Development of an Open Source Software Tool for Climate Change Assessment in Hydrology, SNU-CAHL

Abstract

The Intergovernmental Panel on Climate Change (IPCC) publishes Climate Change Assessment Reports in irregular periods with updated simulations and projections. GCM scenarios are generated and distributed from these reports. With regular updates on these climate change scenarios, hydrologic assessments are frequently required to revise the old projections.

Seoul National University – Climate Change Impact Assessment for Hydrology Library (SNU-CAHL) was created to automate the task of updating the projections for climate change scenarios in hydrology. The overall goal of the library is to support multiple hydrologic models in addition to downscaling models and supporting the automated download of GCM scenarios. The current status of SNU-CAHL is currently a collection of scripts that work together to automate tasks for hydrologic modelling and data management. All scripts were written in the R statistical programming language and SNU-CAHL operates within the R data frames with time-series data values in addition to parameter values for each model. The scripts include support for the IHACRES and GR4J hydrologic model and a basic data abstraction layer that is imported and managed for the datasets within the R data frame as well as an alternative data frame in the form of multiple CSV files. The data abstraction layer is able to import and export GIS raster datasets, which were all converted to and from ASCII. SNU-CAHL now includes an additional script that automates the step that previously required manual involvement using a GIS software. Therefore, all the steps within the SNU-CAHL operation have been automated through scripting.

The use of the software is demonstrated in a case study of the Yongdam Dam Catchment, which is the South-Easternmost catchment of the Geum River Basin. By utilizing the downscaled values from the SNUMM5v3 SNURCM model and the WRF v3.4 RCM model, the applicable use and efficiency of the SNU-CAHL scripts are expressed by the scenarios from January 1st, 2021 to December 31st, 2022. When compared to present precipitation events, the projected precipitation events increase dramatically. Although additional scenarios should be run, the first stage of SNU-CAHL is deemed to be a success. A sample of the Assessment Report 5 was ran through the hydrologic models.