Draft for Comments Please do not quote Report on Hydrological Modeling – Current Status and Future Directions Prepared for the Center for Excellence in Hydrological Modeling at NIH National Hydrology Project National Institute of Hydrology Roorkee Version 1.0 July 2017 LIST OF CONTENTS Title Page No. CHAPTER-1 SURFACE WATER MODELLING RAINFALL-RUNOFF MODELLING, FLOOD MODELLING AND URBAN HYDROLOGY .................................................................................... 1-67 1.1 Introduction ............................................................................................................................................. 1 1.2 Brief History of Hydrological Models .................................................................................................... 2 1.3 Classification of Hydrological Models ................................................................................................... 4 1.4 Temporal and spatial scale in hydrological modeling............................................................................. 9 1.4.1 Hydrological processes and observational scales ........................................................................ 9 1.5 Hydrological Modelling (Working) Scale ............................................................................................ 11 1.5.1 Point scale .................................................................................................................................. 13 1.5.2 Micro-scale ................................................................................................................................ 13 1.5.3 Meso-Scale ................................................................................................................................. 13 1.5.4 Macro-Scale ............................................................................................................................... 14 1.6 Hydrological Processes and Runoff Routing considered in Runoff Assessment .................................. 14 1.6.1 Physical processes considered in hydrological model ............................................................... 15 1.6.2 Spatial hydrological model structure: spatial discretization ...................................................... 17 1.7 Causes of Flood and Special Flood Problems ....................................................................................... 20 1.8 River Bank/Bed Erosion and Sediment Transport ................................................................................ 20 1.9 Dam Break Flows ................................................................................................................................. 20 1.10 Flash Floods ........................................................................................................................................ 21 1.11 Real-Time Flood Forecasting.............................................................................................................. 21 1.12 Model Calibration and Validation ....................................................................................................... 21 1.12.1 Calibration methods ................................................................................................................. 23 1.12.2 Model validation ...................................................................................................................... 23 1.12.3 Performance validation ............................................................................................................ 25 1.12.4 Advanced techniques and general guidelines for model calibration and validation ................ 25 1.12.5 Guidelines for model performance validation .......................................................................... 27 1.13 Uncertainty Analysis ........................................................................................................................... 27 1.13.1 Commonly used uncertainty estimation techniques ................................................................. 30 1.14 Data Requirement for Rainfall-runoff and Flood Modelling .............................................................. 31 1.14.1 Rainfall characteristics ............................................................................................................. 31 1.14.2 Infiltration and other loss characteristics ................................................................................. 33 1.14.3 Streamflow characteristics ....................................................................................................... 33 1.14.4 Watershed characteristics ......................................................................................................... 33 1.15 Hydrological Modeling Softwares for Rainfall-Runoff and Flood Modelling ................................... 35 1.16 Floods in Urban Areas ........................................................................................................................ 43 1.16.1 Flood flow analysis .................................................................................................................. 45 1.16.2 Design discharge formulae ....................................................................................................... 45 1.16.3 Urban hydrology models .......................................................................................................... 47 1.17 Remarks .............................................................................................................................................. 47 1.18 Way Forward ...................................................................................................................................... 50 CHAPTER-2 SUBSURFACE WATER MODELING – FLOW AND CONTAMINANT TRANSPORT .................................................................................................................................... 68-124 2.1 Introduction ........................................................................................................................................... 68 2.1.1 General ....................................................................................................................................... 68 2.1.2 Hydrogeological settings of India .............................................................................................. 68 2.1.3 Rainfall and groundwater resources of India ............................................................................. 70 2.1.4 Groundwater related issues in India ........................................................................................... 70 2.1.5 How modeling can help groundwater management? ................................................................. 72 2.1.6 Issues related to modeling .......................................................................................................... 72 2.1.7 Modeling as the management tool ............................................................................................. 72 2.2 Subsurface Modeling ............................................................................................................................ 73 2.2.1 General ....................................................................................................................................... 73 2.2.2 Issues Related to sub-surface zone Modeling ............................................................................ 74 2.2.3 What Groundwater models can do? ........................................................................................... 75 2.3 Unsaturated/Vadose Zone Modeling .................................................................................................... 76 2.3.1 General ....................................................................................................................................... 76 2.3.2 Governing equations of water and transport in unsaturated soils .............................................. 76 2.3.3 Input data for unsaturated zone modeling .................................................................................. 77 2.3.4 Modeling of unsaturated Flow ................................................................................................... 79 2.3.5 Modeling of solute transport through unsaturated zone ............................................................. 81 2.3.6 Unsaturated zone modeling software ......................................................................................... 81 2.3.7 Concluding remarks ................................................................................................................... 83 2.4 Groundwater Modeling Process ............................................................................................................ 83 2.4.1 General ....................................................................................................................................... 83 2.4.2 Steps associated in modeling ..................................................................................................... 83 2.4.3 Flow and transport processes ..................................................................................................... 85 2.4.4 Governing equations .................................................................................................................. 85 2.4.5 Classification of groundwater models .......................................................................................