Research On Forecasting Techniques Of Qiantang River Tide Based On Grey System Theory

Qiantang River tidal bore was world-famous,but people's life and property safety and engineering facilities along the river were threatened by the fierce power of tidal bore.It is very important to water resource optimization and preventing tide disaster management for scientific decision-making that the high tidal level,the arriving time of tidal bore and the annual maximum tidal level of Qiantang River were predicted accurately.Because the Qiantang River tide was affected by some random uncertainty factors of hydrological,meteorological and others,with it's hydrological data had some characteristics of random and nonlinear,it became very difficult to predict Qiantang River tide.Grey system theory had certain advantages in the study of nonlinear systems.Qiantang River tide forecasting techniques were studied by using historical hydrological data of hydrologic station along the Qiantang River based on Grey system theory for the first time.Specific contents are as follows:1)GM(1,1)model was established,then grey Markov model of high tidal level was also obtained combining with the Markov chain based on historical hydrological data of Yanguan Hydrologic Staion.The results show that the grey Markov model has higher accuracy in the high tidal level prediction of Qiantang River.Finally,the grey Markov model was used to forecast the high tidal level of Zhakou Hydrologic Station for a month.2)The study presented a method of tide detection and propagation delay prediction for predicting the arriving time of tidal bore in the Qiantang River.It determined whether the tidal bore was arriving according to the change characteristics of water level and flow velocity before and after the moment of the tidal bore arriving.Moreover,the model was established by using the original propagation delay data and data transformed by weakening buffer operator respectively.The results show that models established by using data transformed by weakening buffer operator were more accurate and eliminated the interference of the system.3)According to the frequent fluctuation characteristics of annual maximum tidal level of Qiantang River,the annual maximum tidal level prediction was studied based on topology prediction of grey system theory.Taking Ganpu Hydrological Station in the Qiantang River for example,the topology prediction model was used to predictthe annual maximum tidal level in the next several years.The forecast results of the model were tested by the annual maximum tidal level from 2003 to 2014,and the values were forecast from 2015 to 2021.The results show that the model agrees with the measured values,and has higher precision.The forecast results of the annual maximum tidal level in the following years may be used as a reference for preventing tide disasters such as natural disasters in advance.In this paper,the relevant forecasting methods based on Grey system theory are studied on the high tidal level,the arriving time of tidal bore and the annual maximum tidal level of Qiantang River,and the excellent results have been obtained.The forecast methods are characterized by convenience for modeling and high prediction precision.Therefore the methods can provide a certain theoretical foundation for improving forecast accuracy and reliability of information forecast system of Qiantang River tidal bore.