Drought risk assessments of water resources systems under climate change: a case study in Southern Taiwan

Abstract. This study aims at assessing the impact of climate change on drought risk in a water resources system in Southern Taiwan by integrating the weather generator, hydrological model and simulation model of reservoir operation. Three composite indices with multi-aspect measurements of reservoir performance (i.e. reliability, resilience and vulnerability) were compared by their monotonic behaviors to find a suitable one for the study area. The suitable performance index was then validated by the historical drought events and proven to have the capability of being a drought risk index in the study area. The downscaling results under A1B emission scenario from seven general circulation models were used in this work. The projected results show that the average monthly mean inflows during the dry season tend to decrease from the baseline period (1980–1999) to the future period (2020–2039); the average monthly mean inflows during the wet season may increase/decrease in the future. Based on the drought risk index, the analysis results for public and agricultural water uses show that the occurrence frequency of drought may increase and the severity of drought may be more serious during the future period than during the baseline period, which makes a big challenge on water supply and allocation for the authorities of reservoir in Southern Taiwan.