Research And Application On Flood Limited Level Regulation Of Medium And Small Reservoirs In Shanxi Province

In the case of increasing scarcity of water resources, it is one of the important ways to effectively increase the water shortages in Shanxi province and meanwhile has practical and far-reaching significance for the sustainable use of water resources to coordinate the contradiction between water revitalization and flood control, to adjust the reservoir flood limited level, and to give full play to the flood storage in the premise of ensuring the safety. Without consideration of Reservoir's heightening and reinforcement, increasing of the discharge capacity and the new measures of flood control projects in the upstream and downstream, the possibility of flood limited level adjustment mainly comes from the three following aspects:1) the design inflow flood has changed, because of the extension of the hydrological series. So the flood control level can be adjusted on the base of new design flood.2) The original flood season can be staged according to the seasonal variation of storm flood. So the flood control level can be adjusted on the base of new staging design flood in the different stages.3) With the help of update of the modern forecasting equipment and measures, the accuracy of the flood or rainfall forecast improves. This provides the decision-makers an effective forecast period to adjust the flood limited level. On the above three bases, this paper will divide five parts to make analysis against the flood control level adjustment of small and medium reservoirs in Shanxi province.(1)Manual of Hydrological Simulation of Shanxi Province, which was implemented in March 2011, checked the design flood of 12 small and medium watersheds. The result shows that they are lower than the original. Through the calculation of the statistics of Zhangjiazhuang Reservoir on the Manual, this paper shows that both of the peak and magnitude of the design flood are lower than the original value. It acts as a supportive evidence for the conclusion of the handbook. This suggests that all of the design floods of small and medium reservoirs in Shanxi province are excessive and there is possibility to heighten the flood control level.(2)After studying the present three methods of staging reservoir flood season, this paper points out that the study of climate causes can only be used for qualitative analysis, because of its large requisition of data and the complicated watershed situation. In this paper, the threshold selection of mathematical method is too subjective and so does the fuzzy set method because of its consideration of distribution principle in terms of time of the flood season hydrological characteristics. On this basis, this paper holds the view that the flood season staging of small and medium reservoir in Shanxi province should do verification under the data of actual situation and meanwhile set transition period during every stage to ensure a smooth transition of the water level.(3) This paper analyzes the present two views of staging flood control standard. With the help of total probability formula, it proves the view that the staging flood control standard is the same as the annual flood control standard lowers the reservoirs'original standard; it also points out that the view of raising primary flood season control standard to reduce that of the stage is not applicable to the small and medium reservoir in Shanxi, even if it maintains the original standard. It provides a theoretical basis for the calculation of staging flood with the result that the staging flood control standard should be "n" times of the stage "n".(4) After the analysis of the present two calculation methods of stage design flood, this paper points out that the traditional method to calculate the maximum stage design flood reduces the flood control standard and the Frank function modeling method is not applicable to Shanxi reservoirs because it requires too precise samples and is proved to increase the design flood of reservoir in primary flood season. For the small and medium reservoirs in Shanxi province, the author suggests to determine the stage flood control standard with the method of n times of stage n, to determine the design storm value according to the storm frequency curve fitting graph, and to calculate the design flood with the help of " Manual of Hydrological Simulation of Shanxi Province".(5) After analyzing the present two methods of flood limited level control in China, this paper says that the small and medium reservoirs in Shanxi province does not meet the requisition of dynamic control. Based on the available precision of rainfall forecast, the effective flood forecasting period can be seen. So the flood limited level can be raised with the adoption of pre-discharge capacity constraint method.Regard to the disadvantages in this paper, four advices for further research are proposed.