Abstract: Periodic change of water level in Three Gorges Reservoir is a crucial random variable that affects the deformation and stability of bank slope in the reservoir area. The marginal distribution type, distribution parameters and correlation coefficient of characteristic parameters are obtained by calibrating the water level process lines(WPL) of Three Gorges ranged from 2010 to 2020. Firstly, WPL is fitted with nine straight lines and fourteen parameters inclusive of the duration and rising or falling speed in rising and falling period, the duration of two platforms before and after the main flood period, the climbing and falling durations of flood peak, and the peak water level. AIC (Akaike Information Criterion, AIC) method is used to identify the optimum distribution of characteristic parameters, and statistical uncertainty is simulated by using Bootstrap method. Results show that the WPL formed by average characteristic parameters calibrated from 11-year WPL can effectively avoid the peak elimination and valley filling, and can be taken as typical WPL for deformation and stability prediction of landslides in the reservoir area. The durations of the slow-descent stage and steep-descent stage of decline period and the steep-rising stage and slow-rising stage of the rising period obey Weibull distribution, the extreme value I-type distribution, the lognormal distribution, and the Weibull distribution, respectively, with the mean values being respectively 87.00, 47.45, 22.18, and 32.27 days. The falling or rising speeds of reservoir water in the four stages obey extreme value I-type distribution, Weibull distribution, extreme value I-type distribution, and extreme value I-type distribution, respectively, with the mean values being 14.53 cm/d, 36.75 cm/d, 74.33 cm/d, and 37.88 cm/d, respectively. The Pearson coefficient of correlation between duration and reservoir water level change rate in the four stages are -0.67, -0.78, -0.85, and -0.67. The flood peak level in flood season obeys the extreme value I-type distribution and the mean coefficient of correlation between slow-descent duration and the speed varies largely. The research findings offer random statistical parameters of WPL for risk analysis of landslides in the Three Gorges reservoir area.

Key words: water level process line, characteristic parameters, statistical characteristic, distribution type, correlation, landslide in reservoir area, Three Gorges