Study On The Forecast Model Of High And Low Water Level Of The Yangtze Rivera’s Tidal Reach

The Yangtze River’s Tidal Reach is the reach that between Anhui and Xuliujin, which have a total length of 600 kilometers. This area’s terrain is very flat, elevation is low, and with influence of upstream runoff and offshore tidal. Therefore, it is extremely prone to floods; the high and low water level has a significant impact on people’s production and life. Water level forecasting problems of tidal river have long attracted researchers’ interest and attention, there are already a large number of studies on the tidal river level forecasting, the forecasting of water level in the theories and methods have made some progress and results. But with data summary and analysis on the existing research, we found that there are still have some problems and deficiencies in the existing research results:the traditional model not only have the higher requirements of terrain data, but also have a complicated solution for the equitation, and the prediction accuracy and stability of the model is poor. Therefore, it is necessary to establish the high and low water level forecasting model which are simple and practical, have clear physical concept, and have high precision and high stability.In this paper, with the goal of establishing a high and low water level forecasting model, we make an exploratory research for high and low water level forecasting for the problems and difficulties of existing models in methods and theory:Based on the high and low water level measured data, upstream runoff flow and ebb tide off data, we study the effect of upstream runoff and offshore tide on tidal river’s high and low water level by the statistical methods, consider the impact of flood wave and tidal wave propagation, based on the idea of separation of water, we divide the water level into two parts:daily average water level and tidal wave, respectively, for the daily average water level and tidal waves study fluctuations in the water level, establish a high and low water level model that can meet tidal reach water level’s forecasting.Under the study we take into account the impact of upstream runoff and offshore tidal on tidal reach’s daily average water level, assumption that the average daily tidal river water level only affect by upstream runoff and offshore tidal, ignore other factors, such as storm surges, weather conditions. Based on measured data analysis, we get the relationship between the daily average water level and upstream runoff and offshore tidal data, and establish a tidal river daily average water level forecasting model, the model’s accuracy is able to meet the actual demand, and the model have clearer physical concepts, and the model is simple and stable, suitable for daily average water level forecasting of tidal rivers.In the study of tidal waves, the research unit is four successive tide processes:tide-ebb-tide-ebb. Meticulously to study the relationship of tide difference and ebb difference with upstream river run-off and corresponding tide difference, to establish two tide difference forecasting models of tidal river, by contrast parameter calibration and validation of analytical results, we found that the linear model which has an high accuracy and stability, significantly better than the tidal rate model, therefore, we choose the linear model to predict the tide difference of tidal reach. Period of tide are similar with tide difference. To study the relationship of tide period with upstream run-off and corresponding tide period, to establish tide period prediction model, make an foundation for the high and low water level prediction. The forecasting and validation of both the tide difference model and the tide period model show that the predict accuracy is fit well for the measured data, explained the model’s better consistency, it can be used to forecast the tide difference and tide period.To establish the high and low water level forecasting of tide reach, we base on the daily average water level forecasting model, tide difference and period forecasting model, construct the high and low water level forecasting model of the Yangtze River’s Tidal Reach, and carry out parameter calibration and validation with the measured data. Validation and analytical of the model in Nanjing station and Jiangyin station show that the water level forecasting model by statistical method better than the model based on harmonic analysis method, the forecast accuracy are improved. This study provides a new method for high and low water level prediction.In this paper, using C# language, with the support of GIS, combining with OpenGL, Web Service technologies, we design and develop tidal reach high and low tidal level forecasting system of the Yangtze River. System is mainly to achieve a rapid assimilation of data, reducing the time of traditional manual processing of data, so that data and models to form a chain, to facilitate rapid and sustainable optimization and improvement of forecasting model, lay a foundation for the subsequent tidal reach water level forecasting study.