Consultant Report Project Number: 45206-001 September 2020 Nepal: Water Resources Project Preparatory Facility Flood Forecasting and Early Warning System: Lakhandei Basin This document is being disclosed to the public in accordance with ADB's Access to Information Policy. GOVERNMENT OF NEPAL Miniistry of Energy, Water Resources and Irrigation Department of Water Resources and Irrigation WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin 4 April 2019 Mott MacDonald 22 Station Road Cambridge CB1 2JD United Kingdom T +44 (0)1223 463500 F +44 (0)1223 461007 mottmac.com WRPPF: Preparation of 1243 124 124 C:\Users\Erik Klaassen\Documents\Work\01 Project\WRPPF - 383877 MM - Nepal\04 PriorityDeliverables\11 River FFEWS\Lak handei\1\190404Basins FFEWS Lakhandei.docxFlood Risk ManagementMott MacDonald Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin 4 April 2019 Mott MacDonald Limited. Registered in England and Wales no. 1243967. Registered office: Mott MacDonald House, 8-10 Sydenham Road, Croydon CR0 2EE, United Kingdom Mott MacDonald | WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin Issue and Revision Record Revision Date Originator Checker Approver Description 01 23/11/18 Iqbal C. Hetmank C. Hetmank 1st submission Hassan D. Ocio 02 04/04/19 Iqbal Peter Ede C Hetmank Final Submission Hassan A Akindiji Audrey Despinasse Document reference: 383877 | REP | 0038 Information class: Standard This document is issued for the party which commissioned it and for specific purposes connected with the above- captioned project only. It should not be relied upon by any other party or used for any other purpose. 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For the avoidance of doubt this Report does not in any way purport to include any legal, insurance or financial advice or opinion. 383877 | REP | 0038 | 4 April 2019 Flood Forecasting and Early Warning System: Lakhandei Basin Mott MacDonald | WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin Contents Executive summary 3 1 Introduction 8 1.1 Project background 8 1.2 Problem statement 8 1.3 Understanding needs of FFEWS 9 1.4 Study area 9 1.5 River system in the basin 11 1.6 CDMA and GSM coverage in Nepal 14 2 Hydro meteorological data 16 2.1 Introduction 16 2.2 Hydro-meteorological gauge densities in Nepal and other countries 17 2.3 Existing hydro-meteorological network Nepal 17 2.3.1 Rainfall 17 2.3.2 Evaporation 18 2.3.3 Temperature 18 2.4 Water level stations 18 2.5 Discharge stations 18 2.6 Gridded Meteorological data 18 2.6.1 APHRODITE precipitation data 19 2.6.2 TRMM3B42 Precipitation 19 2.6.3 MODIS Snow Cover Data 19 2.7 Forecasted Meteorological data 20 2.8 Summary of availability of data 20 3 DHM and existing flood forecasting models 22 3.1 DHM’s mandate 22 3.2 Existing flood forecasting models in Nepal – an overview 23 3.3 Examples of operational flood forecasting models from other countries 23 3.4 Dissemination of forecasts 24 4 Flood forecasting modelling 25 4.1 Flood forecasting modelling framework 25 4.2 Objectives of flood forecasting modelling 26 4.3 Gauge-to-gauge correlation 27 4.4 Hydrological modelling 27 4.5 Routing modelling 28 4.6 Hydrodynamic modelling 28 383877 | REP | 0038 | 4 April 2019 Flood Forecasting and Early Warning System: Lakhandei Basin Mott MacDonald | WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin 4.7 Modelling software 29 4.8 Modelling software comparative list 30 4.9 FFEWS cost consideration 30 5 Rain gauge network design 32 5.1 Introduction 32 5.2 Auto telemetry rain-gauge 32 5.2.1 Description 32 5.2.2 Time of observation 33 5.2.3 Operation and measurement 33 5.2.4 Data transmission, storage and archive 34 5.3 Radar rain gauge 34 5.3.1 Description 34 5.3.2 Specification 34 5.4 Rain gauge network recommended for installation 35 5.5 Budgets for proposed rain gauge network installation 37 6 Hydrometric network design 38 6.1 Water level gauge network 38 6.1.1 Description 38 6.1.2 Time of observation 39 6.1.3 Operation, measurement