Preliminary Analysis of Tidal Level Change due to River Discharge in the Yangtze River Estuary, China

Wei Chen, Cuiping Kuang, Jie Gu, Xiaodan Mao, Huidi Liang, Honglin Song

Thursday 2 july 2015

14:20 - 14:35h at Europe 2 (level 0)

Themes: (T) Water resources and hydro informatics (WRHI), (ST) Catchment hydrology

Parallel session: 12K. Floodrisk - Assessment

Long-term tidal levels at tidal gauges are frequently used to analyze the sea level change. The sea level records involve glaciers melting, land subsidence, earth surface temperature rise and river discharge change and so on. However, the contribution of these factors on sea level rise is not clear. In this paper, the Yangtze River Estuary is chosen as a prototype to preliminary study the responses of the mean tidal level change to the river discharge. Firstly, MIKE21 is selected as a tool to establish a depth-averaged hydrodynamic model including the Yangtze River Estuary and Hangzhou Bay. Then, this model is well validated with the measured data. After that the validated model is run with different monthly river discharges at Datong station (i.e., tidal limit, about 640 km upstream from the river mouth) from 1950 to 2011. Analysis of monthly river discharges from 1950 to 2011 at Datong station reveals that the monthly river discharge from 1950 to 2003 presents an increasing trend, while decrease from 2004 to 2011 after the impoundment of Three Gorge Dam in 2003 and an extreme drought of the Yangtze River Basin in 2006. The simulations point out that the mean tidal level at Dajishan station (located between the Luchaogang in Shanghai and Shengsi island in Zhejiang Province) is influenced by river discharge with an increasing rate of 0.053 mm/a from 1950 to 2003 and a decreasing rate of 0.056 mm/a from 2004 to 2011. Meanwhile, the increasing rate of mean tidal level (1980-2011) at Dajishan station caused by river discharge only accounts for 5.7%-7.7% of that at sea level bulletin of China (i.e., the value of 3-4 mm/a including the impact of all factors) in the same period.