Optimization Of Hydrologic Station Netwotk For Input Flood Forecast Of Three Gorge Reservoir And Study On The Application Of Tank Model

It is very important for reservoir operation of Three Gorges to grasp hydrologic information of the upper Yangtze River and have an exact flood forecast result. After storaged water for Three Gorges , 135m storage level has been near Qingxichang, and 175m storage level will be near Cuntan. Now, the spread time of flow for input station to dam has shortened about 24h, it can' t satisfy reservoir operation. So, it is necessary to extend the rang of hydrologic information collection, study on technology of flood forecast, optimize of hydrologic station netwotk for input flood forecast of Three Gorges reservoir, lengthen forecast period and improve the forecast precision.The forecast basin for Three Gorges is more than five hundred thousand square kilometers.This paper introduces the method of optimization of hydrologic station netwotk. 413 hydrologic stations have been selected form 603 stations according to the computed result, so it has optimizated the existing network. It establishes basis for modifying the forecast scheme, studying on the flood forecast technology and improving the forecast precision.Tank model is a conceptive hydrologic model invented by M. Sugawara from Japan in the 1950s and it is a famous basin model used from the 1960s. The characters of Tank model are simple conception, computingconveniently, and structure composed flexibly. In China, a lot of researches have been output about Tank model. In the 1980s , LI Ji-sheng , who was a professor from HoHai University, made a few researches about Tank model in Yellow River and Dongjiang River.Many other departments of hydrology have made many adaptable study on Tank model, too. But up to now, most results are about simulation of run off or exploring researches, Studying in real time flood forecast is very a few .Studying on applying Tank model to real time flood forecast and accumulating experience of application of basin hydrologic model are very necessary for department of hydrology forecast. However, many researches on Tank model are about middle or little basin. Therefore this research is a useful attempt for Tank model applying to large basin. Main river and branch river above Cun Tan are separated many reaches according to the spread time of flow, and every reach is separated many unit reaches according to the calculation time length. The local inflow in every unit reach is computed with Tank model, and the flow of stream is computed with the method of continous Muskingum. The precision of the river system flood forecast model is above 85%, and the result of real time flood forecast is satisfactory .This paper has only introduced the method of making river system flood forecast model during 24h forecast period for Cun tan and Wu long on upper Yangtze River.