacts on these areas, except under narrowly defined circumstances consistent with ESS6(e.g., conservation-related activities or as otherwise provided under para. 24) (Box). Free-flowing rivers≥500 km.For ESS6 para. 23(iii), ADB applies a definition and screening method to identifyrivers that remain largely unaffected by human-made changes to flow and connectivity for at least500 km;either from major source(s) to mouth (including estuaries, large lakes, or inland seas) or for≥500 km upstreamof an estuary or ocean. This approach builds on Grill et al. (2019) with methodological updates (e.g., improvedriver paths, updated barrier information, and recognition of diadromous migration routes and significanttributary contributions). A definition and identification framew