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Abstract:
The extreme hydroclimatic events, such as extreme drought, flood, and drought-flood abrupt alternation (DFAA, defined as a natural phenomenon of sudden wet spells following persistent dry spells), are becoming more frequent and intense in all climatic zones. These hydroclimatic extremes caused by climate change and human activity can pose severe challenges to freshwater ecosystems, which can have significant consequences on the economy and society. For instance, extreme droughts due to insufficient rainfall and/or high temperature would lead to reduced the river flow, slower flow velocity, and decreased dissolved oxygen in water, resulting in increased water pollutants, fish kills, and even the collapse of aquatic ecosystem. The DFAA magnifies the impacts of individual drought and flood events on aquatic ecosystem, which would put excessive strains on the water environment and ecology. Therefore, in this study, it's crucial to investigate the effects of multiple hydroclimatic extremes on the river ecosystem (including the water temperature, dissolved oxygen, nitrogen, phosphorus, and aquatic animals) in order to identify the optimal adaption and mitigation measures. Firstly we identify the different types of extreme hydroclimatic events by adopting widely used indices, such as SPI, SPEI, SRI, etc.. Secondly, applying event coincidence analysis, we explore the correlation, frequency, intensity, and tendency of hydroclimatic extremes. Then by using the copula theory, a two/three dimension joint probabilistic model among indices, water quality, and aquatic animals is proposed.
