MEKONG RIVER COMMISSION THE COUNCIL STUDY The Study on the Sustainable Management and Development of the Mekong River Basin, including Impacts of Mainstream Hydropower Projects Modelling the Impacts of Climate Change and Development Infrastructure on Mekong Flow, Sediment Regimes and Water Quality Modelling Volume 1: Summary Report January 2018 Disclaimer: These Council Study reports are considered final drafts prepared by the technical experts and specialists of the Mekong River Commission, through a process of consultation with representatives of member countries. The contents or findings of the reports are not necessarily the views of the MRC member countries but will serve as knowledge base and reference in the work of the MRC and its member countries in their ongoing technical and policy dialogues in ensuring the sustainable development of the Mekong river basin. The MRC is funded by contribution from its member countries and development partners of Australia, Belgium, European Union, Finland, France, Germany, Japan, Luxembourg, the Netherlands, Sweden, Switzerland, the United States and the World Bank Council Study Modelling Report Volume 1 of 10 - Summary Report CONTENTS AMENDMENT RECORD This report has been issued and amended as follows: Issue Revision Description Date Prepared By 1 1 Baseline and Main 15 April MRC Modelling Team Sopheap Scenarios 2017 Lim and Anthony Green with contributions by Nguyen Dinh Dat, Ornanong Vonnarat, Rattykone Sayasane, Rachel Blakers and Jorma Koponnen 1 2 Update for May 2017 19 May As above including WUPFIN 2017 1 3 Subscenarios formulation 25 August As above results 2017 1 4 Additional Information for 19 As above ISIS and Subscenarios September results 2017 1 5 Additional Sub Scenario 31 As above results including WUPFIN October and Coastal 2 0 Draft Final Following 25 As above Consultation comments January iii | Page MRC Council Study: Volume 1 Summary Modelling Report v2.0 January 2018 Council Study Modelling Report Volume 1 of 10 - Summary Report CONTENTS Executive Summary ...................................................................................................................................... x 1 Introduction........................................................................................................................................... 1 1.1 Background ................................................................................................................................... 1 1.2 Objectives of the Council Study modelling ............................................................................. 1 1.3 The Mekong Basin (MB) ............................................................................................................ 2 1.4 List of the modelling reports for all model packages ............................................................. 4 2 Modelling Approach and Tools use to simulate and assess the scenario ................................... 5 2.1 Overview of the modelling approach ....................................................................................... 5 2.2 Overview of the modelling process .......................................................................................... 7 3 Description of Simulation Models and Assessment Tools Used in the Council Study ........... 8 3.1 Decision Support Framework (DSF) ....................................................................................... 8 3.1.1 Soil and Water Assessment Tool (SWAT) ...................................................................... 8 3.1.2 Integrated Quantity and Quality Model(IQQM) ........................................................... 9 3.1.3 ISIS Model ............................................................................................................................ 9 3.2 eWater Source Model ................................................................................................................ 11 3.3 WUP-FIN 3D-EIA Model ....................................................................................................... 12 3.4 WUP-FIN Tools and Impact Assessment Tool ................................................................... 12 4 Modelling Scenarios Formulation .................................................................................................... 14 4.1 Background of the Scenarios Formulation ............................................................................ 14 4.1.1 Main Scenarios ................................................................................................................... 14 4.1.2 Sub Scenarios...................................................................................................................... 15 4.2 Data Inputs and Gap Filling .................................................................................................... 16 5 Data Input and Constraints .............................................................................................................. 17 5.1 Requirements of the Council Study for MRC Modelling .................................................... 17 5.2 Requirements for additional modelling .................................................................................. 18 5.3 Sediment and Nutrient Data Analysis and constraints ........................................................ 19 5.4 Channel Data Pakse to Kratie .................................................................................................. 24 5.5 Ground Elevations DEM ......................................................................................................... 25 5.6 Agricultural Modelling ............................................................................................................... 25 5.7 Fisheries and Aquaculture Modelling ..................................................................................... 26 5.8 Sedimentation in Floodplains .................................................................................................. 26 5.9 Coastal Modelling ....................................................................................................................... 26 5.10 Scenario Data .............................................................................................................................. 27 iv | Page MRC Council Study: Volume 1 Summary Modelling Report v2.0 January 2018 Council Study Modelling Report Volume 1 of 10 - Summary Report 5.11 1960s Data ................................................................................................................................... 28 5.12 Sand Mining ................................................................................................................................ 29 5.13 Conclusions on Data Constraints............................................................................................ 29 6 Main and Sub Scenario Results ........................................................................................................ 30 6.1 Land Phase and Irrigation Modelling (SWAT & IQQM) ................................................... 30 6.1.1 Irrigation .............................................................................................................................. 42 6.1.2 Hydropower Production .................................................................................................. 45 6.1.3 Flood Flows in the Upper Basin above Kratie ............................................................. 50 6.2 eWater Source Modelling .......................................................................................................... 51 6.2.1 Source Modelling of Sediment Flux for Main Scenarios ............................................ 51 6.2.2 Sensitivity Analysis of Sediment Trapping Efficiency in Mainstream Dams for 2040 57 6.2.3 Sediment Trapping Sensitivity Results for Changes in LMB Mainstream dams .... 58 6.2.4 Modelling of Nutrient Fluxes .......................................................................................... 59 6.3 ISIS modelling ............................................................................................................................ 61 6.3.1 Changes in Flow and Water level downstream of Kratie ........................................... 61 6.3.2 Salinity Intrusion Modelling ............................................................................................. 66 6.3.3 Flood Modelling and Analysis ......................................................................................... 66 6.3.4 Sediment Modelling in ISIS for Mainstream Dams ..................................................... 69 6.3.5 Sediment Modelling in ISIS for bank erosion, sand mining and overbank sedimentation ...................................................................................................................................... 72 6.4 WUPFIN Tools Application .................................................................................................... 72 6.4.1 Methodology....................................................................................................................... 72 6.5 WUPFIN Tools: Summary of Applications ........................................................................ 73 6.5.1 Impacts on hydrological condition including groundwater........................................ 73 6.5.2 Fisheries Impacts ..............................................................................................................