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WATER AND CLIMATE CHANGE IN THE LOWER MEKONG BASIN WATER AND CLIMATE CHANGE IN THE LOWER MEKONG BASIN: Water & Development Publications - Helsinki University of Technology TKK-WD-06 WATER AND CLIMATE CHANGE IN THE LOWER MEKONG BASIN: Diagnosis & recommendations for adaptation Water and Development Research Group, TKK & Southeast Asia START Regional Center This book together with other project publications is available also electronically at the project’s web site at: http://users.tkk.fi/u/mkummu/water&cc/ ISSN 1797-254X ISBN 978-951-22-9920-1 TKK-WD-06 Water & Development Publications - Helsinki University of Technology www.water.tkk.fi/global/ AB HELSINKI UNIVERSITY OF TECHNOLOGY Water & Development Research Group Water and Climate Change in the Lower Mekong Basin: Diagnosis & recommendations for adaptation Water and Development Research Group, Helsinki University of Technology (TKK), Finland & Southeast Asia START Regional Center (SEA START RC), Chulalongkorn University, Thailand Helsinki University of Technology TKK TKK Water resources research unit P.O. We welcome any comments and feedback on our research: please send them by email to olli.varis@tkk.fi On behalf of the research team, Olli Varis Team Leader Professor, TKK ii CONTENTS Executive summary 1 1 Introduction 5 2 Climate Change Scenarios 7 2.1 Introduction: PRECIS and ECHAM4 2.2 Estimated changes in temperature and rainfall 3 Hydrological Impacts 7 7 9 3.1 Ecosystem functions 3.2 Modelling approach 3.3 Changes in basin-wide hydrology 3.4 Changes in Lower Mekong floodplain 3.4.1 Changes in floodplain water levels 9 11 12 14 14 4 Livelihoods & Local Adaptation Strategies 23 4.1 Tonle Sap 4.1.1 Introduction 4.1.2 Field studies 4.1.3 Findings from the field studies 4.1.4 Summary of the livelihood analysis 4.2 Mekong Delta 4.2.1 Introduction 4.2.2 Key concerns on climate change and changing flood regime 5 Adaptation Policies 5.1 Adaptation policies in Cambodia 5.2 Adaptation policies in Vietnam 5.3 Recommendations on adaptation policies 6 Conclusions and Recommendations 6.1 Climate change scenarios: warmer & wetter 6.2 Hydrological and hydrodynamic changes: changes in flooding 6.2.1 Cumulative impact assessment and the importance of timescales 6.3 Livelihoods & local adaptation strategies: increasing vulnerability 6.4 Overall conclusions & recommendations References 23 23 24 24 28 29 29 29 35 35 35 36 39 39 39 40 42 42 46 iii Annex A: PRECIS Regional Climate Model and its validation 48 Annex B: Future climate projections under two climate scenarios 51 Annex C: Future climate scenarios for the Mekong Delta 55 Annex D: Basin-wide hydrology – VIC model 57 Annex E: Hydrodynamic modelling for floodplains – EIA 3D model E.1 Calibration E.2 Validation results 59 61 61 Annex F: Hydrological impact assesment for the Tonle Sap area F.1 Water levels F.2 Flooded area and flood duration F.3 Summary of the results 63 63 63 70 1 EXECUTIVE SUMMARY INTRODUCTION Current climate change estimates indicate that major environmental changes are likely to occur due to climate change in practically every part of the world, with majority of these changes being felt through modification of hydrological cycle as e.g.