| Construction diversion is as a subsystem, it plays a strategic role in overall during of the water conservancy and hydroelectric power projects construction. Diversion channel is as a common method of diversion, just because its such advantages of strong discharge ability and easily meeting the transportation requirements and so on, in todays it has been widely used in large and medium-sized water conservancy projects and hydroelectric power projects. But because of the importance and complexity of construction diversion, whether the diversion programme can meet the requirements of the largest flood and construction during the construction period, this will directly affect the progress of the construction, construction of security, economy and risk have to bear of such key issues. Therefore, we have an urgent need to carry out a in-depth study to meet the requirements of engineering practice.Based on the study of Baojia dam hydroelectric power station channel diversion, according to the basic information provided by engineering units, the hydraulic model was established in the laboratory. Through the model test, a preliminary study of discharge capacity, the water level within diversion channel, velocity, downstream erosion of the diversion channel, and other aspects was carried out, then a reasonable estimation and economic changes were made in accordance with the actual situation.The hydraulic model experiment was conducted on the amendment project to check whether the the amendment can meet the construction phase of construction diversion requirements or not through the revision of the programme, and at last the final package was provided.The results of this test showe that the original project have many restrictions due to the size of imports of drainage and the cross section of diversion channel are too small, so that the biggest flow capacity of diversion channel was just 602.0 m3/s, but at that time the upstream cofferdam water level have reached at the highest of 964.6 meters (top elevation of the upstream cofferdam is 964.5 meters), so it causes serious threat to the safety of the upstream cofferdam, and it is not enough to meet the requirements of the peak flow for 1010 m3/s when the design frequency is 20 persent. The exports erosion of diversion channel is also very serious, when the flow is only 602.0 m3/s, the export velocity is as high as 8~9 m/s, the lowest point elevation of erosion is 935.50 meters, the depth of the scour hole is up to 21.0 meters, so the diversion is not enough to meet the the requirements of the construction period, the original project must be revised as soon as quickly. Through the model tests of proposed amendments and data analysis, the results show that the flow of diversion channel is more stable, it can easily meet the requirements that the largest discharge of flood peak flow which is 1010m3/s one in five years can smoothly reach to the lower reaches of rivers. When the largest discharge of flood peak flow is 1010m3/s, the water level of upstream cofferdam is to 963.73 meters, and the top elevation of the upstream cofferdam is 964.5 meters, the fomer is less than the latter 0.77 meters, so it will not affect the safety of the upstream cofferdam. The exports velocity of diversion channel has decreased, even if the largest discharge of flood peak flow is 1010m3/s, the export velocity of the end of diversion channel flow is also less than 8 m/s, it reduces the extent of erosion to lower reaches of the river and downstream cofferdam, and it also can not threaten the basis of the lower reaches and the downstream cofferdam. Therefore, the amendment project is fully able to meet the requirements of the construction period of diversion.
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