and maintenance 39 6.1.4 Data transmission, storage and archive 39 6.2 Discharge measurement station 39 6.2.1 Description 39 6.2.2 Discharge measurement equipment 39 6.2.3 Cableway flow measurement 40 6.2.4 Equipment budget for discharge measurement 41 6.3 Hydrometric gauge recommended for installation 42 6.4 Hydrometric gauging network budget 44 7 Topographic and asset survey 45 7.1 Topographic survey 45 7.2 Survey budget 46 7.3 Satellite imagery 46 8 Flood forecasting model development 47 8.1 Mathematical modelling 47 8.2 Rationale for different forecasting approaches 48 8.3 Gauge to gauge correlation 49 8.4 Hydrological modelling 51 8.4.1 Review of existing data and models 52 8.4.2 Catchment delineation 52 383877 | REP | 0038 | 4 April 2019 Flood Forecasting and Early Warning System: Lakhandei Basin Mott MacDonald | WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal Flood Forecasting and Early Warning System: Lakhandei Basin 8.4.3 Hydrological input: Rainfall, temperature and evapotranspiration 53 8.4.4 Bias correction 53 8.4.5 Calibration 53 8.4.6 Validation 54 8.5 Combined rainfall-runoff and gauge-to-gauge correlation 54 8.6 Pure 2-d modelling 55 8.7 1-d modelling 55 8.7.1 River network 55 8.7.2 Calibration and validation 57 8.8 1d/2d linked modelling 58 8.9 Operation of forecasting model 59 8.9.1 Key tasks 59 8.9.2 Real-time data transmission and maintenance 60 8.9.3 Existing forecast model operating system within DHM 61 8.9.4 Delft-FEWS 62 8.9.5 Dissemination of forecast 63 8.9.6 Data assimilation 63 8.10 Evaluation of forecast 64 8.11 Model development schedule 64 8.12 Model development budget 65 8.13 Person-months for experts 66 References 68 Appendices 70 A. Modelling software comparison 71 B. Comments and responses 74 383877 | REP | 0038 | 4 April 2019 Flood Forecasting and Early Warning System: Lakhandei Basin Mott MacDonald | WRPPF: Preparation of Priority River Basins Flood Risk Management Project, Nepal 1 Flood Forecasting and Early Warning System: Lakhandei Basin List of abbreviations ADB - Asian Development Bank ASCE - American Society of Civil Engineers CBA - Cost Benefit Analysis CBDRM - Community Based Disaster Risk Management CDMC - Community Disaster Management Committee DDC - District Development Committee DDRC - District Disaster Relief Committee DEM - Digital Elevation Model DEOC - District Emergency Operation Centre DHM - Department of Hydrology and Meteorology DMF - Design and Monitoring Framework DoWRI - Department of Water Resources and Irrigation DPR - Detailed Project Report DWIDM - Department of Water Induced Disaster Management EARF - Environmental Assessment Review Framework EIA - Environmental Impact Assessment EIRR - Economic Internal Rate of Return EMP - Environmental Management Plan EPR - Environmental Protection Rule EWS - Early warning system FFEW - Flood forecasting and early warning FHRMP - Flood Hazard Mapping and Risk Management Project FIRR - Financial Internal Rate of Return FMA - Financial Management Assessment GDP - Gross Domestic Product GESI - Gender and social inclusion GFS - Global forecast system GIS - Geographic information system GLOF - Glacier Lake Outburst Flood GoN - Government of Nepal GPS - Global Positioning System ICIMOD - International Centre for Integrated Mountain Development IEE - Initial Environmental Examination IP - Indigenous People IPP - Indigenous People Plan IPPF - Indigenous People Plan Framework IRP - Involuntary Resettlement Plan IRPF - Involuntary Resettlement Plan Framework LDC - Least Developed Countries MoHA - Ministry of Home Affairs MoEWRI - Ministry of Energy, Water Resources and Irrigation MOUD - Ministry of Urban Development NAPA - National Adaptation Programme of Action NEOC - National Emergency Operation Centre NPR - Nepalese Rupiah NPV - Net Present Value OPEC - Organization of the Petroleum Exporting Countries 383877 | REP | 0038 | 4 April 2019 Flood Forecasting and Early Warning System: Lakhandei Basin Mott MacDonald | WRPPF: Preparation of