Impacts of more extreme climate on daily hydrological-atmospheric processes and implications for long-term water availability in the East River (Dongjiang) basin

Many cities around the world are expected to face greater challenges of water supplies and hazard prevention under more extreme climate due to global warming. Many previous studies have evaluated the climate change impacts on water resources mostly at longer time scales, such as monthly, seasonal, and annual. However, much fewer efforts have been made to study the impacts of more extreme climate (e.g. more intensive heavy precipitation and longer dry spells) characterized by increasing short-term temporal variability on hydrological-atmospheric processes (e.g. soil-vegetation-atmosphere interactions and runoff generation), and the implications of these changes for long-term water availability and reservoir operations. The East River basin is a water-rich region dominated by sub-tropical and humid monsoon climate, but water resources of the basin have already been heavily developed and allocated to meet the tremendous water demands to support about 40 million people and rapid economic growth in the Pearl River Delta region, making this region particularly vulnerable for changes in long-term water availability. Therefore, a rigorous assessment of the impacts of more extreme climate on daily hydrological-atmospheric processes and implications for water availability and reservoir operations is crucial for the sustainable water resources development and management in the East River basin under climate change. The proposed study will configure the state-of-the-art fully coupled hydrological-atmospheric model system WRF/WRF-Hydro for the East River basin with consideration of the dynamic interactions among the three components of the soil-vegetation-atmosphere continuum. The model system will be first calibrated and validated using historical observation data. Hypothetical climate scenarios of different extreme levels with the same total/mean climatic variables will be constructed to drive WRF/WRF-Hydro to simulate and evaluate the short-term hydrological-atmospheric processes, the changes in long-term water availability and the effectiveness of water storage of reservoirs under the more extreme climate. The objectives of the proposed study are: (1) to characterize the changes in daily hydrological-atmospheric processes, e.g. runoff generation and soil-vegetation-atmosphere feedback, in the East River basin under more extreme climate; (2) to evaluate the responses of long-term water availability and its linkages with daily hydrological-atmospheric processes in more extreme climate, and; (3) to assess the impacts of temporal redistributions of water availability on the effectiveness of water storage of reservoirs. This study is expected to contribute significantly to the scientific understanding of the hydrological impacts of climate change at different temporal scales, but also carry valuable practical significance and enormous relevance to water security in Hong Kong and its neighboring cities.