Analysis of precipitation and water level elements for typical floods in the Taihu Lake Basin

In this study, we comprehensively compared the flood in 2020 with three historical floods in 2016, 1999 and 1991 in the Taihu Lake Basin, and analyzed the similarities and differences of the precipitation and water level elements corresponding to the four floods. It was found that in terms of the time distribution, the flood-causing precipitation processes in 1991, 1999 and 2016 were relatively concentrated but with intermittent periods, while the flood-causing precipitation in 2020 could be regarded as a continuous precipitation process, with a larger cumulative rainfall but a more uniform time distribution. In terms of the spatial distribution, the flood-causing precipitation in 1991 and 2016 were “Northern Type”, with precipitation in the northern sub-areas in the Taihu Lake Basin significantly higher than other sub-areas. However, the flood-causing precipitation in 1999 was “Southern Type”, with precipitation in the southern sub-areas higher than other sub-areas. However, in 2020, the flood-causing precipitation had different spatial distribution, with relatively small gaps among all the sub-areas. Influenced by the precipitation process, the water level of the Taihu Lake for the floods in 1991, 1999 and 2016 had a remarkable fall or a stable period. However, for the flood in 2020, it showed a continuous increasing process. During the flood period in 2020, the highest water level at the representative gauges in the southern sub area of Zhexi obviously exceeded that in 1991 and 2016, but the water level situation in the northern sub-areas of Huxi and Wuchengxiyu was less severe than in 1991, 1999 and 2016. In general, the intensity of floods in the Taihu Lake Basin in 2020 was lower than that in 1999 and other two years, and its disaster losses were also significantly smaller. However, the flood in 2020 was still of important value to the rainstorm and flood design and operation in the Taihu Lake Basin and its sub-areas.