ESTABLISHMENT OF END-TO-END FLOOD EARLY WARNING SYSTEM IN KOSHI AND WEST RAPTI RIVER BASINS IN NEPAL Inception Report Dept. of Hydrology & Meteorology Inception Report June 2017 63800912 inception report version 3/ HCA / 2017-06-30 This report has been prepared under the DHI Business Management System certified by Bureau Veritas to comply with ISO 9001 (Quality Management) Approved by Flemming Jakobsen Dept. of Hydrology & Meteorology Inception Report June 2017 ESTABLISHMENT OF END-TO-END FLOOD EARLY WARNING SYSTEM IN KOSHI AND WEST RAPTI RIVER BASINS IN NEPAL Inception Report Prepared for Dept. of Hydrology & Meteorology Represented by Dr. Rishi Ram Sharma, Director General Koshi embankment Photo by DTL Report authors Team-Leader Hans Christian Ammentorp, Deputy Team Leader Khada Nanda Dulal Project manager Flemming Jakobsen Quality supervisor Oluf Jessen Project number 63800912 Approval date 04-07-2017 Revision 3.0 Classification Open DHI (India) Water & Environment Pvt Ltd•NSIC Bhawan, IIIrd Floor, NSIC - STP Complex•Okhla Industrial Estate•IN- 11 00 20New Delhi• India Telephone: +91 11 4703 4500 • Telefax: +91 11 4703 4501 • • www.dhigroup.com 63800912 inception report version 3/ HCA / 2017-06-30 CONTENTS 1 Executive summary ..................................................................................................... 4 2 Introduction ................................................................................................................. 5 2.1 Background .................................................................................................................................... 5 2.2 Study basins ................................................................................................................................... 5 2.2.1 Koshi River basin ........................................................................................................................... 5 2.2.1.1 Issues of Flooding in Koshi ............................................................................................................ 7 2.2.2 West Rapti River basin .................................................................................................................. 7 2.2.2.1 Issue of flooding in West Rapti basin ............................................................................................. 8 2.3 Inception phase activities ............................................................................................................... 9 2.4 Structure of the Report ................................................................................................................... 9 3 Literature Review ...................................................................................................... 10 3.1 DHM’s role in flood forecasting and early warning ...................................................................... 10 3.2 Glacial lake outburst flood (GLOF) early warning system for Tsho Rolpa................................... 11 3.3 Flood early warning system on the Bhote Koshi .......................................................................... 12 3.4 Community-based flood early warning systems .......................................................................... 12 3.5 ICIMOD’s contribution in flood early warning ............................................................................... 12 3.6 Efforts made by Department of Water Induced Disaster Management (DWIDM) ....................... 13 4 Data availability ......................................................................................................... 14 4.1 Topographical data ...................................................................................................................... 14 4.2 Hydro-meteorological data ........................................................................................................... 14 4.2.1 Koshi River basin ......................................................................................................................... 15 4.2.2 West Rapti River basin ................................................................................................................ 19 4.2.3 Satellite rainfall products as supplementary rainfall data............................................................. 21 4.2.4 Handling missing rainfall data ...................................................................................................... 22 5 Approach and Methodology ..................................................................................... 23 5.1 Task 1 .......................................................................................................................................... 23 5.1.1 Structure of an Early Warning System and assessment approach ............................................. 24 5.1.1.1 Risk Knowledge ........................................................................................................................... 24 5.1.1.2 Monitoring and Warning Service .................................................................................................. 24 5.1.1.3 Dissemination and Communication ............................................................................................. 25 5.1.1.4 Response Capability .................................................................................................................... 25 5.1.1.5 Field visits .................................................................................................................................... 25 5.2 Task 2 .......................................................................................................................................... 26 5.3 Task 3 .......................................................................................................................................... 27 5.4 Task 4 .......................................................................................................................................... 27 5.4.1 Data collection and processing .................................................................................................... 27 5.4.2 Hydrologic modelling .................................................................................................................... 28 5.4.2.1 Data for hydrological modelling .................................................................................................... 28 5.4.3 Hydrodynamic modelling .............................................................................................................. 30 5.4.4 Real-time updating ....................................................................................................................... 31 5.4.5 Model calibration .......................................................................................................................... 32 5.4.6 Operational forecasting ................................................................................................................ 33 5.5 Task 5 .......................................................................................................................................... 34 5.6 Task 6 .......................................................................................................................................... 36 5.7 Task 7 .......................................................................................................................................... 36 i 6 Project implementation plan .................................................................................... 38 7 Risks and issues ........................................................................................................ 1 8 References .................................................................................................................. 2 FIGURES Figure 1 Location of Koshi Basin ................................................................................................................. 6 Figure 2 Location of West Rapti basin ......................................................................................................... 8 Figure 3 The network of rainfall and river gauging stations in Koshi basin. .............................................. 15 Figure 4 The network of rainfall and river gauging stations in West Rapti River basin ............................. 19 Figure 5 Preliminary delineation of sub-catchments in the Koshi and West Rapti basins. The triangles represent real-time river gauging stations ..................................................................... 27 Figure 6 MIKE 11 NAM Hydrological model components .......................................................................... 28 Figure 7 The Seamless Weather Generator .............................................................................................. 29 Figure 8 MIKE HYDRO River based map of the January 2015 flood in Malawi ........................................ 30 Figure 9 Sample flexible mesh grid for 2D flow simulation in MIKE FLOOD (Chao Phraya basin, Thailand) ...................................................................................................................................... 31 Figure 10 Example of data assimilation application - top: initial hindcast water levels prior to applying data assimilation, bottom: updated hindcast following data assimilation (i.e. differences between simulated and observed water levels are reduced) resulting in improved water level