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Introduction to the GRM model

The Grid-based rainfall–Runoff Model (GRM) is a physically based distributed model used for simulating rainfall–runoff events and continuous runoff simulation. A kinematic wave model is used to analyze overland and channel flow and the Green–Ampt model is used to calculate infiltration. It simulates interception, evapotranspiration, snow melt, overland flow, channel flow, subsurface flow, base flow, and controlled flow by stream facilities. The finite volume method is used to discretize governing equations and the Newton–Raphson method is used for nonlinear terms.The development history of the GRM is as follows.

• The GRM was first developed in 2008. It could simulate overland flow, channel flow, subsurface flow, and controlled flow by stream facilities. The model was developed as HyGIS-GRM, an add-on for Hydro Geographic Information System (HyGIS), and was operated as an extension menu under HyGIS.
• In 2010, the base flow simulation was added. Moreover, a real-time flow analysis module using real-time rainfall data was developed.
• In 2012, a multi-site calibration method for single watersheds was developed.
• In 2014, infiltration, subsurface flow, and base flow simulation methods were improved and the MW-GRM plug-in that could run on MapWindow GIS (v.4.8.8), an open source GIS, was developed.
• In 2015, the sensitivity of the calculation time step (dt) was improved. Moreover, the real-time flow analysis module was improved to allow simulations of the real-time flow control. A multi-site calibration method that allowed coupled analysis of multiple watershed systems was developed.
• In 2017, the GRM was separated from GIS and graphic user interfaces (GUIs) and was developed into an independent executable file. In addition, a parallel computation method using .NET and a method that could change the calculation time step (dt) during simulation were developed.
• In 2018, QGIS pluin GUI that could run on QGIS, an open source GIS, was developed. The GRM model codes were converted from Visual Basic .NET into C#.
• In 2020, the model was improved to enable setting of multiple channel information. Options for real-time simulation was added. The GRM model using C++ was developed.
• In 2021, the model was improved to enable more detailed simulation of reservoir operation.
• In 2022, interception, evapotranspiration, and snow melt simulation modules were added for continuous runoff simulation.

The GRM is continuously being developed by Korea Institute of Civil Engineering and Building Technology. A stability improvement of the model, addition of functions, and development of modeling softwares are currently in progress.

GRM GUI

• GRM GUI was developed as integrating the GRM v2016 with GUI, and released as MapWindow 4.8.8 plug-in (MW-GRM).
• The GRM v2017 and over are not supported in the MW-GRM.
• From GRM v2018, the GRM GUI for QGIS plug-in (QGRM) has been provided.
  (https://github.com/floodmodel/Plugin_repository_QGIS3.10/tree/main/QGRM)

Pre and post-processing tools

The GRM uses many topographical and spatial data established based on a DEM, soil and land cover maps, and rainfall raster file as input data. Pre- and post-processing tools consist of Drainage Tools and GRM Tools and provide various functions to make the GRM input files and to process raster files.

1. ALTEK Tool

• ALTEK Tool includes various functions for pre- and post-processing of many input and output files.
• Raster file conversion, raster file clipping and resampling, and editing text file.
• Extracting information from raster time series data, simple algebraic and conditional calculations.
• https://github.com/swallowWings/ALTEK/tree/master/DownloadStableVersion
• Setting and starting guideline : https://github.com/swallowWings/ALTEK/tree/master/DownloadStableVersion/ALTEK_SettingAndStarting_Guideline.pdf

2. Drainage Tools

• The watershed, slope, flow direction, flow accumulation, stream network raster files generated in DEM analyses can be created using the Drainge Tools (QGIS plugin).
• TauDEM and GDAL were used.
• https://github.com/floodmodel/Plugin_repository_QGIS3.10/tree/main/QGIS_Drainage

Download

Latest version

• GRM model
  Including the GRM2018 model, sample data, manual, source code
  Download at https://github.com/floodmodel/GRM/tree/master/DownloadStableVersion

QGRM

• QGIS plugin GUI of GRM model
  Download at https://github.com/floodmodel/Plugin_repository_QGIS3.10/tree/main/QGRM

Pre- and post-processing tools

• QGIS plug-ins of drainage Tools for DEM processing. Download at https://github.com/floodmodel/Plugin_repository_QGIS3.10/tree/main/QGIS_Drainage
• ALTEK tool. Download at https://github.com/swallowWings/ALTEK/tree/master/DownloadStableVersion