Enhancing the capabilities of the Chao Phraya forecasting system through the integration of pre-processed numerical weather forecasts

Theerapol Charoensuk*, Jakob Luchner, Nicola Balbarini, Piyamarn Sisomphon, Peter Bauer-Gottwein

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Study region: This study focuses on the Chao Phraya (CPY) Basin, Thailand.

Study focus:
This study aims to improve the skill of the CPY flood forecasting system, developed by Hydro-Informatics Institute (HII) and DHI A/S since 2012. It introduces two pre-processing workflows that are applied to the raw numerical weather prediction (NWP) provided by Weather Research and Forecasting model (WRF): quantile mapping bias correction (QM) and random forest regression (RF). Rainfall forecasts, updated with two pre-processing methods, WRF-QM and WRF-RF, were evaluated against daily rainfall measurements from HII's stations in each subcatchment. Six hydrological re-forecasting experiments were conducted using a hydrological model to compare runoff forecasts with and without preprocessing method as well as with in-situ rainfall, climatology and persistence benchmark. We assessed rainfall and runoff predictions during training (2016–2019) and testing periods (2020–2021).

New Hydrological Insights for the Region:
Utilizing pre-processing methods in rainfall prediction enhances the accuracy for raw rainfall and runoff predictions. The WRF-QM and WRF-RF methods improved rainfall prediction by 12% and 18% in RMSE's terms during testing period, respectively. Overall performance results indicate runoff forecasting with WRF-QM and WRF-RF pre-processing reduces RMSE by 34% and 40%, respectively, compared to Raw WRF. Wilcoxon signed-test confirmed significant improvement with pre-processing methods. Our study demonstrates the potential of pre-processed NWP to enhance the skill of hydrologic forecasting systems. Pre-processing methods boost flood forecasting reliability, addressing challenges caused by more frequent and severe hydrologic extremes.
Original languageEnglish
Article number101737
JournalJournal of Hydrology: Regional Studies
Volume52
Number of pages10
ISSN2214-5818
DOIs
Publication statusPublished - 2024

Keywords

  • Chao Phraya
  • Flood forecasting
  • Performance
  • Uncertainty
  • Hydrologic model
  • Thailand

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