This discussion paper is a preprint. A revision of the manuscript for further review has not been submitted.
Impact of downscaled rainfall biases on projected runoff changes
Stephen P. Charles1,Francis H. S. Chiew2,Nicholas J. Potter2,Hongxing Zheng2,Guobin Fu1,and Lu Zhang2Stephen P. Charles et al. Stephen P. Charles1,Francis H. S. Chiew2,Nicholas J. Potter2,Hongxing Zheng2,Guobin Fu1,and Lu Zhang2
1CSIRO Land and Water, Floreat WA, 6148, Australia
2CSIRO Land and Water, Canberra ACT, 2601, Australia
1CSIRO Land and Water, Floreat WA, 6148, Australia
2CSIRO Land and Water, Canberra ACT, 2601, Australia
Received: 19 Jul 2019 – Accepted for review: 29 Jul 2019 – Discussion started: 05 Aug 2019
Abstract. Realistic projections of changes to daily rainfall frequency and magnitude, at catchment scales, are required to assess the potential impacts of climate change on regional water supply. We show that quantile-quantile matched (QQM) bias-corrected daily rainfall from dynamically downscaled WRF simulations of current climate produce biased hydrological simulations, in a case study for the State of Victoria, Australia (237 629 km2). While the QQM bias correction can remove bias in daily rainfall distributions at each 10 km2 grid point across Victoria, the GR4J rainfall-runoff model underestimates runoff when driven with QQM bias-corrected daily rainfall. We compare simulated runoff differences using bias-corrected and empirically scaled rainfall for several key water supply catchments across Victoria and discuss the implications for confidence in the magnitude of projected changes for mid-century. Our results highlight the imperative for methods that can correct for temporal and spatial biases in dynamically downscaled daily rainfall if they are to be suitable for hydrological projection.
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Short summary
Assesses suitability of bias-corrected (BC) WRF daily rainfall across state of Victoria, Australia for input to hydrological models to determine plausible climate change impacts on runoff. Compares rainfall and runoff changes using BC WRF with those obtained from empirical scaling (ES) using raw WRF changes. Concludes BC derived changes are more plausible than ES derived changes but that remaining biases in BC WRF daily add uncertainty to runoff projections.
Assesses suitability of bias-corrected (BC) WRF daily rainfall across state of Victoria,...