Optimized Construction Flood And Diversion Scheme Of Longkou Project

Construction diversion is a pivotal link that penetrates the whole construction process of hydropower projects. The discharge of construction flood will affect not only the scale of diversion structures but also cost and construction period of the project. Construction flood result calculated with restoring computation of runoff is excessively conservative for construction flood calculation of cascade hydroelectric station, which makes the value of design flood on the high side, the cost of diversion works increasing, and the construction period of hydropower project postponed correspondingly. It is necessary to consider the effect of upstream reservoir adequately and optimize construction flood result with appropriate method in order to reduce quantity of diversion works.There are many kinds of diversion procedures, and an economical & feasible diversion scheme that based on external condition and construction technology, will not only affects the whole construction diversion design greatly, but also concerns the safety and benefit of the project. Comprehensive comparing and analyse must be carried out with several feasible schemes which based on specific condition of the project.Taking example for construction diversion of Longkou hydro-junction of Yellow River, this article puts forward an optimized design method for the design discharge of construction diversion for cascade hydroelectric station and general train of thoughts for comparing of construction diversion procedure.There are two approaches to reduce construction flood discharge of the downstream constructing project. One is to decrease the flood control standard, and the other is to reduce temporarily the limiting level of during flood season upstream reservoir in order to increase its flood control capacity and impound more floods. At present, investigations focus on the method of reducing limiting level during flood season of upstream reservoir and economic comparisons between benefit-loss of upstream reservoir and cost decrease of diversion works so as to select an optimized scheme. In an actual project, many factors will make impact on diversion procedure selection. During selecting diversion procedure, therefore, the designer shall take into account construction period, construction manpower and machine resource, construction condition, the effect to upstream reservoir and the risk borne by the diversion works etc. except for landform and geology condition, hydrologic condition, layout style of permanent works and cost of diversion works.